Quantitative Trait Loci of Plant Attributes Related to Sorghum Grain Number Determination

The genetic basis of grain number determination in sorghum [Sorghum bicolor (L.) Moench] was studied based on canopy growth traits. Traits were crop growth rate (CGR) around flowering, plant reproductive biomass partitioning (P-R) to the panicle, and grain-set efficiency (E-G) per unit of accumulated panicle biomass. Previous evidence has shown that these traits vary across commercial germplasm and that P-R and E-G are genotype-specific traits with low environmental effects. Our hypothesis was that P-R and E-G are highly heritable traits correlated to grain number (and yield) for which environmentally consistent quantitative trait loci (QTL) could be detected. Studied recombinant inbred lines (RILs) showed important variation in yield, grain number per square meter, time to anthesis, plant height, CGR, P-R and E-G, and growth environments created significant genotype 'environment interactions for most. Variability in grain number per square meter was significantly correlated with P-R (p < 0.001) and E-G (p < 0.001) but not with CGR (p > 0.05). Heritability estimates for P-R and E-G were larger than estimates for CGR, grain number per square meter, or yield. A multitrait, multienvironment approach over CGR, P-R, and E-G identified 12 QTL (LOD >= 2.5), explaining 21 to 36% of observed trait variability. No QTL were detected for CGR, while two and one environmentally consistent QTL were found for P-R and E-G, respectively. Results highlighted relevant information that could be potentially exploited in breeding programs.