QTL mapping for yield and yield-contributing traits in sorghum (Sorghum bicolor (L.) Moench) with genome-based SSR markers

In recent years, sorghum (Sorghum bicolor (L.) Moench) has gained attention as a food, feed, and biofuel crop, but yield improvements have lagged behind those in other crops. Here, we investigated quantitative trait loci (QTLs) associated with yield and yield-related traits in sorghum. We measured eight morphological traits related to yield potential in an F2 and F2:3 population derived from a cross between African and Japanese sorghum landraces, and we developed a genetic linkage map of 137 sorghum genome-based simple sequence repeat markers. The total map length was 1,239.2 cM, with an average distance of 9.9 cM between adjacent markers. By using both single- and multiple-QTL approaches to identify the chromosomal regions controlling these traits, we identified a total of 52 QTLs associated with the eight traits (culm length, number of tillers, panicle length, culm diameter, leaf length, leaf width, grain weight/panicle, and 100-grain weight) using F2 phenotypic values while 25 QTLs were confirmed in the F2:3 population. The percentage phenotypic variation explained by individual QTLs ranged from 3.1 to 36.3 % in the F2 and 2.1 to 30.4 % in the F2:3 population. Most of the traits were significantly correlated with one another (P < 0.05). Ten QTLs had a significant association with more than one trait. A QTL for culm length was mapped to the same region of chromosome 7 as the dw3 gene for plant height. The major QTLs identified here are expected to provide useful information toward understanding the genetic mechanisms of important agronomic traits related to yield in sorghum.