Current status of mungbean and the use of mutation breeding in Thailand.

Seeds of mungbean varieties Khampang Saen 1 (KPS1) and Chai Nat 36 (CN36) were irradiated with a dose of 500Gy Gamma-rays and treated with 1% ethyl methane sulphonate. The objectives of this experiment were seed yield improvement and powdery mildew resistance. A number of mutant lines were selected from M 2 onwards. Three promising mutants, M4-2, M5-1 and M5-5, gave 8-11% and 2-5% higher mean yield than those of KPS1 and CN36, but showed similar disease infection to their original parents tested during 1997-2006. The objective of the second experiment was to improve mungbean variety tolerance to beanfly, a key pest of mungbean. Seeds of var Khampang Saen 2 (KPS2) were irradiated with 600Gy Gamma-rays. A mutant line was selected and subsequently officially released as Chai Nat 72 (CN72) in 2000. It is the first mungbean variety released and developed through mutation techniques in Thailand. CN72 had lower beanfly infestation than a susceptible variety, CN36. The result of an addition trial conducted on calcareous soil showed that grain yield of mutant CN72 was superior to that of KPS2. The third experiment of the Mungbean Mutant Multilocation trials was conducted in two sites during 2003-2005. All mutants retained most traits of the original varieties, including yield. The highest yielding mutant across all five trials was CN72 which was similar to its progenitor (KPS2) and the local check, CN36. These three entries bore large seeds (70 g per 1,000 seeds), which is a desirable trait for Thai and international markets. An exotic entry, native variety showed least incidence of powdery mildew disease. It will be used as a source of disease resistance in the breeding program.