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Asian Journal of Agriculture and Development (AJAD) - Call for papers!

Genetic characterization of blast disease resistance on rice (Oryza sativa L.) varieties from Laos

(Lao PDR), Master of Science in Agronomy (Kasetsart University)

Thesis Abstract:

Rice blast disease, caused by Pyricularia oryzae, is one of the most devastating diseases of rice worldwide including Laos. The feasible control for rice blast is the use of resistant cultivars. The objectives of this study were to evaluate the reaction of 36 rice varieties to blast and to genetically characterize the blast pathogen. Twentyeight isolates of P. oryzae were collected from three different rice areas in Luang Prabang Province, Laos, and eight selected isolates of P. oryzae from Thailand. Single conidium isolates were inoculated into 36 commercial rice varieties. The rice varieties TDH21-B-24, JHN, and IR81431 cultivars had shown a high level of resistance against isolates from Laos and Thailand. When parents were screened against 28 isolates, it was found that TDK21 was resistant to isolates with its RI value of 0.81. Clustering of 36 blast isolates using 36 cultivars had shown pathotypic similarity index of 40 percent. In virulence testing of 36 blast isolates against the 36 tests varieties, 14 isolates were virulent (39%) and 22 (61%) were avirulent. The genetics of resistance to blast (TDK21) donor was crossed with TDK5 susceptible. The F1 seedlings of the cross between TDK5 with TDK21, the most susceptible resistant checks, in the LPB3-2 isolate Laos was resistant, indicating dominance of resistance over susceptibility. In the F2 population, the ratio of resistant and susceptible seedling in the cross of TDK5 × TDK21 showed goodness of fit to the expected ratio 3R:1S (X2-0.04, P = 0.90–0.80). In this research, the studied population and five resistant cultivars might be of interest to breeders from Laos.