Wheat leaf rust (Puccinia triticina) causes significant yield losses in wheat production worldwide. Genetic resistance is a cost-effective way to reduce these losses. Among the known leaf rust (Lr) resistance genes, nearly half are from alien sources. However, their deployment into wheat (Triticum aestivum L.) cultivars has been limited, likely because of fear of potential negative effects of linked alien genes. We report here the effects of the Lr47 introgression from Triticum speltoides on agronomic and quality traits in common wheat. Five pairs of hard red spring near-isogenic lines were tested in replicated field trials from 2002 to 2004. The presence of the Lr47 introgression was associated with an overall 3.8% reduction in grain yield (220 kg ha⁻¹), but it varied significantly across genotypes and environments. The Lr47 introgression also affected several quality parameters. Lines with the alien Lr47 segment showed consistent increases in grain and flour protein concentration (4 to 5 g kg⁻¹, P < 0.01) but also highly significant decreases in flour yield (21.8 g kg⁻¹, P < 0.001) and increases in flour ash (0.14 g kg⁻¹, P < 0.01). This information will help wheat breeders make informed decisions about the deployment of Lr47 in their breeding programs. An additional round of homeologous recombination will be necessary to determine if the detrimental effects on milling parameters are pleiotropic effects of Lr47 or the result of linked genes.

Several new races of the stripe rust pathogen have become frequent throughout the wheat growing regions of the United States since 2000. These new races are virulent to most of the wheat seedling resistance genes limiting the resistance sources that can be used to combat this pathogen. High-temperature adult-plant (HTAP) stripe rust resistance has proven to be more durable than seedling resistance due to its non-race-specific nature, but its use is limited by the lack of mapping information. We report here the identification of a new HTAP resistance gene from Triticum turgidum ssp. dicoccoides (DIC) designated as Yr36. Lines carrying this gene were susceptible to almost all the stripe rust pathogen races tested at the seedling stage but showed adult-plant resistance to the prevalent races in California when tested at high diurnal temperatures. Isogenic lines for this gene were developed by six backcross generations. Field tests in two locations showed increased levels of field resistance to stripe rust and increased yields in isogenic lines carrying the Yr36 gene compared to those without the gene. Recombinant substitution lines of chromosome 6B from DIC in the isogenic background of durum cv. Langdon were used to map the Yr36 gene on the short arm of chromosome 6B completely linked to Xbarc101, and within a 2-cM interval defined by PCR-based markers Xucw71 and Xbarc136. Flanking locus Xucw71 is also closely linked to the grain protein content locus Gpc-B1 (0.3-cM). Marker-assisted selection strategies are presented to improve stripe rust resistance and simultaneously select for high or low Gpc-B1 alleles.