Characterising genetic variation in tillering in sorghum

Tillering can make an important contribution to grain yield in sorghum, but is strongly affected by both genotype (G) and environment (E). Despite genetic variation for the trait, previous studies have been confined to a limited number of genotypes and the physiological mechanisms and causes of genotypic differences in tillering in sorghum remain unclear. To exploit the trait in sorghum improvement, the genotypic and environmental effects on tillering and their interactions need to be understood. The present study aims to explore the extent and nature of genetic variation for tillering in sorghum and the interaction of these genetic effects with variation in environment. A set of 90-100 lines and hybrids with diverse origin but structured genetic background was characterized for tillering and related traits in both a low tillering (glass house environment with low light intensity) and a high tillering (spaced planting in the field) environment. Tiller number per plant varied from 0-8 and 0–16 in the low and high tillering environments respectively. Comparisons between the ranks in the two experiments indicated that GxE for tillering was significant. Results for hybrids indicated that the expression of tillering is primarily additive, although partial dominance was present in some hybrids. Significant correlations of leaf width and internode diameter with tillering indicated a possible involvement of these traits in the regulation of tillering. An analysis of combining ability revealed the potential of SC62C as a germplasm source for high tillering. The wide range of variation in tillering also provides the basis for future mapping studies