Beetroot (2004)

Stephen Nottingham

© Copyright: Stephen Nottingham 2004

Contents

4. Cultivation Sowing and Gemination / Thinning and Transplanting / Optimal Temperature Range / Irrigation / Soil Conditions and Nutrition / Pests and Diseases / Crop Rotation / Harvesting / Storage / Seed Crops / Biodiversity / Biotechnology / Bibliography   Cultivated beets (Beta vulgaris) are biennials, although they are usually grown as annuals. Beetroot produces green tops and a swollen taproot during its first growing season. The nutrients stored in the taproot are used to produce flowers and seeds in the second season. Cultivated beets thrive under a wide range of conditions and are easy to cultivate. Beetroot is one of the most popular vegetables grown on allotments and in gardens. It grows quickly, is highly productive, and is usually free of pests and diseases. The cultivation of beet is considered in this chapter, from sowing through harvest, to storage and seed production. This chapter also looks at the conservation of Beta biodiversity and how biotechnology is being used to modify Beta vulgaris. Sowing and Germination The cultivated forms of Beta vulgaris must be propagated from seed. The seed occurs in the form of a seed cluster, glomerule or seedball. As noted in the previous chapter, botanically speaking this is a fruit that typically contains two or three true seeds. Seedballs (hereafter 'seeds') are sown directly into the ground, in the spring or summer, when soil temperatures have risen above 7°C. Deep digging is advised, to obtain a good tilth for the first outdoor sowing in a garden. Around 7 g of seed is generally considered sufficient for 10 m of row. Rows can be drawn with a hoe on a finely raked seedbed. The seeds are big enough to be handled individually. In gardens situations, they can be thinly scattered along the rows or placed about 2 to 5 cm apart in the rows. Beetroot seed is sown at a depth of 1 to 3 cm, depending on cultivar. The seed of early sowings can be sown shallower and denser than later sowings, where later sowings are to produce larger beets for storage. Rows or drills are typically spaced 25 to 45 cm apart. In gardens, for minibeets or where beets are to be harvested very small, rows can be spaced as little as 15 cm apart. Row spacing for the largest maincrop varieties can be up to 50 cm. Once sown, seeds can be covered in loose soil, sand, compost, leaf mould or vermiculite. After sowing and covering, the drills are ideally tamped or patted down to ensure good soil contact with the seeds. Heat, drought and crusting of the soil surface can interfere with germination and emergence. Birds can take seed and re-sowing may be necessary when this occurs. Covering can prevent seed loss to birds. Germination usually takes between 10 to 24 days, depending on temperature and other factors, although under ideal conditions it can occur in less than 10 days. Beetroot germinates relatively well at high temperatures, but germination becomes slow and erratic at temperatures below 7°C. Beetroot seed has a relatively low germination rate compared to other crop seed. The statutory minimum level of germination for beetroot in the UK is lower than for most crops at 70%; although 50% germination is accepted for Cheltenham Green Top, a long-rooted cultivar grown since the seventeenth century. Seed packets usually contain a much higher proportion of live seed, although the statutory testing is done when the seeds are packed for sale and seed viability declines with time. Older seeds will have lower germination rates and beetroot seed should be stored for no longer than five years. Three seed factors that negatively influence germination have been identified: i) a mucilaginous layer that can surround the seedball, ii) the ovary cap, and iii) the presence of chemical inhibitors in the seedball. A mucilaginous layer has been observed on beet seedballs. This is particularly the case for sugar beet, where around 75% of seed can have a significant mucus layer. The germination potential is lowered for cultivars prone to having this layer. In experiments, seedballs with a mucilaginous layer had a lower rate of germination, and a lower level of final germination, compared to seedballs lacking one. The ovary cap or operculum is a dome-shaped structure that covers the embryo. It acts as a barrier to gas exchange. The length of time that the operculum holds fast to the rest of the embryo varies between cultivars. The amount of oxygen available to germinating seeds may be limited in cultivars having tenacious operculum, which can slow development. In experiments where the operculum has been softened through soaking, or has been lifted and removed, germination rate has been increased. The effect is most pronounced for cultivars having a mucilaginous layer. The cork-like layer around the seeds in the seedball contains substances that inhibit germination. These germination inhibitors have been identified as phenolic compounds. They may contribute to the good storage properties of beet seed, and prevent inappropriate germination. However, they can take up to several weeks to de-activate after sowing and result in asynchronous emergence. In an experimental study, seedballs having a mucilaginous layer were found to have higher levels of phenolic germination inhibitors. The three physical and chemical factors outlined above make germination erratic. In commercial operations, a lack of uniformity in germination leads to a lack of uniformity in emergence and subsequent product size. Seed factors affecting germination are therefore considered when planning pre-sowing treatments. Water and temperature are the main environmental factors limiting germination. High water levels in the soil are inhibitory to the rate of germination and emergence. In experiments, however, excess water levels only affected seed viability when associated with high temperatures (above 35°C). Below this temperature, the rate of seed emergence is only slowed down. Excess water restricts gas exchange, reducing the oxygen available to the seeds. Soils that hold water, such as heavy clays, may therefore limit the rate of seed germination more easily than well-drained soils. Methods to boost germination early in the season include warming the soil with cloches, fluid sowing, pre-soaking the seeds, and sowing in modules (transplanting). Cloches or cold frames can be used in gardens to enable the soil temperature for successful germination to be attained earlier in the season. They can be left in place while seedlings emerge. Fluid sowing involves germinating seeds indoors under ideal conditions, for example, in a box on absorbent paper, and then mixing them into a jelly-like medium for sowing. At normal room temperature, around 70% of the seeds of a typical beetroot variety will germinate in six days, after which time they are ready for fluid sowing. This technique is time-consuming, but it enables germination rates to be quantified. The jelly medium protects the germinated seeds from being damaged and it can be made, for instance, out of wallpaper paste mixed at half strength. Germinated seeds are stirred into the jelly medium, which can be squeezed through a nozzle into prepared rows and covered in the normal way. Soaking beetroot seed in water prior to sowing is recommended as a means of improving germination. An hour in water is said to be beneficial, but it is usually recommended that seeds are soaked for up to twelve hours or overnight in lukewarm water or water at room temperature (around 21°C). Soaking acts to wash out the germination inhibitors present in the cork-like layer of the seedball. Some growers suggest using running water to remove the inhibitory compounds from the vicinity of the seeds, but this probably only offers a marginal additional benefit and wastes water. After soaking, the seedballs should be dried before sowing. Most modern lines of beetroot tend to have good germination rates if sown in their year of purchase. In my limited trials with fresh seed of several cultivars, I found that soaking over a period of hours did not significantly improve germination rate. However, this method is likely to be more beneficial when using seed that has been stored for a year or more, with seed of unimproved, traditional or heritage varieties, or when only a small amount of seed is available. The corky layer can be rubbed off beet seed to produce smooth round seedballs. This can help remove the mucilaginous layer and germination inhibitors. In commercial operations, for example, decorking or seed scarification can increase sugar beet seedling vigour. However, for beetroot, rubbing the seedballs can damage the seeds and reduce germination rate. Packets of modern F1 hybrid beetroot seed, in fact, often advise against damaging the seedballs in any way. Successive sowings of beetroot can be made every three weeks during the growing season, to ensure a continuous supply