Genetic variation in morphological characteristics, chemical composition and in vitro digestibility of straw from different wheat cultivars

Abstract

Straw from 15 wheat genotypes was evaluated to determine the effect of genotype on the nutritive value of straw for ruminants and if the nutritional components of the straw were related to its morphological characteristics. All the genotypes were grown in 3 replicates under the same agronomic conditions at the research farm of Agricultural University Peshawar. Genotypes strongly influenced ( P < 0.001) the nutrient composition of the straw except the crude protein contents. There were large differences ( P < 0.001) among the genotypes in the in vitro dry matter digestibility (IVDMD) of straw varying from 36.40 to 48.36%. Among the chemical components of straw, fiber fractions and NFE were significantly related to IVDMD. Significant differences ( P < 0.001) due to genotype were found in the botanical fractions of wheat straw. Leaf proportion was highly correlated with IVDMD ( r = 0.84, P < 0.001) and accounted for most of the variation in the digestibility of straw. The morphological characteristics were mostly unrelated to chemical components of the straw except crude fiber, ADF and NDF which showed negative correlations with leaf proportion and positive relationships with stem diameter and stem proportion. No relationship between grain yield and straw IVDMD was found and was genotype dependent which suggested that it should be possible to select wheat varieties that produce high quality straw without sacrifying grain yield. Increase in grain production was associated with enhanced straw yield ( P < 0.001). These observations demonstrate that wheat varieties can be identified which combine the desirable characteristics of high grain yield and high yield of superior quality straw. Among the 15 wheat genotypes, Pirsibaq-91 produced straw of higher digestibility (45.60%) and at the same time gave maximum yield of both grain and straw (3.83 and 6.90 tons per hectare, respectively). Other varieties which also combined desirable characteristics and ranked second in order of merit, included Khyber-79, Khyber-87, LU26S, Layalpur-73 and Yecora.