| Protein content is an important component of durum wheat quality. The Langdon-Triticum turgidum L. var. dicoccoides chromosome 6B substitution line (LDN(DIC-6B)) contains genetic factor(s) that increase grain protein content. Here we report the introgression of this high grain protein genetic factor(s) into adapted durum germplasm and molecular mapping to verify the 6B chromosomal region associated with protein content. A recombinant inbred population segregating for high grain protein was developed from the LDN(DIC-6B) with two doses of adapted germplasm. This population was evaluated in the field for grain protein content, yield, and other agronomic characteristics in two locations in 1995 and three locations in 1996. Results from segregation analysis for grain protein fit a bimodal distribution indicating a single genetic factor or a tightly linked gene cluster controlling high grain protein. Analysis of this character using simple regression and interval mapping procedures identified a locus near Xcdo365 and Xmwg79 on chromosome 6B having a major effect on grain protein content. Therefore, the region detected in this study corresponds to the chromosomal region reported by Joppa et al. (1997). This locus explains up to 72 percent of the phenotypic variance and accounts for a 15 g kg{dollar}sp{lcub}-1{rcub}{dollar} increase in average protein concentration. The expression of this locus is independent of genetic background, environmental conditions, protein quality, agronomic traits, and grain yield. Markers CDO365 and MWG79 are a valuable and highly effective selection tool in durum wheat breeding programs that are utilizing the LDN(DIC-6B) line to improve grain protein. |
