Dynamic of Pyricularia oryzae at the two stages, leaf, and panicle neck blast based on the assessment of population structure at leaf, tiller, and field levels

In order to assess the dynamic of Pyricularia oryzae at leaf and panicle neck blast stages, population genetic structures of the 142 isolates were investigated in a rice field and at three levels using SSR markers and five primer pair combinations. All the isolates were collected from the two-leaf and panicle stages at three levels. In the first level, isolates collected from leaf and panicle neck blast stages in the rice field were analyzed. In the second level, isolates belonged to the leaf and panicle neck populations were collected from tillers of the same rice hill and analyzed. In the third level, the ienvestigated isolates belonged to three populations and were obtained from three distinct leaf spots from the same rice leaf in a rice tiller. Based on constructed dendrogram for all of the 142 isolates, genetic similarity varied from 89 to 100% among the isolates. Population genetic estimations at the three studied levels showed that the amount of gene flow was 57.62, 10.68, and 4.783, respectively between the isolates. Detection of mating type idiomorphs of the studied isolates using multiplex PCR showed that all the isolates had Mat1-1 idiomorph. This indicates the absence of sexual reproduction within the M. oryzae populations in rice fields in Guilan province and the fungus reproduces only in an asexual way. Low genetic variation and high genetic similarity among the populations of the causal agent of rice blast disease in Guilan province confirm this result.