Race distribution pattern of Magnaporthe oryzae causing rice blast in mid and high altitudes of North-Western Himalayan region of India

Rice blast pathogen can rapidly change in virulence, and may overcome resistance in popular rice cultivars resulting in severe outbreak of the disease. To understand virulence pattern in Magnaporthe oryzae populations, 16 blast affected samples were collected from hills of Uttarakhand state of India and tested on 26 monogenic differentials (MDs) of rice carrying blast resistance genes, Pi20, Pi19, Pi11(t), Pil2(t), Pi9, Pi7(t), Pi5(t), Pi3, Piz-5, Piz-t, Piz, Pita2-Re, Pita2-PI, Pita-CP1, Pita, Pit, Pish, Pi1, Pik-s, Pik-p, Pik-m, Pik-h, Pik, Pii, Pib,and Pia individually on near-isogenic lines of a Japonica type rice cutivar, “Lijiangxintuanheigu” (LTH) genetic background along with LTH as a blast susceptible (S) check, and VL Dhan 154 as a resistant (R) check. The virulence frequency varied in the range of 21–93%. The isolates from low hills showed low virulence frequency (29–39%) and the isolates from mid hills had low to moderate virulence frequency (21–64%) whereas high hilly zone showed moderate to high virulence frequency (57–93%). A total of 16 races were classified out of these isolates. Highly virulent isolate, classified as U43-i7-k177-z17-ta733 race and the LTH lines carrying most of the R-genes except Pib and Pish showed susceptible reaction to this race. An attempt was made to use the MD set and classify races to know their distribution pattern in Uttarakhand hills of the northwestern Indian Himalayan region. © 2023, Indian Phytopathological Society.