ARS | Publication request: Identification of Novel Tan Spot Resistance QTLs Using an SSR-Based Linkage Map of Tetraploid Wheat

Submitted to: Molecular Breeding
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 30, 2009
Publication Date: September 17, 2009
Repository URL: http://hdl.handle.net/10113/42090
Citation: Chu, C., Chao, S., Friesen, T.L., Faris, J.D., Zhong, S., Xu, S.S. 2009.Novel Tan Spot Resistance QTLs Detected Using an SSR-Based Linkage Map of Tetraploid Wheat. Molecular Breeding. 25:327-338.

Interpretive Summary: Whole genome genetic maps are powerful tools for the identification of important genes and provide useful information for crop improvement. Although great efforts have been taken on the construction of whole genome genetic maps in hexaploid bread wheat, very little efforts have been placed on whole genome mapping in durum wheat, Thus, durum wheat has very limited number of whole genome maps although it is an important cereal specifically used for making pasta products. In order to facilitate the genetic and genomic studies of durum wheat, we developed a tetraploid wheat doubled haploid (DH) population comprising of 146 lines derived from the cross between a durum wheat cultivar ‘Lebsock’ and a Persian wheat accession PI 94749. We used this DH population to construct whole genetic maps of all 14 chromosomes with 280 molecular markers. The DH population and the whole genome maps were then used to identify the genes associated with resistance to tan spot, a serious foliar disease of wheat. By elaborate genetic analysis and evaluation of the DH population for tan spot resistance, we detected five major genes controlling the resistance to two races of tan spot fungus. The DH population and genetic maps reported here will be useful for genetic dissection of important agronomic traits as well as the identification and development of markers for marker-assisted selection.

Technical Abstract: Durum wheat (Triticum turgidum L. subsp. durum, 2n = 4x = 28, AABB) is an important cereal used for making pasta products. Whole genome genetic maps are powerful tools for the identification of important genes and provide useful information for crop improvement. In this research, a tetraploid wheat doubled haploid (DH) population derived from the cross between the durum wheat cultivar ‘Lebsock’ and the T. turgidum subsp. carthlicum (2n = 4x = 28, AABB) accession PI 94749 was developed. The population consisted of 146 lines and was used to construct linkage maps of all 14 chromosomes. The maps consisted of 280 SSR markers and spanned 2,034.1 cM with an average density of one marker per 7.2 cM. The DH population and the whole genome linkage maps were then used to identify QTLs associated with tan spot resistance. The DH population was inoculated separately with two Ptr ToxA-producing isolates (Pti2 and 86-124) representing races 1 and 2, respectively, of Pyrenophora tritici-repentis, and five resistance QTLs were detected on chromosome arms 3AS, 3BL, 5AL and 7BL. Together, the QTLs explained a total of 46% and 41% of the phenotypic variation for reaction to Pti2 and 86-124, respectively. The Tsn1-Ptr ToxA interaction was not a significant factor in tan spot development in this population, and none of the QTLs corresponded to previously identified loci known to confer insensitivity to host-selective toxins (HSTs) produced by P. tritici-repentis. This result, together with those of other similar studies, indicates that the wheat-P. tritici-repentis pathosystem involves more factors than currently published host-toxin interactions. The DH population and genetic maps reported here will be useful for genetic dissection of important agronomic traits as well as the identification and development of markers for marker-assisted selection (MAS).