Genetic Variation of Rice Blast (Pyricularia oryzae) Isolates in Laos

The pathogenicity of 192 blast isolates collected from regions across the whole of Laos from 2007 to 2009 showed a wide variation in terms of the frequencies of virulence toward differential varieties (DVs) and the susceptible control cultivar Lijiangxintuanheigu. High frequencies of virulence (>50%) were found in the reactions of DVs for Pit, Pia, Pi3, Pi5(t), Pik-s, Piz-t, Pi19(t), and Pi20(t); intermediate values (from 10 to 50%) were found in DVs for Pib, Pii, Pik-m, Pi1, Pik-h, Pik, Pik-p, Pi7(t), Piz-5, Pita (two lines), Pita-2 (two lines), and Pi12(t); and low frequencies (