IDENTIFICATION OF RICE BLAST RESISTANCE GENES IN SOUTH CENTRAL COAST OF VIETNAM USING MONOGENIC LINES UNDER FIELD CONDITION AND PATHOGENICITY ASSAYS

Blast caused by the fungus Pyricularia oryzae is a serious disease of rice (Oryza sativa L.) in Center of Vietnam, where temperate Indica rice is primarily grown. One method to overcome this disease is to develop disease resistant cultivars. Due to the genetic plasticity in the pathogen genome, there is a continuous threat to the effectiveness of the developed cultivars. Determination the blast resistance genes that are effective against strains of P. oryzae as well as population of the rice blast fungus in rice production areas for breeding programs. In the present study, we studied the interaction between 26 monogenic lines carrying at least one major R gene Pia, Pii, Pik-s, Pik, Pik-p, Pik-h, Piz, Pi2(t), Piz-t, Pi4(t), Pib, Pit, Pish, Pi1, Pi3, Pi5(t), Pi7(t), Pi9, Pi12(t), Pi19, Pik-m, Pi20, Pita2, Pita, Pi11(t) and Piz5 with local blast isolates under field conditions and greenhouse conditions. The result in the field conditions showed that Area Under Disease Progress Curves of monogenic lines was found ranging from 0 to 160. LTH was susceptible in all of regions. The monogenic lines carrying Pik, Pik-p, Pik-h, Piz, Pi1, Pi7 (t), Pik-m, Pi4(t), Pish, Pi9(t) and Pita were highly resistant to blast in both two season (2014 and 2015) and at all sites. In greenhouse conditions, the percentage of virulent reactions of monogenic lines to 40 isolates with valuers ranging from 19.4% to 71.0%. LTH was susceptible to all 40 isolates. All 26 monogenic lines were resistant to at least 9 isolates of P. oryzae and the frequency of resistant reactions of the monogenic lines carrying Pik, Pik-p, Pik-h, Piz, Pi4(t), Pi1, Pi7(t), Pi9, Pik-m and Pita were 92.5%, 95%, 95%, 95%, 77.5%, 97.5%, 95%, 95% and 82.5% respectively. These findings suggest that Pik, Pik-h, Piz, Pi4, Pi1, Pi7(t), Pi9, Pik-m and Pita may be important R genes for preventing blast disease in center of Vietnam. Based on these data, a useful strategy for managing rice blast disease by stacking pyramiding blast R genes against pathogenic P. oryzae isolates at hotspot in the Centre of Vietnam was proposed