Tuesday, November 14, 2006

Genetic Analysis of Resistance to Fungal Inoculation and Toxin Infiltration of Pyrenophora tritici-repentis, Race 5 in a Hexaploid Wheat Population.

Pawan Singh, North Dakota State Univ, Loftsgard Hall, P.O. Box 5051, Fargo, ND 58105 and Mohamed Mergoum, Plant Sciences Dept, CIMMYT, North Dakota State Univ, Loftsgard Hall PO Box 5051, Fargo, ND 58105-5051.

Tan spot, a major foliar disease of wheat, is caused by an ascomycete Pyrenophora tritici-repentis. There are presently eight races of P. tritici-repentis. Race 5 isolates produce the host-specific toxin Ptr ToxB. Both the toxin and spore inoculation induce extensive chlorosis in hexaploid wheat. The objectives of this study are to determine the genetic control of resistance/insensitivity to spore inoculation and culture filtrate in a hexaploid wheat population. A mapping population of recombinant-inbred lines (RIL) was developed from a cross between the resistant line ND-735 and the susceptible cultivar Steele-ND. Plants were inoculated at the two-leaf stage and disease reaction was assessed eight days after inoculation based on lesion type. Genetic analysis of the RIL population indicates that single gene control resistance to extensive chlorosis induced by spore inoculation. Presently infiltration of the toxin Ptr ToxB in this population is in progress. Further genetic analysis and possible mapping of the resistance gene(s) would be conducted.