A QTL on Chromosome 3B in Bread Wheat (Triticum aestivum) Is Associated with Leaf Width Under Well-Watered and Water-Deficit Conditions

At an early stage of crop development, the rate of growth is largely determined by leaf characteristics. Plants with rapid leaf area development could save more water for transpiration and crop growth. In our study, a recombinant inbred family was used to identify quantitative trait loci (QTL) controlling leaf length (LL), leaf width (LW), and leaf area (LA) in wheat seedlings under well-watered (WW) and PEG-induced water-deficit (WD) conditions. A total of five QTL for LW, LL, and LA were detected, most of which were reported for the first time. A “constitutive” QTL for LW (Qheb.LW-3B), located on the long arm of chromosome 3B, was consistently detected under two water conditions, explaining 17.7 % of the phenotypic variance with a LOD value of 7.20 under WW condition and 13.3 % of the phenotypic variance with a LOD value of 4.87 under WD condition. The other four “adaptive” QTL were detected under a single water condition only. These QTL include the following: Qheb.LW-5B for LW (WW condition), Qheb.LL-3A, and Qheb.LL-5B for LL (WD condition) and Qheb.LA-3B for LA (WW condition). Four pairs of near isogenic lines (NILs) were developed to validate the effects of Qheb.LW-3B. The allele from the parent “CSCR6” increased the LW by an average of 8.2 % under WW condition and 13.8 % under WD condition, respectively. The position and effects of Qheb.LW-3B was confirmed. Qheb.LW-3B would be a valuable genetic resource to improve wheat seedling early establishment. The NILs we have generated would be useful for further characterization of Qheb.LW-3B, in studying its interaction with other traits of agronomic importance and in developing markers that can be reliably used to follow this major locus.