Abstract:
Twenty-one genotypes of buffel grass (Cenchrus ciliaris), and six other genotypes, viz. C. setigerus, C. Pennisetiforrnis and C. ciliaris x C. setigerus hybrids, were examined for dry matter digestibility in vitro (DMD) of recently expanded leaf and stem at anthesis. Differences in DMD were related to morphological and anatomical characteristics of the tissues.Leaf DMD ranged from 64.0 to 73.4%0 and stem DMD (internodes 2-4 from the top) from 47.4 to 61.7%; genotypes of high leaf DMD generally had high stem DMD (r= 0.68). Leaf DMD was negatively correlated with the proportion of thick-walled tissues in leaf cross-section (r= -0.76), leaf dry weight (r= 0.77 ) and specific leaf weight (r= -0.82). Stem DMD was inversely related to the proportion of lignified tissue in stem cross-section (r= -0.55), height of flowering stem (r= -0.51) and total number of vascular bundles in the stem section (r= -0.55). Genotypes with a high DMD tended to have lax leaves and small vegetative tillers.The main commercial cultivars of buffel, viz. American, Biloela and Gayndah, were 4-6% units (leaf) and 2.5-7% units (stem) lower in DMD than the best genotype, indicating potential for improvement of digestibility. Specific leaf weight and numbers of vascular bundles in stem cross-section, which arc easily and quickly measured and have a heritability comparable to that for DMD, could be useful criteria for preliminary assessment of a large breeding population.