QTL analysis of wheat kernel traits, and genetic effects of qKW-6A on kernel width

The three genetic populations used in this study included a doubled-haploid (DH) population derived from ‘Hanxuan 10’ × ‘Lumai 14’, a BC3F6 population from ‘Lumai 14’ × ‘Jing 411’ [introgression line (IL) population 1], and a BC3F6 population from ‘Lumai 14’ × ‘Shaanhan 8675’ (IL population 2). The genetic characters underpinning kernel morphological traits, such as kernel length, kernel width, kernel thickness, kernel length/width ratio, kernel length/thickness ratio, and kernel width/thickness ratio were analyzed. Quantitative trait loci (QTL) for all the above traits were mapped in the three populations across six, three, and three environments, respectively. The genetic effects of qKW-6A, which was detected in all three populations, were analyzed. Forty six additive QTLs for kernel morphological traits were detected in the DH population, and 20 additive QTLs were detected in each of the IL populations. A kernel-width QTL, qKW-6A, was located within the same interval in all three populations. qKT-7A-3, qLTR-4A, and qWTR-7A-1 mapped in the DH population were located in the same marker intervals as qKT-7A-1, qLTR-4A, and qWTR-7A-1, respectively, in IL population 2. qLWR-5A-2, qWTR-5A-2, and qWTR-5A-1 from the DH population were detected in five, four, and three environments, and explained 14.72, 25.11, and 25.91%, respectively, of the phenotypic variation. qLTR-7A from IL population 1 and qLWR-5B from IL population 2, detected in all three environments, explained 6.10 and 10.66% of the phenotypic variation, respectively. On the other hand, negative alleles of qKW-6A for kernel width detected in all three populations were derived from ‘Lumai 14’. Donor segments including this QTL were introgressed into 18 lines of IL population 1 and 44 lines of IL population 2. The mean kernel width in these lines was greater than the recurrent parent ‘Lumai 14’ under drought-stress conditions in 2 years, indicating that qKW-6A played an important role in determination of kernel width. Line 157 from IL population 2 contained only five chromosomal segments from the donor parent, and these donor segments harbored no QTL for kernel width other than qKW-6A. However, kernel width in this line was significantly greater than that of ‘Lumai 14’ in all three environments. Thus, Line 157 can be regarded as a near-isogenic line for fine mapping and map-based cloning of qKW-6A.