Sources of Leaf Rust Resistance In Durum Wheat.

Leaf rust (Puccinia triticina) has caused major economic losses in durum wheat (Triticum turgidum L. subsp. durum (Desf.) Husn.) production in the recent years. Leaf rust race BBG/BN and its variants in Mexico are virulent on most commonly grown durum cultivars grown in Mexico, the United States and Canada. The BBG/BN rust epidemic on durum wheat during 2001-2003 resulted in estimated losses of about US$32 million to Mexican farmers. The BBG/BN race has begun to spread into the southwestern U.S., and it is a concern that it will move into the central North American rust corridor. All Canadian durum cultivars are susceptible to race BBG/BN and its variant BBG/BP.  This project was initiated to understand the genetics of resistance in the durum wheat genotype Sachem and Triticum turgidum subsp. carthlicum (Nevski in Kom.) Á.Löve & D.Löve genotype Blackbird, and to identify the leaf rust (Lr) genes and associated molecular markers. Eighty-nine doubled haploid (DH) lines from Sachem x Strongfield were genotyped with 426 simple sequence repeat (SSR) markers. Seventy-one DH lines from Blackbird x Strongfield population were genotyped with DArT markers and 257 unique DArT markers were used for genetic mapping. Strongfield is susceptible to BBG/BN and BBG/BP. Parents and doubled haploid lines were phenotyped in three distinct field leaf rust nurseries at Mexico, and greenhouse evaluation was done using races BBG/BN and BBG/BP. Data analyses were done using SAS v9 and QTL mapping softwares. Sachem showed a resistant reaction in field and indoor screening, while Blackbird had a moderately resistant reaction. Results suggest that Blackbird carries gene Lr16 while Sachem carries Lr14a and another minor gene. These leaf rust resistance sources provide additional breeding options to durum breeding programs.