Determination of Pathotype Diversity of Rice Blast Fungal Population in Thailand
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Abstract
Rice blast disease is the major disease in rainfed lowland area of Thailand. The causal fungus of this disease is Pyricularia grisea Sacc. Variation of this fungus was higher than other rice pathogens. This report used near isogenic lines (NILS) to detect the variation, pathothype and virulence spectrum of the fungus in Thailand during 2002-2005. Trap blast nurseries consisted of 9 Thai local cultivars and 18 NILs were conducted at Ubon Ratchathani Rice Research Center, Khon Kaen Rice Research Center, Phrae Rice Research Center, Phitsanulok Rice Research Center, and Phatthalung Rice Research Center. Single conidia was isolated from infected rice leaves. Virulence spectrum of blast populations were screened on 18 NILs. Two thousand four hundred seventy six isolates were classified into 623 pathotypes that could be devided into two groups; 145 common pathotypes and 340 rare pathotypes diversity index of blast population was high (0.83). Common pathotypes had virulence spectrum less than rare pathotypes. Site-specific and season-specific pathogen populations were found in this study. High pathogen diversity was found at Ubon Ratchathani Rice Research Center. Some resistant genes had potential to prevent infection from some pathotypes. However, many pathotypes could be compatible with a single resistant gene. The resistant genes Pi 1 group (Pi 1, Pi 1(t)LAC, Pi 1(t)TTP, Pi 1CL), Pi k group (Pi k, Pi kp, Pi kh) Pi ta2, Pi 5 and Pi 9 were effective resistance against many pathotypes. Combinations of resistant genes Pi 1 - Pi 9 and Pi ta2 - Pi 1CL were the most effective resistant gene pairs against blast populations in Thailand. This finding can be implemented in breeding for blast resistance in the Thai breeding program.
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References
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