Rice blast, caused by Pyricularia grisea, is one of the major diseases affecting rice yields in Thailand. We are analyzing the virulence spectrum and genetic structure of the Thai blast pathogen ...population. In this study, we present results for 29 isolates collected from different rice-growing regions in Thailand. Genetic diversity was assessed by random amplified polymorphic DNA (RAPD) analysis and virulence patterns were determined by spray-inoculating more than 50 rice cultivars carrying different resistance genes, including Thai rice cultivars, with each isolate. Cluster analysis of molecular band profiles grouped the isolates in five groups sharing 80% or a higher percentage of band similarity. The isolates showed a diversity of (a)virulence patterns, and only two of the isolates tested showed an identical pattern. We conclude that there is a high degree of pathotype diversity among Thai isolates of the rice blast pathogen. Resistant reactions were more common than susceptible reactions to each of the individual isolates. There was no clear overall agreement between the molecular profile of isolates and their virulence pattern. However, a few cultivars showed RAPD group-specific (a)virulence.
Blast disease, caused by Pyricularia grisea, is one of the most serious diseases of rice in Thailand. To study the diversity in this fungus, rice samples showing blast symptoms on the leaf, neck, ...collar, panicle, and seed were collected from rice fields in various locations in Thailand. During the collection, it was observed that the popular cultivars grown by farmers, KDML105 and sticky rice, had high disease severity, especially in northern and northeastern Thailand. Several cultivars, such as Hom Klong Laung and Hom Suphan, were highly resistant in some locations byt susceptible in others. In addition to differences in cultural characteristics of Pyricularia grisea between isolates, we found high diversity in spore morphology among isolates from different locations. Moreover, results of the pathotype test indicated that many isolates were compatible with different cultivars. When examined for mating type, results showed 123 blast isolates of type I and 21 of type II.
One of the major constraints to Thai rice cultivation is blast disease, especially in aromatic rice Khao Dawk Mali 105. Rice is susceptible to blast disease at many growth stages. The genetic ...diversity of blast isolates was analyzed by DNA fingerprinting using a molecular technique. We collected samples and produced about 1,000 monospore isolates from rice cultivars, barley, and weeds, which covered rice fields in Thailand. We screened mating type and fertile isolates from testers with two fertile isolates from barley in the country and found mating types II and I from blast isolates. Barley isolates were clearly distinct from rice isolates using the AFLP technique. The occurrence of the opposite mating type is one reason for the high defree of genetic diversity of blast pathogen populations in Thailand. The DNA pattern of blast isolates was clustered in each group at 85% similarity. Some blast isolates represented each cluster group that was investigated for its virulence pattern on the rice differential host set, including Japanese differential cultivars, near-isogenic lines, some cultivars that carry known resistance genes, and traditional Thai cultivars. The pathotype test specifically aimed at detecting virulence gene characteristics that are lineage-specific. Based on data, the pathogen population in an area is expected to adapt to the host population. These cultivars should be used efficiently for suitable differential host set that involves interaction between the host and blast pathogen in Thailand. The data should be useful for developing rice cultivars with a more durable resistance to blast disease in Thailand.
Fertility and mating type of Magnaporthe grisea rice pathogen in Thailand Saengchai Sriprakhon(National Science and Technology Development Agency, Bangkok (Thailand). National Center for Genetic Engineering and Biotechnology); Eduard Roumen(Jozef Plateaustraat 22, Gent (Belgium). Aventis CropScience); Arunee Surin(Pension official of Department of Agriculture, Bangkok (Thailand)) ...
2001
Conference Proceeding
