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Oral: Fungal Pathogenicity


Genetics behind avirulence: identification of novel avr-genes in Magnaporthe oryzae
D. TATE (1), J. Hu (1), V. Ganeshan (1), T. Mitchell (1) (1) The Ohio State University, U.S.A.

Rice blast disease, caused by Magnaporthe oryzae, accounts for 10-30% of yearly rice loss which is estimated to represent enough food to feed 60 million people. The study of interactions between M. oryzae and rice can be used to help mitigate one of the most devastating diseases plaguing a primary food source and knowledge of this pathosystem can be used to manage related fungal diseases. The objective of this study is to find the corresponding avirulence (Avr)-gene to the Pi-2 resistance (R)-gene in hopes of better understanding the strong relationship between M. oryzae and rice. In previous studies we have identified five candidate AvrPi2 genes by Agrobacterium tumefaciens-mediated transformation; infection assays; and TAIL-PCR with the incompatible strain KJ201. These genes have been cloned into the compatible strain Chinos. By infecting Pi-2 R rice plants with the Chinos transformants, and assessing disease, we were able to identify and characterize the most probable cognate Avr-gene. Pathogenicity assays demonstrated that two transformed lines Chinos4842 and Chinos8832 produced a similar phenotype to KJ201, with Chinos4842 showing a nearly identical phenotype match. Further, the mutants’ ability to induce a hypersensitive response (HR) was assessed using 3,3′-diaminobenzidine (DAB) staining in leaf sheath assays. Of the transformed lines, Chinos4842 was the only line able to produce a HR. These results strongly suggest that MGG_04842 is AvrPi2.