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ARS Home » Plains Area » Fargo, North Dakota » Edward T. Schafer Agricultural Research Center » Cereal Crops Research » Research » Publications at this Location » Publication #220375
Title: Identification of novel tan spot resistance loci beyond the known host-selective toxin insensitivity genes in wheat

Author
item CHU, CHENGGEN - NORTH DAKOTA STATE UNIV.
item Friesen, Timothy
item Xu, Steven
item Faris, Justin

Submitted to: Theoretical and Applied Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/9/2008
Publication Date: 6/25/2008
Citation: Chu, C., Friesen, T.L., Xu, S.S., Faris, J.D. 2008. Identification of novel tan spot resistance loci beyond the known host-selective toxin insensitivity genes in wheat. Theoretical and Applied Genetics 117:873-881

Interpretive Summary: Tan spot is a destructive foliar disease of wheat and causes significant yield reduction in major wheat growing areas throughout the world. The objective of this study was to identify chromosomal regions, or quantitative trait loci (QTL), conferring resistance to tan spot in the wheat line TA4152-60. A mapping population derived from TA4152-60 ' ND495 was evaluated for reaction to tan spot using four virulent North American races of the fungus. Analysis revealed a total of five genomic regions significantly associated with tan spot resistance. Three of the QTLs were novel, two of which conferred resistance to all isolates tested and the third conferred resistance to three of the four races. The fourth QTL was specific to a single race and the fifth coincided with the known chromosomal location of the Tsn1 gene, which govern sensitivity to Ptr ToxA, a necrosis-inducing toxin produced by two of the races. These results indicate that the wheat-tan spot system is much more complex than previously thought and that selecting for toxin insensitivity alone will not necessarily lead to tan spot resistance. The markers identified in this work will be useful for introgressing the chromosomal regions containing novel resistance genes into adapted germplasm.

Technical Abstract: Tan spot, caused by Pyrenophora tritici-repentis (Died.) Drechs., is a destructive foliar disease of wheat causing significant yield reduction in major wheat growing areas throughout the world. The objective of this study was to identify quantitative trait loci (QTL) conferring resistance to tan spot in the synthetic hexaploid wheat (SHW) line TA4152-60. A doubled haploid (DH) mapping population derived from TA4152-60 ' ND495 was inoculated with conidia produced by isolates of each of four virulent races of P. tritici-repentis found in North America. QTL analysis revealed a total of five genomic regions significantly associated with tan spot resistance, all of which were contributed by the SHW line. Among them, two novel QTLs located on chromosome arms 2AS and 5BL conferred resistance to all isolates tested. Another novel QTL on chromosome arm 5AL conferred resistance to isolates of races 1, 2 and 5, and a QTL specific to a race 3 isolate was detected on chromosome arm 4AL. Only the QTL on chromosome arm 5BL conferring resistance to the Ptr ToxA producing isolates of races 1 and 2 corresponded to the Tsn1 (Ptr ToxA sensitivity) locus. The remaining four QTLs were not associated with any known host selective toxin (HST) insensitivity loci. This indicates that the wheat-P. tritici-repentis pathosystem is much more complex than previously thought and that selecting for toxin insensitivity alone will not necessarily lead to tan spot resistance. The markers associated with the QTLs identified in this work will be useful for deploying the SHW line as a tan spot resistance source in wheat breeding.