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Evidence of Genetic Exchange by Parasexual Recombination and Genetic Analysis of Pathogenicity and Mating Type of Parasexual Recombinants in Rice Blast Fungus, Magnaporthe oryzae

July 2006 , Volume 96 , Number  7
Pages  746 - 750

M. T. Noguchi , N. Yasuda , and Y. Fujita

First author: National Agricultural Research Center, Hokuriku Area, 1-2-1 Inada, Joetsu, 943-0193, Japan; and second and third authors: National Agricultural Research Center, Tsukuba 305-8666, Japan

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Accepted for publication 23 February 2006.

A selectable marker gene conferring resistance to bialaphos (BI) was introduced into rice blast isolate Y90-71BI and another conferring resistance to blasticidin S (BS) into isolate 3514-R-2BS of Magnaporthe oryzae to demonstrate exchange of DNA. Colonies obtained from co-cultures of these two isolates were resistant to both BI and BS and had both resistance genes as shown by Southern blot analysis of their genomic DNA. Conidia from these BI-BS-resistant isolates had only one nucleus per cell after staining with 4′,6-diamidino-2-phenylindole (DAPI). Using flow cytometry, however, these BI-BS-resistant isolates were found to be haploid. Segregation of BI-BS-resistant isolates for pathogenicity (avirulence to virulence) on rice line K59-1 was consistent with a 1:1 ratio, as was segregation for mating type. These BI-BS-resistant isolates were thus apparently derived from parasexual exchange of DNA and the segregation of pathogenicity and of mating type of the parasexual recombinants might correspond to that of the progeny of the offspring of the sexual cross.

Additional keywords: anastomosis, heterokaryosis, Oryza sativa .

© 2006 The American Phytopathological Society