Grain protein content (GPC) is an important factor in pasta and breadmaking quality, and in human nutrition. It is also an important trait for wheat growers because premium prices are frequently paid for wheat with high GPC. A promising source for alleles to increase GPC was detected on chromosome 6B of Triticum turgidum var. dicoccoides accession FA-15-3 (DIC). Two previous quantitative trait locus (QTL) studies found that the positive effect of DIC-6B was associated to a single locus located between the centromere and the Nor-B2 locus on the short arm of chromosome 6B. Microsatellite markers Xgwm508 and Xgwm193 flanking the QTL region were used in this study to develop 20 new homozygous recombinant substitution lines (RSLs) with crossovers between these markers. These 20 RSLs, plus nine RSLs developed in previous studies were characterized with four new RFLP markers located within this chromosome segment. Grain protein content was determined in three field experiments organized as randomized complete block designs with ten replications each. The QTL peaks for protein content were located in the central region of a 2.7-cM interval between RFLP markers Xcdo365 and Xucw67 in the three experiments. Statistical analyses showed that almost all lines could be classified unequivocally within low-and high-protein groups, facilitating the mapping of this trait as a single Mendelian locus designated Gpc-6B1. The Gpc-6B1 locus was mapped 1.5-cM proximal to Xcdo365 and 1.2-cM distal to Xucw67. These new markers can be used to reduce the size of the DIC chromosome segment selected in markerassisted selection programs. Markers Nor-B2 and Xucw66 flanking the previous two markers can be used to select against the DIC segment and reduce the linkage drag during the transfer of Gpc-6B1 into commercial bread and pasta wheat varieties. The precise mapping of the high GPC gene, the high frequency of recombinants recovered in the targeted region, and the recent development of a tetraploid BAC library including the Gpc-6B1 DIC allele are the first steps towards the map-based cloning of this gene.

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-racespecific 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.

Bright yellow color, Wrmness and low cooking loss are important factors for the production of good-quality pasta products. However, the genetic factors underlying those traits are still poorly understood. To Wll this gap we developed a population of 93 recombinant inbred lines (RIL) from the cross between experimental line UC1113 (intermediate pasta quality) with the cultivar Kofa (excellent pasta quality). A total of 269 markers, including 23 SNP markers, were arranged on 14 linkage groups covering a total length of 2,140 cM. Samples from each RIL from Wve diVerent environments were used for complete pasta quality testing and the results from each year were used for QTL analyses. The combined eVect of diVerent loci, environment and their interactions were analyzed using factorial ANOVAs for each trait. We identiWed major QTLs for pasta color on chromosomes 1B, 4B, 6A, 7A and 7B. The 4B QTL was linked to a polymorphic deletion in the Lpx-B1.1 lipoxygenase locus, suggesting that it was associated with pigment degradation during pasta processing. The 7B QTL for pasta color was linked to the Phytoene synthase 1 (Psy-B1) locus suggesting diVerence in pigment biosynthesis. QTLs aVecting pasta Wrmness and cooking loss were detected on chromosomes 5A and 7B, and in both cases they were overlapping with QTL for grain protein content and wet gluten content. These last two parameters were highly correlated with pasta Wrmness (R > 0.71) and inversely correlated to cooking loss (R < ¡0.37). The location and eVect of other QTLs aVecting grain size and weight, gluten strength, mixing properties, and ash content are also discussed.

and although the main locus is referred as hardness, softness is in fact the dominant trait. The Hardness (Ha ) locus on chromosome 5D is the main determi-Biochemical studies suggested that differences exist nant of grain texture in hexaploid wheat (Triticum aestivum L.). in the binding strength of starch granules with the sur-Puroindoline (Pina-D1, Pinb-D1 ) and Grain Softness Protein (Gsprounding protein matrix between soft and hard wheat D1 ) genes are tightly linked at this locus. Additional copies of the varieties (Pomeranz and Williams, 1990). A starch sur-Gsp-1 gene are present on chromosomes 5A and 5B. Mutations in face-associated protein (M r 15kd) was found at high the Pina-D1 and Pinb-D1 genes have been individually associated levels in soft wheat and at relatively low levels in hard with grain hardness, but it is not known if mutations at both loci may