Assessment of Genetic Diversity in Thai Isolates of Pyricularia grisea by Random Amplification of Polymorphic DNA

One hundred and seventy-four isolates of Pyricularia grisea were collected from various hosts such as barley, rice, weed and wild rice in Thailand. Seven arbitrary decamer primers from the set of University of British Columbia were employed and nine lineages were classified. Lineages B, C and H were predominant, contributing up to 70% of total pathogens in this study. Analysis showed that the distribution of each lineage differs from the predominant lineages across Thailand in such that other lineages were restricted in particular area. For instance, lineage A was limited only in southern Thailand, whereas wide distribution of lineages B and C reflected an influence of both biological and physical effects on pathogen variation. Principal component analysis resulted in a total of four groups of blast pathogen with small distinctions between barley-, rice-, weed- and wild rice-infected blast. Bridging relationships occurred among border isolates of weed and rice blast suggesting a chance of migrations between hosts. Higher diversity was observed in northern, north-eastern and central Thailand while eastern and southern parts were rather low. Genetic diversity indices elucidated an abundance of pathogen lineages existing in northern Thailand suggesting that it should be the centre of diversity