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Magnaporthe grisea Pathogenicity Genes Obtained Through Insertional Mutagenesis

May 1998 , Volume 11 , Number  5
Pages  404 - 412

James A. Sweigard , 1 Anne M. Carroll , 1 Leonard Farrall , 2 Forrest G. Chumley , 3 and Barbara Valent 2

1Central Research and Development Department, and 2DuPont Agricultural Products, E. I. du Pont de Nemours and Co., Inc., P.O. Box 80402, Wilmington, DE 19880-0402 U.S.A.; and 3DuPont Agricultural Products, Barley Mill Plaza, P.O. Box 80037 Wilmington, DE 19880-0037 U.S.A.

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Accepted 1 February 1998.

We have initiated a mutational analysis of pathogenicity in the rice blast fungus, Magnaporthe grisea, in which hygromycin-resistant transformants, most generated by restriction enzyme-mediated integration (REMI), were screened for the ability to infect plants. A rapid primary infection assay facilitated screening of 5,538 transformants. Twenty-seven mutants were obtained that showed a reproducible pathogenicity defect, and 18 of these contained mutations that cosegregated with the hygromycin resistance marker. Analysis of eight mutants has resulted in the cloning of seven PTH genes that play a role in pathogenicity on barley, weeping lovegrass, and rice. Two independent mutants identified the same gene, PTH2, suggesting nonrandom insertion of the transforming DNA. These first 7 cloned PTH genes are described.

© 1998 The American Phytopathological Society