Quantitative trait loci for resistance in wheat (Triticum aestivum) to Ustilago tritici

Loose smut [Ustilago tritici (Pers) Rostr.] of wheat (Triticum aestivum L) causes losses in grain yield roughly proportional to the incidence of the disease. Efforts to control this disease utilizing genetic resistance are being made in breeding programmes around the world. DNA markers for genetic resistance would greatly enhance breeding efforts by reducing the substantial time and labour resources necessary to screen for resistant lines using traditional inoculation methods. The objective of this study was to identify DNA markers associated with resistance. Doubled haploid progeny from the four crosses 'Glenlea'/'AC Taber', 'SC8021V2'/'AC Karma', 'Diamant'/TD12A, and 9340-CP*/'AC Vista' were evaluated with individual races of U. tritici and simple sequence repeat markers. Simple interval mapping was performed using MQTL software and single point analysis. 'Glenlea', which has complete and broad resistance to all known races of U. tritici in Canada, contributed a QTL for resistance to races T2, T10, T15, T19 and T39 at Xwmc160 on chromosome 5B. 'Glenlea' also contributed QTL for resistance to races T2, T9 and T15 at Xgwm302 on chromosome 7B and to races T9, T19 and T39 on chromosome 3A at marker Xwmc559. The chromosome 5B QTL from 'Glenlea' coincided with a race T39 resistance locus from 'AC Karma'. The 7B QTL from 'Glenlea' coincided with resistance to race T9 from 9340-CP* and T2, T9 and T27 resistance from TD12A. The QTL on 3A from 'Glenlea' was coincidental with T9 resistance from 9340-CP*. When evaluated with race T10, a QTL was identified near Xbarc183 on chromosome 6D from 'SC8021V2'. A QTL to race T9 from 'SC8021V2' within the interval Xcfa2019 to Xgwm344a was identified on 7A. A third QTL from 'SC8021V2' was located on 6B at Xbarc223 and Xbarc332b. The chromosome 5B locus together with either the 7A or 7B genetic loci would provide resistance to predominant races of loose smut found on the Canadian prairies.