Classification and diversity assessment of Pyricularia oryzae based on leaf and neck blast pathogenesis on Khao Dawk Mali 105

Abstract

Forty isolates of P. oryzae were obtained from disease outbreak areas in various regions of Thailand. The fungi were divided into two groups; group 1 included 2 isolates which cause only neck blast with disease score of 7 – 9 and group 2 included 23 isolates which cause leaf and neck blast symptoms with disease scores of 5 – 6 and 7 – 9, respectively. The two groups of fungi were tested on 31 NILs. The avirulence genes including Avr-Pik (Avr-Pik, Avr-Pikm, Avr-Pikp), Avr-Pi1, Avr-Pi3, Avr-Pi5(t), Avr-Pi7(t), Avr-Pi9, Avr-Pi20, Avr-Pii and Avr-Pita were found in both groups whereas Avr-Pi11, Avr-Pi12, Avr-Pi19, Avr-Pia, Avr-Pib, Avr-Pikh, Avr-Piks, Avr-Pish, Avr-Pita, Avr-Piz, Avr-Piz-5 and Avr-Piz-t were detected only in the group 2. The results explained the relationship between fungi and the avirulence genes functioned at different stages of rice.