of small beets. Early-season quick-maturing cultivars are planting in spring (e.g. April onwards in Britain). Cultivars that are resistant to bolting are recommended for early sowing. Late maturing larger-rooted maincrop cultivars are sown from mid-summer onwards, and the roots can be stored and used during the winter. It is recommended that the last sowing should be timed at least ten weeks before heavy frosts are expected. Thinning and Transplanting Some thinning is nearly always required for beetroot, because it germinates from multigerm seedballs. If every seed in a seedball germinated, one to three seedlings would emerge per seedball. For the most commonly grown beetroot cultivars, two embryos typically develop to produce two seedlings per seedball. Two or more seedlings can therefore emerge in the same station and adversely compete with each other. Once seedlings are around 5 cm high, they are typically thinned to 5 to 10 cm apart. Single plants of maincrop and long-rooted varieties, however, are thinned to between 20 and 25 cm apart to reach maturity. Dull and damp weather is traditionally recommended for thinning operations. Thinned beetroot can be eaten steamed or in salads. Beetroot mature more quickly when the plant stand is thinner. Monogerm cultivars of beetroot have been bred in recent years, which reduce the time-consuming labour of thinning. They have only one viable seed per seedball and therefore do not need thinning, if only one seed (seedball) is planted per station. Monogerm beetroot cultivars include Monogram, Monopoly and Moneta. All sugar beet seed is now monogerm. In the past, machines were used to thin sugar beet rows after emergence. Today, seeds are sown mechanically using precision drills and there is no need for subsequent thinning. Cultivated beets can be transplanted within modules, so the roots are minimally disturbed. This is sometimes advantageous. The first sowing of the year can be done in seed modules in a greenhouse from February onwards, for instance, to avoid early cold temperatures in the field. Transplanting is usually only recommended for globe beetroot varieties. Modules are planted out, about 10 cm apart, when seedlings are around 5 cm high. Up to three seeds can be sown per module, with thinning leaving the most vigorous seedling. Transplanted seedlings can also be used to fill gaps in rows due to poor germination or seed predation by birds, or to fill odd spaces around an allotment. However, transplanting can on occasion give poor results or malformed roots, and therefore direct sowing is usually recommended as a first course of action where climatic conditions are favourable. Baron von Koppy first transplanted sugar beet, on an experimental basis, in the nineteenth century. This method has been adopted for cultivated beets and is still used today, especially in Japan and China. Chinese gardeners reportedly transplant much of their beetroot early in the season. Beetroot can be grown in modules or boxes in order to harvest the young leaves for salads. These can be grown in compact units, as these plants are not being grown for their roots. Beetroot can also be cultivated to harvest in containers. This works best for smaller globe-shaped beetroot cultivars in containers that are ideally trough-shaped and filled with at least a 20 cm of soil. Optimal Temperature Range Beetroot grows best in a relatively cool and even climate. Temperatures between 15 and 19°C (60-65°F) are ideal for cultivation. Beetroot develops its deepest colours, highest sugar content, and best root quality and shape in this relatively cool temperature range. Beetroot's optimal temperature range is effectively the same as fodder and sugar beet. These cultivated beets prefer cooler temperatures than the wild sea beet from which they are descended. Leaf beets, however, can thrive in warmer temperatures than beetroot. Beetroot growth in early spring is constrained by sub-optimal low temperatures. The use of cloches or horticultural fleece to warm the soil and air around young seedlings can increase early growth rates. The use of horticultural fleece, in one study, increased beetroot yields by up to 50% in early spring. The fleece can be removed four to six weeks after sowing. Temperatures below 10°C (50°F) cause a physiological shift from vegetative growth to reproductive growth, with the storage root shrinking and nutrients being diverted to reproductive structures. If low temperatures persist for over two weeks, particularly with seedlings early in the season, bolting (premature flowering) can occur in the first year's growth. Bolting resistance has been bred into beet cultivars to reduce this problem early in the season. Beetroot can tolerate light to moderate frosts, which can help enhance the sweetness of the roots. However, severe freezing conditions in late autumn and winter can damage the taproot. The roots must therefore be harvested before heavy frosts appear in northern latitudes. Beetroot cultivars with large roots grow best in the colder regions of Central and Eastern Europe, partly because they are more frost tolerant. Temperatures above 25°C (77°F) can adversely affect the growth, colour, and development of beetroot. At higher than optimal temperatures, the storage of nutrients in the roots is reduced, leading to smaller root size, and impaired texture and flavour. Roots can become stringy and tough in response to excessive heat. Some cultivars are more tolerant of tropical conditions than others, however, and these are recommended in warmer regions. Crimson Globe and Detroit Dark Red, for instance, are cultivars that do well in warmer climates. Irrigation Cultivated beets can survive drought and salinity better than most crops. This reflects the species' coastal origins. However, supplying additional water can raise crop yield. The main aim of irrigation in cultivated beets is to maximize productivity, by enabling an even growth pattern to occur throughout the season. Maintaining moisture levels early in the season is important, but overwatering is detrimental to growth. Beetroot generally requires less water than leaf beets. Frequent watering of beetroot leads to increased leaf growth, but this is not necessarily accompanied by a proportional increase in root growth. Overwatering can lead to excessive leaf growth and small roots. Waterlogged soils can harm root development, encourage disease, cause minerals to leach away from the roots, and create harvesting difficulties. The leaves of waterlogged beetroot can turn red and photosynthesis can be affected, resulting in plants that stop growing for a period of time. Moderate watering is therefore advised, sufficient to prevent the soil from completely drying out. In wet conditions, growing beetroot in raised beds enhances drainage. Mulching can conserve soil moisture during dry weather. Dry conditions over a period of weeks may constrain plant growth and reduce yields. In dry soils, there is an increase in the amount of zoning in the roots. Paler rings develop due to the lack of moisture, while the roots start to become woody. Sudden irrigation or rain after a period of drought can cause roots to split. Watering at a rate of eleven litres per square metre every two weeks is recommended in the Royal Horticultural Society (RHS) Encyclopedia of Gardening. Water is taken up by the fibrous roots that grow from the main storage or taproot. Deep-rooted (long root-shaped) beetroot cultivars and sugar beet can access water deeper in the soil and survive drought better than shallow rooted (e.g. globe-shaped) cultivars. Irrigated sugar beet produces higher sugar yields. Similarly, the natural sweetness in beetroot is enhanced in plants that have been adequately watered. Soil Conditions and Nutrition Cultivated beets are tolerant of a wide range of soil conditions, but they grow best in open sunny sites on well-drained light, moist, friable and fertile soils. For beetroot, deep sandy loams are ideal, especially those with a high organic content, which supplies natural fertilizer and retains its moisture. Rich moist fertile soils produce the best roots, although heavy clay soils may hinder root development. Although beets can be grown under most conditions, for optimum or profitable yields the application of fertilizer or lime is sometimes required. In particular, sufficient levels of nitrogen, sodium, potassium and phosphorus are needed to ensure good growth. As with all such operations, the cost of external applications should be considered in terms of the added value to the crop. The application of fresh manure, however, is not recommended when preparing the ground for beetroot, because it can induce the formation of multi-fang or thong-like roots instead of a single thick and symmetrical taproot. Heavily manured or too-rich soils can also induce cultivated beets to bolt. Soil pH The relative acidity or alkalinity of a soil is measured using the pH scale. A