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Oral: Fungal Pathogenicity


Molecular dissection of a complex gene locus conferring high virulence on barley cv. Bowman in the fungal cereal pathogen Cochliobolus sativus
S. ZHONG (1), Y. Leng (1) (1) North Dakota State University, U.S.A.

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Cochliobolus sativus (Anamorph: Bipolaris sorokiniana) is a fungal pathogen causing spot blotch, common root rot, and black point in cereal crops. For spot blotch, four pathotypes (0, 1, 2 and 7) have been identified based on their differential virulence patterns on three barley genotypes (Bowman, ND5883 and NDB112), but the molecular mechanism underlying host specificity of these pathotypes is not well understood. Our previous studies indicated that isolate ND90Pr (pathotype 2) has a complex gene locus (VHv1) conferring high virulence on barley cv. Bowman. VHv1 is located in an ND90Pr-specific genomic region, which contains 43 predicted genes including two for nonribosomal peptide synthetases (NRPSs). Knocking out either of the two NRPS genes led to loss of high virulence on cv. Bowman, suggesting that both NRPSs are involved in the biosynthesis of a presumably secondary metabolite virulence factor in the pathogen. We further characterized other genes adjacent and between the two NRPS genes at the VHv1 locus and found that the two genes encoding 3-hydroxyacyl-CoA dehydrogenase and short-chain dehydrogenase/reductase (SDR), respectively, were also required for the high virulence of isolate ND90Pr on barley cv. Bowman.