Population structure of Pyricularia grisea in two IRRI blast nurseries: implications and applications
1996
Chen, D.H. | Zeigler, R.S. | Nelson, R.J.
Population structure of Pyricularia grisea was analyzed at two field sites used by IRRI for evaluating blast resistance in rice. During 1992, 1,516 monoconidial isolates of the pathogen were collected from 38 rice cultivars and lines from the blast nursery of the International Rice Research Institute (IRRI-BN) and from the upland screening site at Cavinti, Laguna, Philippines. Each isolate was subjected to DNA fingerprinting and phenetic analysis using the probe MGR586. Nine lineages, or groups of isolates sharing 80% DNA similarity and inferred to be related by descent, were detected at Cavinti, while four lineages were found at the IRRI-BN. Inoculation studies were conducted to more thoroughly define the resistance spectra of selected rice genotypes. A characteristic virulence spectrum could be discerned for each pathogen lineage, and a characteristic resistance spectrum could be discerned for each host genotype. An experiment on line and cultivar mixtures was conducted at Cavinti in 1994. "Good" line/cultivar mixtures (those with components having complementary resistance spectra to the known line/cultivar such that no line/cultivar could infect all components) and "poor" line/cultivar mixtures (those for which one or more line(s)/cultivar(s) could infect all the mixture components) were designed for CO 39 near-isogenic lines and rice cultivars. Leaf blast severity (diseased leaf area, or %DLA) was reduced for the good line mixture relative to the mean of the mixture components, but not for the poor line mixture. For the cultivar mixtures, both good and poor mixtures showed significantly reduced %DLA in later plant growth stages. These results suggest that knowledge of pathogen population structure can be useful for making decisions both for breeding and gene deployment
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