neutral soil has pH 7.0, acid soils have a pH below 7.0 and alkaline soils have a pH above 7.0. Beetroot prefers neutral to slightly alkaline soils. Beetroot thrives when pH is between 6.0 and 8.0. However, lime should be applied to acid soils below around pH 5.8, as root growth can be constrained. Beets are less tolerant of soil acidity than crops such as beans or maize. However, beetroot is more tolerant of alkaline soils. Nitrogen Nitrogen (N) is the most important fertilizer element applied to beets in commercial production, because it is the element most likely to be deficient in arable soils. Nitrogen is particularly important for healthy top growth, improving the vigour and colour of foliage. In sugar beet production, this is additionally important because many mechanical harvesters need to handle the tops to lift the roots. There is no single characteristic symptom that identifies nitrogen deficiency. However, the foliage typically becomes light green in appearance, then yellow, due to the disappearance of chlorophyll from the leaves. This reduces photosynthesis and subsequently crop yield. In sugar beet, nitrogen deficiency is often observed in patches of stunted plants with small yellowing leaves. Nitrogen deficiency in beets is most likely to occur on sandy or gravely soils. The application of nitrogen fertilizer can greatly increase yields, particularly on continually cropped soils. However, in sugar beet, excessively high levels of nitrogen can reduce the quality of roots in terms of their sugar content. This is the biggest dilemma of sugar beet nutrition: crops benefit from additional nitrogen, but too much can depress the sugar yield and increase the proportion of impurities in the extracted sugar. In garden situations, enough nitrogen is usually supplied by an organic-rich soil. Otherwise, nitrogen fertilizer can be applied in moderation before sowing beetroot seed. Nitrogen can be put on as sodium nitrate (nitrate of soda) in slightly acidic soils, or where available sodium is limited. Sodium Sea beet typically grows in stony and sandy soils along coastlines. Such soil conditions are still favourable by cultivated beets, although the beets that have been selected for their taproots do best in soils with fewer stones. In keeping with its seashore origin, beetroot tolerates moderate concentrations of salt. Uniquely among crops, beets take up and use large quantities of sodium (Na), which is required for optimal growth. Beta vulgaris, particularly in its wild form, is regarded as a halophyte. Common salt (sodium chloride) is applied on beetroot in some areas as a fertilizer. Salt stimulates beetroot growth and kills small weeds, which are generally less tolerant of salt than beetroot. However, the application of salt on beetroot growing in heavy clay soils is not recommended. Beetroot and sugar beet are among the few commercial crops that can be grown in saline conditions, although it is difficult to obtain uniform plant stands. There are no obvious sodium deficiency symptoms, but plants deficient in sodium are far more likely to show symptoms of potassium deficiency. Potassium High levels of potassium (K) are required for optimum growth of beet roots. The symptoms of potassium deficiency are often referred to as ?scorch?. Patches of dead tissue occur in leaves (chlorosis), which take on a dull olive green to bronze appearance. Low sodium exacerbates the problem, while potassium deficiency can be alleviated by the addition of both potassium and sodium to the soil. Potassium fertilizers can be applied in bands beneath rows prior to sowing seed or alongside seed soon after sowing. Slow-release fertilizers may be applied in the weeks before sowing. Potash fertilizers are often recommended prior to sowing and Arthur Hellyer, in his gardening guide, suggests an application of one part sulphate of ammonia, one part sulphate of potash, and five parts superphosphate of lime, mixed and applied at 100-130 g per square metre. Wood ash is also beneficial, forked into the ground prior to sowing. Phosphorus Phosphorus (P) is necessary for vigorous early seedling growth in cultivated beets. It is often in short supply in newly cultivated soils, but builds up in soils after repeated fertilizer applications. Phosphorus deficiency is therefore rare and only occurs when soils are extremely depleted of this element. It is particularly uncommon in mature plants, but manifests itself in seedlings through stunting and dark-green or purple-red leaf colour. In older plants, the roots can also become stunted, while the taproot may form a mass of fibrous secondary roots. Commercial fertilizers often deliver several key elements simultaneously, for example, N, P, K fertilizers. In garden situations, however, in most cases adequate beet crops will be produced without recourse to fertilizers. Sulphur Sulphur (S) is absorbed by plants in the form of sulphates. The symptoms of sulphur deficiency are yellowing young leaves with irregular brown blotches. However, enough sulphur usually falls on crops in rain, especially in polluted regions. Sulphur deficiency is therefore rarely a problem in cultivated beets. Calcium Calcium (Ca) is an important element for cultivated beets, although it tends to be overlooked as it is usually found at sufficient levels in the soil. It accounts for why cultivated beets preference for slightly alkaline soils and their intolerance of acid soils. The most characteristic symptom of calcium deficiency in cultivated beets is tip-burn, with young leaves becoming crinkled and reduced in size, and the growing point developing abnormally so that lateral shoots appear. This deficiency is not caused by inadequate calcium in the soil, but by the plant's inability to take it up. This can occur in acid or saline soils, or soils that have been waterlogged with salt water. Calcium can be added to the soil in the form of lime to redress the nutrient balance. Magnesium If levels of N, P and K are adequate in sugar beet, another nutrient that might be limiting yield will sometimes be magnesium (Mg). Intensive cropping removes this element from soils. The symptoms of magnesium deficiency are pale yellow and brittle necrotic areas in leaves (the latter distinct from the softer dead tissue areas seen in potassium deficiency). Magnesium deficiency is most likely to occur in hot summers for crops growing on sandy soils. Boron The most frequent nutrient deficiency encountered in cultivated beets is boron (B) deficiency. A deficiency of this micronutrient is also referred to as black spot, heart rot, dry rot or canker. Boron deficiency results in stunted plants, the deformation and death of the growing point, and slow growth. The crown of the root becomes hollowed and blackened, due to water accumulation. Rough black spots can appear on the roots. In beetroot, this gives the roots a bitter taste. The roots may eventually become entirely discoloured, hollowed or split. The yield and quality of cultivated beet roots can therefore be severely affected. Boron deficiency can also result in corky growths on the shoots and stalks. Roots from boron deficient plants store poorly. Boron deficiency arises due to either a lack of boron in the soil or an inability to take it up from the soil due to unsuitable growing conditions. A lack of moisture aggravates boron deficiency, and it most commonly occurs on chalky or heavily limed soils that have dried out. Maintaining moisture levels in the soil and avoiding excessive liming helps plants to obtain boron from the soil. Small amounts of borax (sodium borate) can be added to the soil to alleviate problems caused by boron deficiency. Alternatively, sprays of borax solution can be applied to the foliage. However, the application of too much boron may be toxic to subsequent crops. Plants that naturally accumulate boron, such as sweet clover, can also be used to enrich the soil, particularly when they are grown as a green manure. Seaweed is used as a valuable source of green manure on cultivated Beta vulgaris in coastal areas. Manganese and other trace elements A deficiency of manganese (Mn) in the soil causes yellow or necrotic blotches to occur between beetroot leaf veins. This mainly affects older leaves and is most prevalent in very alkaline soils. It can be cured by the addition of fertilizers containing manganese. A number of other micronutrients or trace elements are required for the optimum growth of cultivated beets. The main ones being chlorine (Cl), copper (Cu), iron (Fe), molybdenum (Mo) and zinc (Zn). These are rarely deficient in soils using for beet cultivation. The presence of nutrients and micronutrients in cultivated beets helps to make them such health-promoting vegetables (see Chapter Seven). Pests and Diseases CAB International?s Crop Protection Compendium lists 67 major pests of cultivated Beta vulgaris. These include weeds, insects, nematodes, and fungal and viral pathogens. Cooke (1993) lists 56 types of sugar beet pest, excluding weeds. However, pests of cultivated Beta vulgaris are largely sporadic in their impact. Beetroot under normal circumstances has relatively few pest or disease problems. Weeds Weeds compete with beetroot for space, light, water and nutritional resources in the soil, particularly during the early part of the season. They can reduce yield if left unchecked. Regular hoeing in gardens and allotments prevents weeds competing with beetroot. When hoeing, care should be taken not to damage the roots. Applications of weedkillers (herbicides) provide control in larger-scale and commercial plantings. The weeds in the CAB International listing include amaranth or pigweed (Amaranthus retroflexus), chickweed (Stellaria media), cleavers (Galium aparine), dandelion (Taraxacum spp.), Johnson grass (Sorghum halepense), knotweed (Polygonum aviculare), nettles (Urtica spp.), meadowgrass (Poa annua) and ryegrass (Lolium spp.). In sugar beet, 70% of weeds are typically broad-leaved plants and 30% are grasses. It is plants in the Chenopodiaceae or goosefoot family, however, that are the major weed pests of cultivated Beta vulgaris. This is not surprising considering that Beta vulgaris is itself is in Chenopodiaceae. Plants in this family tend to thrive under similar conditions. Fat hen (Chenopodium album) is probably the biggest weed problem in sugar beet and beetroot. Weedy forms of Beta vulgaris or 'weed beets' have in recent years become a particular problem in sugar beet fields, especially in France and the more southern areas of Europe. Weed beets can be bolters (prematurely setting seed in their first year?s growth without producing useful roots), plants self-seeded from previous cultivation or hybrids. Hybrid weed beets result from pollination between beet plants growing wild around agricultural land and sugar beet crop plants. They tend to adopt an annual growth pattern, competing with the crop for resources and bolting to spread seed that furthers the problem. Weeds are a particular problem early in the growing season, when they compete for resources (e.g. moisture, light, soil nutrients) with beet seedlings. Herbicides are sprayed predominantly at this time to control weeds. However, weeds in the Chenopodiaceae and, in particular, weed beets respond to particular herbicides in the same way as cultivated beets. They are difficult to control because the herbicides that control them best can also damage crop plants. The control of such weeds has been a desirable goal in commercial beet production. This is why the first transgenic or genetically modified Beta vulgaris was sugar beet modified to be resistant to particular herbicide groups (e.g. glyphosates). Transgenic herbicide-resistant sugar beet can be sprayed with these herbicides, thereby controlling weeds without damaging the crop. This has provided great benefits to sugar beet growers. However, concerns have been expressed about the environmental impact of the changed herbicide spraying regime and the evolution of resistance in weeds to the herbicides that are being repeatedly sprayed on transgenic crops. Nematodes The beet cyst nematode (Heterodera schachtii) was one of the first pests observed to limit sugar beet yields. It was described in the 1880s, in beets grown in short rotations in Germany. Beet cyst nematode is now a major pest of sugar beet worldwide, and is also a pest of fodder beet and beetroot. It invades the roots, stunting their growth. Resistance to beet cyst nematode has been bred into modern lines of sugar beet through the transfer of genes from the wild species Beta patellaris (in the section Procumbentes of the genus Beta). Root knot nematode (Meloidogyne incognita) and species of stubby root nematode (Trichodorus spp.) adversely affect the roots of cultivated beets, particularly early in the growing season. Stubby root nematodes cause the roots to fork or fang. In commercial and garden situations, lengthening the rotation is the best method to reduce damage due to nematodes. Insects No single insect pest consistently attacks cultivated beets. However, a range of species can potentially damage them. This occasional damage can be severe. Many of the insects attacking beets occur in the family Lepidoptera (moths and butterflies). Larvae of beet webworms (e.g. Hymenia perspectalis, Loxostege sticticalis and Spoladea recurvalis) feed on leaves and roots. They construct a protective shelter by rolling a leaf and tying it together with webs. Cutworms (e.g. Agrotis spp. and Peridroma saucia) are noctuid moth larvae that feed on the lower leaves and crowns of beet roots. After attack by cutworms, the stem bases and lower leaves are visibly gnawed. Beet armyworm (Spodoptera exigua) larvae can defoliate crops in the USA, especially when migrating from pigweed. Lepidoptera larvae can be picked off cultivated beets and destroyed in gardens and small-scale commercial operations. Flea beetles (e.g. Chaetocnema confinis) are small jumping beetles, which eat holes in young leaves and can seriously damage seedlings. The white larvae of beet leafminers (e.g. Pegomya hyoscyami) feed on internal leaf tissue, causing yellowish blisters on the foliage. Heavily damaged leaves can be picked off and destroyed to prevent infestation spreading, although leafminers do no damage to the roots. Aphids (e.g. Aphis fabae and Myzus persicae) form dense colonies on the shoots and leaves of Beta vulgaris. They can cause direct damage by feeding and extracting plant sap, but are primarily a pest of beets because they act as vectors for virus yellows diseases. They transmit virus from crop to crop and spread it within a crop. Aphid species are particularly significant as pests of beetroot being grown for seed. Controlling aphids with insecticides is the main method of preventing virus infestations in sugar beet. However, heavy insecticide use has resulted in aphids evolving insecticide resistance, which has led to a resurgence of virus disease problems in sugar beet. The beet leafhopper (Neoaliturus tenellus [Circulifer tenellus]) is a pest of beetroot because it transmits beet curly top virus (curly top disease). The beet leafhopper and the virus it transmits are primarily found in the USA. Viral diseases Virus yellows is a group of aphid-transmitted viral diseases that affect all cultivated beets. Virus yellows was first described in the 1930s affecting sugar beet. It causes foliage to become yellowed or necrotic. Leaf veins may be particularly affected. This reduces photosynthetic efficiency, root system development, and sugar yield and quality. It was subsequently found that virus yellows comprises a complex of closely related viruses: beet yellows virus (BYV), beet mild yellowing virus (BMYV) and beet western yellows virus (BWYV). These viruses have different distributions and slightly different symptoms. They are rarely a problem in beetroot. Beet mosaic virus (BtMV) is another aphid-transmitted beet virus. It causes flecking and mosaic patterns on beet leaves, and eventually major leaf abnormalities. Curly top disease is caused by beet curly top virus (BCTV), which is transmitted from plant to plant by feeding beet leafhoppers. The symptoms of curly top disease include warty leaf veins and rolled, brittle and twisted foliage. Plants become stunted and the root system is reduced in size. Curly top disease caused major losses in sugar beet in the USA, until the introduction of resistant varieties in the 1930s. Today, all sugar beet cultivars incorporate resistance to curly top disease. Not all beet viruses, however, are transmitted by insect vectors. Some minor viruses of sugar beet are transmitted by nematodes, and one significant pest problem arises through an association between a virus and a fungus. Beet rhizomania is caused by the beet necrotic yellow vein virus (BNYW), which is transmitted by the fungus Polymyxa betae. Rhizomania is largely restricted to species of Beta because of the narrow host range of the fungus. The disease was first described in Italy in 1952, and it is now widespread. Rhizomania can cause severe yield losses in sugar beet. The virus was named after the leaf symptoms, but the major economic damage is done to the roots. Rhizomania (meaning leaf madness) is characterized by the abnormal proliferation of lateral roots, producing a mass of fibrous roots known as bearded root. Fungicides have provided the main means of control for rhizomania in sugar beet. However, resistance has been found in wild Beta species that is being incorporated into breeding programmes, and genetic engineering techniques are being used to produce 'immune' plants through the incorporation of viral coat proteins in the plant genome. Fungal pathogens There are a number of fungal diseases that affect cultivated beets, including mildews and the organisms that cause damping off, scab and leaf spot. Downy mildew (Peronospora farinosa) causes red-rimmed spots