Identification of novel tan spot resistance loci beyond the known host-selective toxin insensitivity genes in wheat |
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Authors: | C-G Chu T L Friesen S S Xu J D Faris |
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Institution: | (1) Department of Plant Sciences, North Dakota State University, Fargo, ND 58105, USA;(2) USDA-ARS, Northern Crop Science Laboratory, 1307 18th Street North, Fargo, ND 58105-5677, USA |
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Abstract: | Tan spot, caused by Pyrenophora tritici-repentis, 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. None of these QTLs corresponded to known
host selective toxin (HST) insensitivity loci, but a second QTL on chromosome arm 5BL conferred resistance to the Ptr ToxA
producing isolates of races 1 and 2 and corresponded to the Tsn1 (Ptr ToxA sensitivity) locus. 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.
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