Study of Disinfecting Methods against Macrophomina sp. Infected on sesame Seed
Naruatai Worasatit1, Pornpan Suddhiyam1 and Siripong Kumpai2
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/ Ubon Ratchathani field crops research centre, P.O. Box69, Muang, Ubon Ratchathani 34000, Thailand. E-mail: ubfcrc@yahoo.com2/ Plant pathology and microbiology Division, Department of Agriculture, Chatuchak, Bangkok 10900, Thailand
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Charcoal rot of sesame caused by the fungus Macrophomina phasiolina, is one of the major diseases spreading throughout sesame growing areas. Sesame plants infected with this fungus show a brown lesion on the root or stem together with a discoloration on the leaves, followed by the plant eventually wilting and finally die. Seed transmission is an important means for the spread of the disease to new growing areas resulting in more crop loss (Sanaomung and Sirithorn,1996).
To solve this problem, different methods of disinfecting for the Macrophomina sp. Infected on sesame seed were studied at Ubon Rachathani Field Crops Research Center during 1995-1996. The four sesame varieties used were the white seeded “Roi Et 1” and “Maha Sarakham 60” the brown seeded “Ubon Ratchathani 1” and the local black seeded “Nakhon Sawan”. Seed were randomly selected and treated using physical and chemical procedures.
The two physical seed treatment were 1) soaking seed in warm water at 50OC for 30 min, and 2) oven drying seed at 55oC for 20 min. The chemical seed treatments were four fungicides (Benomyl, PCNB, Captan, and Carboxin). Seed were dusted by each of the fungicides at a rate of 2.5 g/kg of seed. A further chemical treatment was that of soaking seed in 2% NaOCl solution for 5 min. All treated seeds were placed on moistened paper to check for any infection from Macrophomina sp. Compared to untreated seed.
The result showed that Captan and Benomyl were the best disinfectants. Seed treated with these fungicides had Macrophomina infection at 0.1 and 0.6%, respectively, whereas the percentage of infection on untreated seed was 7.9%. White sesame seed was found to have more infection than that for the brown and black seed. Percentage of Macrophomina infection on seed of sesame variety Roi Et 1, Maha Sarakham 60, Ubon Ratchathani 1 and Nakhon Sawan were 5.6, 7.2, 2.4, and 0.9%, respectively.
Reference
Sanaomung, N., and Sirithorn, P. 1996. A summary research on sesame diseases at Khon Kaen University during 1986-1996. In Sesame. P.101-110. Ubonkit Opset Press, Ubon Ratchathani (in Thai).
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