Stover quality of dual-purpose sorghums: genetic and environmental sourcesof variation

Improvement of the nutritive value of dual-purpose sorghum (Sorghum bicolor (L.) Moench) stover is an important objective for the semi-arid tropics wh ere sorghum crop residue is extensively used for livestock feed. To identif y the relative importance of genetic and environmental sources of variation for nutritive value, leaves and stems of six diverse dual-purpose sorghum cultivars were evaluated fdr in vitro gas production (Gas48hr), neutral det ergent fiber (NDF), acid detergent fiber (ADF), lignin, nitrogen, and ash c ontents under two fertility and two plant-density regimes during 2 years in India. Substantial genotypic differences were observed for stem Gas48hr (2 5.7 to 33.0 ml in 200 g(-1) dry matter (DM)) and NDF (564-687) content. Gas 48hr and NDF content of stems exhibited more promise as selection criteria than those of leaves, as stems showed larger portion of variation attribute d to genotypes, relatively less genotype by environment (GE) interactions, and were closely related to whole-plant values. Year, nitrogen fertilizatio n and plant density showed very little influence on Gas48hr, NDF or ADF of leaves and stems. Gas48hr exhibited substantial GE interactions with all en vironmental factors, indicating the need for multi-environment testing to a chieve progress. (C) 2001 Published by Elsevier Science B.V.