Submitted to: Theoretical and Applied Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/15/2008
Publication Date: 9/9/2008
Citation: Zhang, W., Chao, S., Manthey, F., Chicaiza, O., Brevis, J.C., Echenique, J., Dubcovsky, J. 2008. Qtl analysis of pasta quality using a composite microsatellite - snp map of durum wheat. Theoretical and Applied Genetics. 117:1361-1377
Interpretive Summary: Bright yellow color, firmness and low cooking weight loss are important factors for the production of good-quality pasta products. These traits generally have complex inheritance, and genes controlling the inheritance of these traits are termed as quantitative trait loci, or QTLs. However, the genes underlying those traits are still poorly understood. To fill this gap we conducted genetic analyses using materials derived from the cross between two parental lines with differences in pasta quality. The two parents used included an experimental line UC1113 having intermediate pasta quality, whereas the cultivar Kofa having excellent quality. A total of 269 molecular markers were arranged on 14 chromosomes found in durum wheat, and were used to find the association between DNA markers and quality traits. To do this, the genetic materials were grown in three different years and two separate locations in California, seeds were harvested and used for pasta quality testing. The results were then combined with marker data for statistical analyses to locate the likely chromosome locations containing genes controlling the traits. We identified QTLs largely responsible for the variation of the pasta color on chromosomes 1B, 4B, 6A, 7A and 7B. The 4B QTL was linked to a gene encoding lipoxygenase, an enzyme responsible for pigment degradation during pasta processing. In contrast, the 7B QTL for pasta color was linked to a gene encoding Phytoene synthase involved in the pigment biosynthesis. These results suggested that the genes underlying pigment metabolism are likely associated with the expression of pasta color. QTLs affecting pasta firmness and cooking weight 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. The statistical tests showed that these last two parameters were highly correlated with pasta firmness and inversely correlated to cooking weight loss. We also examined the chromosome location of other QTLs affecting grain size and weight, gluten strength, mixing properties, and ash content and their effects on the pasta quality. Generally, the analysis of full pasta quality parameters in several environments and in combination with a detailed genetic map provided valuable information to understand the genetic basis of several traits important in the determination of pasta quality.
Technical Abstract: Bright yellow color, firmness and low cooking weight loss are important factors for the production of good-quality pasta products. However, the genetic factors underlying those traits are still poorly understood. To fill 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 2100 cM. Samples from each RIL from five different environments were used for complete pasta quality testing and the results from each year were used for QTL analyses. The combined effect of different loci, environment and their interactions were analyzed using factorial ANOVAs for each trait. We identified major QTLs for pasta color on chromosomes 1B, 4B, 6A, 7A and 7B. The 4B QTL was linked to a polymorphic deletion in the Lox-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 difference in pigment biosynthesis. QTLs affecting pasta firmness and cooking weight 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 firmness (R>0.71) and inversely correlated to cooking weight loss (R<-0.37). The location and effect of other QTLs affecting grain size and weight, gluten strength, mixing properties, ash content and other quality parameters are also discussed.