on the leaves of beetroot. It thrives during periods when the roots dry out or when plants are growing slowly, and spreads quickly in the field during cool and humid weather conditions. Downy mildew affects the tops of beetroot, causing discolouration. It can spread to the crown and top of the taproot. It can also infect the flowers and seedball, and it is a seed-transmitted pathogen. Powdery mildew (Erysiphe betae) has symptoms similar to downy mildew. The fungi that cause both downy and powdery mildews in cultivated beets are restricted to Beta species. Resistance to powdery mildew has been bred into sugar beet using genes from sea beet (Beta vulgaris subsp. maritima). A range of different soil-born fungal pathogens cause damping off or blackleg in cultivated beets (e.g. Pleospora betae, Pythium ultimum and Phytophthora spp.). Seedlings and young plants rot at soil level, collapse and die. Damping off is most prevalent in wet weather, in early spring plantings, and in poorly drained soils. It is rarely a problem in sugar beet today, because of the use of fungicides and resistant varieties. Individual rots are often distinguished within this general condition, including rhizoctonia disease (Rhizoctonia solani), wet rot (Phytophthora megasperma), phoma (Phoma betae), violet root rot (Helicobasidium purpureum), sclerotium root rot (Sclerotium rolfsii) and others. Scab (Streptocyces scabies) affects many vegetables, including cultivated beets. Beetroot is particularly susceptible to scab, which causes rough corky spots and warty growths on the skin of the root. It can be prevented by ensuring that soil pH is near neutral and by rotating crops. Cercospora leaf spot (Cercospora beticola) is a widespread and destructive foliar disease of cultivated beets. It is one of the most common diseases affecting beetroot and can cause significant economic losses in sugar beet. Cercospora causes small brown spots with reddish-purple borders to appear over leaves and stems. Heavy infection causes leaves to become yellow and drop off. Applying potash before sowing can help prevent leaf spot, as can crop rotation. Resistance to Cecrospora leaf spot was first bred into sugar beet in the 1920s by Italian scientists, through crosses with resistant sea beet. More recently, beetroot cultivars have been bred with resistance to Cercospora leaf spot. Leaf spot in beetroot can also be caused by other fungi (e.g. Ramularia beticola). Leaf spot is more prevalent in wet conditions when plants are closely spaced. Slugs and snails Molluscs can do considerable damage to the foliage of cultivated beets, particularly those grown in gardens and allotments. Slugs (e.g. Deroceras reticulatum) make holes in the leaves, especially when conditions are damp on heavier and poorly drained soils. Slugs can be a particular problem when roots are left in the ground late in the season. Snails can also, on occasion, be a problem under wet conditions. Birds and mammals Birds eat beetroot seed and seedlings. Sparrows (Passer spp.) can be a problem in gardens, while pheasants (Phasianus spp.), partridge (Perdix perdix) and pigeons (Columba spp.) are among the main bird pests in sugar beet fields. Netting can keep birds away from seed and seedlings in gardens and allotments. Birds can eat their way down a row of seeds, but not all the seeds are necessarily destroyed. Charles Darwin, in The Origin of Species (1859), records beet seed germinating after passing through the digestive system of birds. He fed seeds of various crop plants to birds of prey in the Zoological Gardens in London and noted that two beet seeds grew after having been retained by a bird for two days and fourteen hours, respectively. This represents a minor route by which wild and weedy Beta vulgaris can disperse. A number of mammals are pests of sugar beet, including moles, mice, rats, rabbits and deer. Much of the damage caused, however, is non-lethal defoliation from which plants can recover. Crop Rotation Rotating crops is an important factor in reducing the incidence of pests and diseases in cultivated beets. Yields of sugar beet were significantly reduced by nematodes, for instance, before the practice of rotation became established. Rotation, in combination with crop hygiene, is particularly important in reducing the incidence of damping off, rot and other fungal diseases. Beetroot can easily be fitted into planting schemes in a garden or allotment, for example, being sow on ground from which heavily manured crops like potatoes or beans have recently been harvested. By following on from a well-manured crop, beetroot can be grown in soil with good water-retention properties. Green crops and potatoes are demanding of nitrogen in the soil and benefit from well-rotted animal manure. Fresh manure is harmful to root development in beetroot and crops such as carrots, turnips and parsnips. Therefore, green crops and potatoes are typically followed by root crops in crop rotation systems. Rotation in a three or four year cycle with legumes is usually recommended for cultivated beets. A three-year garden rotation could involve, for instance, firstly, the rotation of blocks of cabbages and other brassicas along with lettuces and other salads; secondly, potatoes followed by broccoli and other winter greens; and thirdly, carrots, beetroot and other root crops, along with peas and beans. A number of companion plants to grow with beetroot are suggested in The Complete Book of Vegetables, Herbs and Fruit. Beetroot is said to flourish in the company of kohlrabi and brassicas, carrots, cucumbers, lettuce, onions and most beans, but not tall runner beans that could shade them. Dill or Florence fennel planted nearby may attract predators that prey on insect pests of beetroot. Beetroot combines well with many other crops and is quick growing, making it good for serial cropping and intercropping within a rotation. Harvesting Beetroot are harvested from the early summer to late autumn in their first year of growth. The roots can be harvested over a period of time, to give beets ranging in size from small to large and mature. It usually takes around 60 to 90 days for beetroot to reach full maturity. Beetroot can be harvested when required and left in the ground until the first heavy frosts of autumn. Mature roots can survive mild frosts, but can suffer freezing damage during heavy frosts. The leaves start to fall away from an upright position when beets reach maturity. Beetroot must be lifted carefully, because bruised and broken roots bleed and are of diminished culinary value. Beetroot or garden beet is usually harvested with its leaves by hand, and either used domestically or sold fresh in bunches tied around the stems or leaves. For market sale, dead leaves are usually removed and the roots washed, for example under a hosepipe, rather than being scrubbed. The leaves are traditionally twisted off above the crown. If the leaves are not wanted in the kitchen, their high mineral content (e.g. magnesium) makes them a useful addition to the compost heap. Small beets or minibeets (below 5 cm) may be harvested about two months after sowing, while mature full-size beets may be harvested after three months or longer. Final root size is due to variety and spacing, and not degree of maturity. In southern Europe, beets can be left in the ground overwinter. In mild climates, a layer of straw around 15 cm thick can be placed over the soil where roots are left in the ground overwinter. In northern latitudes, where most beetroot is now grown, the beets must be lifted and stored before midwinter, because of potential damage from severe frosts. In commercial operations, beetroot and sugar beet are mechanical harvesting in bulk. The first mechanical harvesters for cultivated beets were introduced in the 1930s in the USA. By the 1950s, the entire US sugar beet crop was harvested mechanically. Little sugar beet worldwide is now harvested manually. Single or multiple-row harvesters are available, which operate using two different methods. Beets can be lifted mechanically using the tops. Good top development is encouraged in beets harvested by this method. In the other method, a flail removes the tops prior to harvest. The beets are then harvested from the soil like potatoes. This method can be used on modern beet cultivars having small top development. Eastern and Central Europe has historically been associated with the large-scale cultivation of maincrop beetroot. The major beetroot producers today are Russia, Poland, France, Italy and the USA. Northern Europe and North America produce the bulk of the commercial crop. Their combined commercial production (excluding Eastern Europe) is around 900,000 tons, according to CAB International figures. In most other areas, beetroot is mainly grown in market gardens or for home consumption. In Eastern Europe a large proportion of the beetroot crop is home-produced. In Russia, for instance, family dachas (small country houses and gardens) are used to grow beetroot and other vegetables. Recently, a travel company offering coach trips between St. Petersburg and Moscow started operating under the name Beetroot Bus Tours, because of the prevalence of beetroot fields en route. The major areas of beetroot production in the USA are New York, Wisconsin, Oregon and Texas. Most US beetroot goes straight to the food processing industry, but some reaches the fresh market. The commercial crop is harvested mechanically, but the crop for the fresh market is often hand harvested. Mechanical harvesters first cut off the bulk of the leaves and then crop the plants within around 5 cm of the crown, with a second harvester following to lift the roots into bulk trailers. Around 14,000 acres of beetroot were grown annually in the late 1990s in the USA. Figures from the University of Georgia show that processed beet yields 18 to 25 tons per acre, while fresh market beet yields 140 to 200 cwt. per acre. Commercial beetroot fall into three grades for the US market; grade 1 being below 5 cm (up to 2 5/8 inches) in diameter, grade 2 being around 5-7 cm (2-2 5/8 inches) and grade 3 being around 7.5-10 cm (3-4 inches). Grade 2 beets are consistently available season long, but grades 1 and 3 have greater seasonal variation. For beetroot sold fresh, the USDA (United States Department of Agriculture) set a maximum permissible weight loss of 41% from harvesting to point of sale, although this is 7% if roots are sold with tops as the leaves soon wilt due to moisture loss. In garden situations, Hellyer estimates that beetroot typically yield around 2.5 kg per square metre or 1.3 kg per metre of row. CAB International data gives typical commercial yields of around 15.3 t/ha of beetroot in Mediterranean and tropical conditions. The world's single heaviest beetroot, according to the Guiness Book of Records, weighed 23.5 kg (51 lb 9.4 oz) and was exhibited by Ian Neale at the National Giant Vegetable Championship, Shepton Mallet, in Somerset, England, on 7th September 2001. Storage Beetroot, fodder beet and sugar beet store well and are amenable to long-distance transport. Fully mature beets store better than immature roots. Beets have traditionally been stored outdoors on farms, in covered heaps or buried in hogs or clamps. Fodder beets have often been stored in bulk in silos. However, when grown commercially, beets are now moved indoors and stored under controlled environmental conditions. Beetroot needs around 12 to 16 weeks of growth to reach a sufficient maturity for storage. Long and cylindrical rooted cultivars are usually considered better for storing when mature, while cultivars with globe-shaped roots are considered better for immature use, but all beetroot cultivars store reasonably well. Before storing, the leaves are either twisted off or cut 5 to 8 cm above the crown. Beetroot can be stored in strong boxes in sand, earth, or sawdust, in a cool, frost-proof location. Under favourable conditions, beetroot can be stored up to five to six months. The best storage conditions for beetroot, described in Stanley Kay's Postharvest Physiology of Perishable Plant Products, are in cool temperatures (0 to 5°C) and high humidity (90 to 95% relative humidity). High humidity is important because the maximum acceptable loss of water is 7% from stored roots, or 5% when beetroot is bunched with leaves, before beets are considered unmarketable. Beets (no leaves) are comprised of around 88% water. High humidity minimizes water loss during storage. The freezing point for topped beetroot, with leaves removed, is -0.9?C, while for bunched beetroot is it -0.4°C. Below these temperatures, freezing damage will occur. High levels of carbon dioxide may also be detrimental to beetroot storage. In high levels of carbon dioxide (30-70%), beetroot increases its respiration rate, which leads to a higher metabolic rate. Storage methods utilizing high carbon dioxide are therefore inappropriate for beetroot, while some degree of air circulation that prevents carbon dioxide from building up may enable beetroot to be stored for longer. Topped beets for the fresh market in the USA are typically graded, washed and packaged in polyethylene bags. They are stored for up to five months at below 5°C (around 32°F) and 90-95% relative humidity before being sold. Beetroot should not be stored in large bulk, but ideally in pallets or crates that allow good air circulation around each beet. These are mostly marketed within six months, enabling the crop to be sold throughout autumn and winter. If beetroot is to be kept for longer, preservation is required. Commercially grown beetroot is mainly preserved before sale, by being either boiled or pickled. In the USA, boiled and canned beets are common, while in Europe, mini-beets or sliced beetroot pickled in glass jars is more prevalent. The Germans and British, in particular, consume large quantities of beetroot pickled in malt vinegar. Industrial processing involves cleaning, slicing or dicing; then steaming or boiling, which cooks and sterilizes the beets; followed by mechanical skinning. The beetroot are then vacuum-sealed in a preserving solution such as vinegar. During World War II, beetroot was found to be one of the most satisfactory dehydrated vegetables for military and civilian use. It can still be bought in freeze-dried form in health food stores, because beetroot is undergoing a revival as a health tonic (see Chapter Six). Seed Crops When beetroot is grown as a vegetable, it is treated as an annual and harvested after the first growing season. However, to produce seed, it must be allowed to complete its two-year life cycle. When raising beetroot for seed, the crop can be sown in spring or early summer and grown normally during its first season. Beetroot requires a cooling period (vernalization) at the end of the first season's growth before it will flower in the second season. Beetroot seed is produced commercially in colder climates, in northern Europe and North America, so that this period of cooling is easily achieved and where pest and disease problems are minimized. In temperate areas, two weeks at between 2 and 10°C should induce flowering. For seed production, beets are lifted at the end of the first season and the best material is selected. These roots are stored in sand or earth in a cool but frost-free place. They are then planted out in the following spring and allowed to grow until they produce seed. The guidelines of the Heritage Seed Library, part of the Henry Doubleday Research Association (HDRA), suggest replanting roots of beetroot in blocks with plants 30 cm apart. The crowns are positioned at soil level and watered well to encourage re-rooting. Beetroot is self-incompatible and will not self-fertilize. Therefore, blocks or rows of beetroot of the same cultivar are necessary to produce seed. Different beetroot cultivars should also be isolated when grown for seed to avoid hybridization and maintain varietal purity. Although pollination is mainly by wind, Beta vulgaris flowers produce nectar and are visited by insects. In gardens, where large isolation distances are often not possible when seed saving for personal use, horticultural fleece can be used to isolate blocks of flowering plants to help reduce cross-fertilization. Sugar beet seed production is an industry in itself. Plants that are used to produce seed are known in their first year as stecklings. These are carefully chosen from the available plants. Stecklings are harvested and stored without tops like other sugar beet, but are then mechanically transplanted into different fields to begin a second year's growth. Alternatively, the roots can be left in the ground to overwinter after the first year's growth, with the plants being allowed to grow on into their second season. This can only be done in northern latitudes where the temperatures become cold enough for vernalization, but is a method that significantly reduces labour costs. As the second year's growth begins, the main shoot tip is removed to encourage side branching, which increases the number and quality of the seed produced. All the cultivated forms of Beta vulgaris (e.g. leaf beets, beetroot and sugar beet) can readily interbreed. Wind-born pollen can fertilize beet flowers over long distances. Commercial seed crops of beetroot, therefore, are often grown several miles away from sugar beet or fodder beet seed crops because cross-pollination could ruin seed purity for one or other crop. Minimal isolation distances of up to 3,200 metres have been stipulated for sugar beet seed crops in order to maintain varietal purity during seed production. In the UK, for example, the Beet Seeds Regulations 1985 (as amended in 1989) state that the minimum distances from neighbouring plants for the production of seed for sugar beet and fodder beet should be 1000 metres away from other Beta vulgaris pollen sources. The flower