One hundred and twenty-nine monoconidial isolates of Pyricularia grisea from rice were collected in Vietnam, mainly in the Mekong River Delta (MRD), in 1995-1996 to characterize their virulence. These isolates were classified into 12 pathogenic groups (races) based on their virulence to 12 Japanese differential rice varieties (modified Kiyosawa's differentials). Race 002.4 was predominant and was found in 10 provinces of MRD, followed by races 106.4, 006.4, 102.4 and 002.0. Differential varieties Aichi Asahi (which carries resistance gene Pia) and K59 (Pit) were susceptible to 93.8% and 86

No abstract