Chai Nat 72 Mungbeans

Chai Nat 72 Mungbeans

Mungbeans has been grown in Thailand for a long time. Up until 1998, the total planted area was found to be 2.75 million rais resulting in a total grain yield of 277 thousand tons. Most production is used for domestic consumption especially in the food industry such as for Mungbeans sprouts, Desserts, and vermicelli. However, the production appears not to be sufficient for the present and future use. This implies that it is necessary to increase the total grain yield to meet the in-country demand. One way to achieve the target is to improve varieties by increasing their resistance or tolerance to the stem borer [Ophiomyia phasioli (Tryon)], which is the major destructive pest of mungbeans.

Thus, Chai Nat Field Crops Research Centre, which is responsible for research and development on mungbeans, initiated a breeding program in 1987 which involves the use of mutation technique. About ten thousand seeds of mungbeans variety, Kampaeng Saen 2, were treated with 600 kilorads of gamma rays in 1987. M₁ seed were grown in the field and seeds from the particular plants were collected for further selection. That is, within each of the generations of M₂ – M₄ in 1987-1988, single seed from particular plants were kept. In 1989, the selection was done for the M₅ generation and only for the plant that had an erect growth habit with more than 12 pods/plant and large seed sizes. Twenty-six lines had been selected and used for the stem borer evaluation trial in early rainy season of 1989 and were grown under natural conditions. Results indicated that CNM 8709-5 showed moderate resistance to stem borer whereas the original variety, Kampaeng Saen 2, showed susceptibility (Table 1).

Table 1 Reaction of CNM 8709-5 to stem borer infestation and number of pupae per plant tested under
natural conditions in 1989 at Chiang Mai Field Crops Research Centre

Variety	Reaction to stem borer	Number of pupae per 10 plants
CNM 8709-5	Moderately Resistant		4.0 b
Chai Nat 36	Susceptible		8.5a
Kampaeng Saen 2	Susceptible		8.0a
CV(%)	-		23

CNM 8709-5 and others promising lines were further tested in yield trials in 6 regions involving 18 farm trials and 3 farm tests in a variety of environment conditions during 1992-1995. Data on yield can be summarized as shown in Table 2. CNM 8709-5 performed best in each of the seasons and also in the farmers’ fields when compared with the recommended variety, Chai Nat 36

Table 2 Overall mean grain yield of CNM 8709-5 and means within seasonal grouping including mean
for the station and farmers' fields from trials conducted between 1992-1995

Variety			grain yield (kg/rai)
	Overall	Dry	Rainy	Late rainy	Station	Farmer
	mean	season	season	Season		field
CNM 8709-5	1,325	1,387	2,220	1,169	1,312	1,325
Chai Nat .6	1,269	1,287	1,419	1,150	1,300	1,256

Results from the 1993 farm trials were used to study yield stability by looking at the regression coefficient and standard deviation. The analysis indicated that CNM 8709-5 showed greater stability in yield. Stem borer evaluation was observed again in 1995 and data (Table 3) also confirmed results from earlier trials.

Table 3 Reaction of CNM 8703-5 on stem borer infestation and number of pupae per 30 plants tested
under natural condition in late rainy season, 1995 at the farmer field, Chiang Mai province.

Variety	Reaction to stem borer	Number of pupae per 30 plants
CNM 8709-5	Moderately resistant		69.8 b
Chai Nat 36	Susceptible		85.0 a
CV(%)	-		7

On the basis of this data, CNM 8709-5 had been released and recommended to farmers. It is also registered with Department of Agriculture and named as Chai Nat 72.

Agronomic Traits
Trait			Chai Nat 72
Average grain yield (kg/rai)			1,325
1000 seed weight (g)			66
Number of pods/plant			15
Number of seeds/pod			11
Plant height (cm)			66
Days to the first flowering			32
Days to the first pod mature			50
days to harvest			63

Chai-nat72