Genetic variation of Magnaporthe oryzae avirulence genes, AVR-PiK and morphological characterization of rice blast isolates in Thailand
C. JANTASURIYARAT (1), A. Longya (1), T. Sirisathaworn (1), C. Chaipanya (1) (1) Department of Genetics, Faculty of Science, Kasetsart University, Chatuchak, Bangkok 10900, Thailand, Thailand

Rice (Oryza sativa L.) is the most widely consumed staple crop, feeding more than half of the world’s population. To feed the still growing population, rice varieties with higher yield potential and greater yield stability are needed; however, biotic and abiotic stresses take a serious toll on rice production. Rice blast disease, caused by Magnaporthe oryzae, is among the most devastating disease that affects rice production worldwide. The resistant rice varieties obtained were unstable and became susceptible to the disease within a few years of release because the instability of avirulence gene (Avr) in blast fungus. The objective of this study was to analyze the fungal characteristics, spore morphology, spore germination rate and the genetic variation of effector genes, Avr genes in 60 rice blast fungus isolates from Thailand. The results revealed that Thai rice blast isolates were very diverse. We obtained 5 haplotypes of Avr-Pik gene including 4 previous identified haplotypes (Avr-PikA, C, D, and E) and one novel haplotype which named, AVR-PikF. The most frequent haplotype was Avr-PikD (50 of 60 isolates). Interestingly 28 out of 50 Avr-PikD isolates, contained two copies of Avr-PiK gene, which were Avr-pikD and the new allele, Avr-pikF. We validated the blast isolates with two copies of Avr-PiK gene using single spore isolation and Real-Time PCR method. This is a new and very interesting finding which may lead to the understanding in the mechanism and the evolution of the rice blast fungus to overcome the resistance in rice. 

Abstract Number: P9-265
Session Type: Poster