spike is harvested when all the seedballs have fully developed. The seedballs are removed by pinching them off the stalks and they are stored intact. The HDRA guidelines suggest that beetroot seed can be stored for up to six years under cool dry conditions. Seed production is difficult under tropical conditions, so seed is imported into many countries where beetroot is now grown. A recent theory suggests that the location on the flower spike from where seeds are harvested may be significant. Research in China has found that wheat seed collected from the centre of the spike grows into plants that have significantly higher yields than wheat plants grown from seed collected from the top or bottom of the spike. Stephen Coleman has suggested that this might also apply to other crops having seeds spaced out along spikes. Seed position on the spike of Beta vulgaris, for instance, may have been a factor in the differentiation of this species into different cultivated forms selected for either top or root growth. Localized selected seed experiments with Beta vulgaris may become an interesting area of exploration. Biodiversity Crop biodiversity is preserved in situ, especially in a crop?s centre of origin and genetic diversity, in seedbanks, botanical collections and gardens. Seed saving organizations around the world are playing an important role in preserving traditional, heritage or heirloom crop varieties. The Heritage Seed Library of the HDRA in England, for example, maintains seed for many crop varieties that are no longer registered for sale in seed catalogues. The Heritage Seed Library maintains several traditional beetroot varieties, which are available to amateur gardeners on paying a subscription to the library. Because European Union (EU) legislation states that seeds not listed on National Seed Registers cannot be sold, seeds for many heritage varieties must be swapped or exchanged in this manner in order to preserve crop biodiversity. It is important that heritage varieties continue to be cultivated. Agriculture is culture in all its aspects. History is present in heritage varieties. A garden of traditional and heirloom varieties is a fascinating living museum. It offers clues to how our ancestors lived and how they improved food plants, and it propagates a unique aesthetic beauty. Beetroot has in the past, for instance, been grown for its ornamental value far more than it is today. Varieties that have dropped out of fashion as food plants still look beautiful in gardens. The taste of traditional varieties is also different to modern cultivars, which like all horticultural crops are today mainly bred to satisfy the demands of intensive agriculture, food processors and supermarkets. Heritage varieties offer a unique genetic resource for future generations. Genes from them, for instance, may encode traits that may be beneficial against emerging pests and diseases or to help crops adapt to climate change. A rich genetic heritage of wild Beta vulgaris and related Beta species still exists in Europe. However, many of the natural habitats where these plants occur are under threat. It is important to preserve this genetic material in its natural habitat, within in in situ conservation projects, as well as in seed banks and botanical collections. Within the genus Beta, species in the section Procumbentes are largely restricted to the Canary Islands, where tourism is a threat to genetic diversity through habitat destruction. The only species in the section Nana (Beta nanae) is restricted in distribution to snowy patches above 2000 metres on several Greek mountains. Nature reserves will be needed for its long-term survival. Several Beta species in the section Corollinae are potentially threatened in central Asia, for example, by changing farming practices. Meanwhile, in the section Beta, populations of the perennial species Beta patula are mainly found on a small island near Madeira; while an unusual polyploid strain of Beta macrocarpa is restricted to salt mine workings in the Canary Islands, which are vulnerable to pressures from tourism. Germplasm from wild Beta species has already been used to make improvements to sugar beet in terms of pest and disease resistance. It is therefore important to preserve all existing germplasm within the genus Beta for future breeding programmes. An International Data Base for Beta (IDBB), funded by the European Commission, is in the process of being established (2004), which will facilitate access to germplasm held in a decentralized network of genebanks around the world. Molecular marker techniques will be used to look for novel and potentially useful genetic diversity, while material will be evaluated for resistance to root rots and fungal pathogens, viral diseases, and for tolerance to saline and drought conditions. Sugar beet breeders in Europe and North America maintain collections of wild and cultivated Beta vulgaris from its area of origin in the eastern Mediterranean, and from its secondary centres of diversity. The International Board for Plant Genetic Resources (IBPGR) has given Beta vulgaris high priority as a species needing preservation, due to a rapid erosion of its diversity in the wild. Most beetroot breeding work is done in temperate countries, but some is also done in southern China and northern India. The traits breeders aim to incorporate include improvement in the speed of root formation, the limitation of leaf production, the production of homogeneous colour, good symmetrical shape and appearance, improved taste characteristics, and the prevention of bolting. Biotechnology Beta vulgaris was among the first crops to be modified by genetic engineering. Sugar beet has been modified to be resistant to herbicides, as previously noted. With world sugar production exceeding demand, there has been little incentive to modify sugar beet to increase yield. Herbicide-resistance makes weed control in sugar beet more efficient and reduces on-farm costs. There have been sound commercial reasons for concentrating on herbicide-resistance as a trait in transgenic crops. It helps, for instance, to preserve the market share for brand-name herbicides. Monsanto, for instance, have modified a range of crops to be resistant to glyphosate herbicide at a time when its Roundup glyphosate herbicide is coming out of patent. Roundup has been one of Monsanto's most profitable products over recent years. Farmers must sign a licensing agreement with Monsanto when growing the company's Roundup-Ready crops, in which they agree to spray only Roundup herbicide, and not generic glyphosate products, on these crops. New factories producing Roundup are springing up around the world, most notably in South America, to meet demand for increased Roundup spraying on Round-up soybeans, maize, cotton, oilseed rape and sugar beet. Although herbicide-resistant sugar beet is being grown successfully in the USA and other countries, its introduction into Europe has been delayed due to concerns that its cultivation will be detrimental to the environment. Countryside and agriculture are much more intrinsically linked in Europe than in North America. In an extensive three-year programme of farm-scale evaluations of transgenic crops in the UK, it was found that herbicide-resistant sugar beet was sprayed with more herbicide than conventional sugar beet, reducing weed biomass sixfold late in the season, with detrimental effects on biodiversity. Reductions in seed and insect food could have serious long-term effects on bee, butterfly and bird populations. In parts of Europe there is a move to see farmers not just as producers of food but also as custodians of the countryside; a view that acknowledges the economic importance of rural tourism. When growing a crop that is already overproduced, moves towards methods of cultivation that enable crop production and nature to co-exist need to be encouraged. The scorched earth, weed-free transgenic crop route is out of step with this way of thinking. Other concerns expressed about the cultivation of transgenic sugar beet include gene flow and the increased possibility that resistance will develop in weeds to herbicides. Transgenes could easily spread from transgenic sugar beet to other cultivated and wild Beta vulgaris plants, all of which readily interbreed. The exchange of genes between bolting sugar beet and weeds has been demonstrated in France, where hybrid weed beets are a significant weed problem. The acquisition of herbicide-resistance genes could make weed beet an even greater problem. The spread of herbicide-resistant transgenes from one sugar beet crop to another was first reported in Europe in 2000. The first wave of transgenic crops was primarily modified for herbicide-resistance. However, a wider range of modifications are now being made to crops. Sugar beet, for instance, is now being modified for resistance to the viral pathogen Beet Necrotic Yellow Vein Virus (BNYVV) and