Grain hardness and slow dry matter disappearance rate in barley

Abstract

Barley grain is an important source of energy and protein for ruminant animals. However, feeding must be carefully managed to avoid maladies caused by the rapid breakdown of barley starch in the rumen. The development of slower degrading barley for ruminants may alleviate health problems associated with barley grain consumption. Selection for hard endosperm may result in slower starch degradation and improved feed quality. The objectives of this study were to: examine the effect of grain hardness, variety and environment on dry matter disappearance rate (DMDR); identify accurate and efficient hardness selection tools; and study environmental effects, inheritance and heritability of hardness.To study grain hardness and genetic and environmental effects on DMDR, two genotypes grown at multiple locations in 2004 were analyzed for Single Kernel Characterization System (SKCS) hardness, by scanning electron microscopy (SEM), and for in situ DMDR. Genotype by environment interaction influenced DMDR, while neither SKCS hardness nor SEM analysis accurately differentiated DMDR between genotypes. Eight genotypes were grown at multiple locations during 2003 and 2004 to study grain hardness measurement methodology, and genetic and environmental effects on hardness. Genotypes were analyzed for SKCS hardness, milling energy, endosperm light reflectance, feed particle size, protein and beta-glucan. Hardness measurements ranked genotypes similarly across environments. Feed particle size was correlated with milling energy but not other hardness measurements. Hardness measurements appeared to be influenced by protein and beta-glucan.To examine the inheritance and heritability of barley grain hardness, 245 double haploid (DH) genotypes and parents, grown in 2003 and 2004, were analyzed for SKCS hardness, milling energy, protein, beta-glucan, with 100 evaluated for light reflectance. The population exhibited normal distributions for SKCS hardness, milling energy, protein and beta-glucan, suggesting quantitative inheritance for these traits with no apparent epistatic gene interaction. Narrow-sense heritability was 0.75 for SKCS hardness and 0.41 for protein. Light reflectance was not normally distributed, suggesting complementary gene interaction. Broad-sense heritability was 0.53.Barley grain hardness is highly heritable and an efficient tool in making selections in a breeding program. However, breeding for high beta-glucan and protein may be better selection criteria for indirect selection of DMDR.