resistance to nematode pests. Transgenic sugar beet could soon be developed with a modified sugar content. Work in Europe, for instance, is underway to produce a range of sugar molecules called fructans in sugar beet roots. Novel fructans will be designed to meet a range of needs as functional foods or food ingredients, including low-calories sweeteners, dietary fibre or bulking agent in processed food. Fructans can also be used as raw materials in a wide range of non-food products such as biodegradable plastics, detergents and adhesives, and in cosmetics. Such modifications would effectively convert sugar beet into a new crop. Sugar beet farmers in Europe would benefit from diversification and increased markets, at a time of sugar overproduction and when their subsidies for growing sugar are being threatened by a World Trade Organization (WTO) ruling (May 2004). Beet may become an important crop in which to produce novel chemicals for industrial applications. Sugar beet has been put to a range of uses over the years. In addition to refined sucrose and sweet products, the tops and pulp have been used as animal fodder, the dried pulp has provided a coffee substitute, and its by-products have been used to manufacture industrial and pharmaceutical products. Its juice can be processed into a tough varnish with industrial applications, for example, while sugar beet is a source of citric acid. The cosmetics industry makes extensive use of citric acid, which is added to products to help them match the pH of the skin. Beet crops may become increasingly used in the production of biofuels. The technology for this is already in place. The gasohol that drives cars in Brazil, for example, is made using sugar cane. Using the same principle, sugar beet is one of the crops that can produce bioethanol in Europe. Mixtures of bioethanol and petrol are used to fuel cars in some European countries. Biotechnology is extending the industrial uses of sugar beet by-products. Beet pulp is a raw material used as a substrate for the culturing of bacteria. The ferulic acid naturally found in beet pulp, for example, can be converted into vanillin by a species of soil bacterium in the laboratory. Vanillin is the most important component of vanilla essence. A range of industrial products, including ethylene fuel and polyurethane foams could be produced from sugar beet with the aid of biotechnology. The techniques of tissue culture and genetic engineering developed for sugar beet are applicable to beetroot. Tissue culture involves the production of clonal regenerants from tissue taken from a plant; usually undifferentiated callus tissue from the cotyledon of a plant embryo. Regenerants grow into normal plants. They are easily screened in breeding programmes and are ideal for genetic manipulation. An additional advantage of large-scale tissue culture is that it gives rise to somaclonal variation or novel genetic material for plant breeders to exploit. Beetroot was included to a limited extent in early studies of regenerating Beta vulgaris in tissue culture, although most work has been done on sugar beet. Sabir and Ford-Lloyd included a fodder beet and four beetroot cultivars in their study of the mass production of regenerants in tissue culture (micropropagation). This study showed that all the tested forms of Beta vulgaris produced large numbers of regenerants under tissue culture conditions. Beetroot could be genetically engineered for herbicide-resistant or for resistance to viral pathogens in the same way as sugar beet. However, it is unlikely that such modifications can be justified in commercial terms. Modifications relating to colour or to root components having medicinal properties are more likely goals. Variations in beetroot pigments, specifically the betalains that give the roots their distinctive red colour, have been studied using clonal material obtained by tissue culture. Girod and Zryd demonstrated the importance of light, for instance, in the induction of betalain synthesis using beetroot cell cultures. It may soon be possible to manipulate betalain pigments in beetroot to influence root colour or to make the pigments more stable. This could be done to improve their value as a source of natural food colouring. However, beetroot is a rustic crop, on the fringes of agribusiness. It is not a natural designer crop. The market for beetroot is small compared to most of the crops that have been genetically modified. These crops have tended to be commodity crops that are heavily processed, whereas beetroot is usually just boiled and pickled when processed. Beetroot also has relatively few pest and disease problems, and is easy to cultivate organically without pesticides. The main problem that has beset beetroot growers over the years has been bolting or premature flowering. Conventional breeding methods have produced cultivars that are resistant to bolting, which can be grown early in the season. It is therefore unlikely that transgenic beetroot will ever be sold as a fresh vegetable. However, it is quick and easy to grow, and the methods to genetically engineer it have already been worked out using sugar beet. Therefore, in the future beetroot could be genetically modified to produce high-value products for use in the pharmaceutical and food industries. Bibliography for Chapter Four Allen, A. (2003) Saving seed from biennial veg, The Organic Way, 173: 22-23. Biggs, M., J. McVicar and B. Flowerdew (1997) The Complete Book of Vegetables, Herbs and Fruit. London: Kyle Cathie, pp. 38-42. Bosemark, N.O. (1993) Genetics and breeding, in: D.A. Cooke & A.K. Scott (eds.) The Sugar Beet Crop. London: Chapman and Hall, pp. 67-119. Castellane, P.D., D.E. Foltran, M.E. Ferreira and P.A. Bellingieri (1990) NPK fertilization of carrot (Daucus carota L.) and beetroot (Beta vulgaris L.) crops on soil of high fertility, Revista de Agricultura, Piracicaba, 65(3): 257-266. Chiji, H., S. Tanaka and M. Izawa (1980) Phenolic germination inhibitors in the seed balls of red beet, Agricultural Biological Chemistry, 44: 205-207. Coleman, S.M. (2004) 'Oriental wisdom', Seed News (HDRA), 41: 9-10. Cooke, D.A. (1993) Pests, in: D.A. Cooke & A.K. Scott (eds.) The Sugar Beet Crop. London: Chapman and Hall, pp. 429-483. Darwin, C. (1859) The Origin of Species. Harmondsworth: Penguin Classics, p. 357. Draycott, A.P. (1972) Sugar-beet Nutrition. Barking, UK: Applied Science Publishers. Duan, X., J.S. Burris (1997) Film coating impairs leaching of germination inhibitors in sugar beet seed, Crop Science, 37: 515-520. Duffus, J.E. and E.G. Ruppel (1993) Diseases, in: D.A. Cooke & A.K. Scott (eds.) The Sugar Beet Crop. London: Chapman and Hall, pp. 347-427. Girod, P.A. and J.P. Zryd (1987) Clonal variability and light induction of betalain synthesis in red beet cell cultures, Plant Cell Report, 6: 27-32. Hellyer, A. (1993) The Hellyer Pocket Guide. London: Hamlyn. HDRA (2003) Seed Saving Guidelines. Henry Doubleday Research Association, Ryton, UK. Hruschka, H.W. (1977) Postharvest weight loss and shrivel in five fruits and five vegetables, USDA-ARS Market Research Reports, 1059, 23pp. Kays, S.J. (1997) Postharvest Physiology of Perishable Plant Products. Athens, Georgia, USA: Exon Press, pp. 347, 356. Nottingham, S.F. (2002) Genescapes: The Ecology of Genetic Engineering. London: Zed Books. Philips, R. and M. Rix (1993) Vegetables. London: Pan, pp. 70-75. RHS (Brickell, C. ed.) (1992) Royal Horticultural Society Encyclopedia of Gardening. London: Dorling Kindersley. Sabir, A.A. and B.V. Ford-Lloyd (1991) Processing crop plant germplasm in vitro for mass production of regenerants: a case study with beet, Journal of Biotechnology, 17: 257-268. Salter P.J., J.K.A. Bleasdale et al.. (1979) Know and Grow Vegetables. Oxford, UK: Oxford University Press. Santos, D.S.B., and M.F.A. Pereira (1989) Restrictions of the tegument to the germination of the Beta vulgaris seeds, Seed Science and Technology, 17: 601-611. Smit, T. and P. McMillan Browse (2000) The Heligan Vegetable Bible. London: Cassell Illustrated. Strickland, S. (1998) Heritage Vegetables: The Gardener?s Guide to Cultivating Diversity. London: Gaia Books. Sudell, R. (ed.) (1935) The New Illustrated Gardening Encyclopaedia. London: Oldham Press, pp. 99-101. Taylor, A.G., M.C. Goffinet, S.A. Pikuz, T.A. Shelkovenko, M.D. Mitchell, K.M. Chandler and D.A. Hammer (2003) Physio-chemical factors influence beet (Beta vulgaris L.) seed germination, in: G. Nicolas K.J. Bradford, D. Come, and H.W. Pritchard (eds.) The Biology of Seeds: Recent Research Advances. Wallingford, UK: CABI Publishing, pp. 433-440. Thornton, N.C. (1933) Carbon dioxide storage. III. The influence of carbon dioxide on oxygen uptake by fruits and vegetables, Boyce Thompson Inst. Contrib., 5: 371-402. Whitney, E.D. (1989) Beta maritima as a source of powdery mildew resistance in sugar beet, Plant Disease, 73: 487-489.

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