Genetic Variability for Chemical Composition of Alfalfa. II. Yield and Traits Associated with Digestibility1

Abstract

Quantitative genetic parameters were estimated for first harvest yield, acid detergent fiber (ADF), acid detergent lignin, in vitro dry matter disappearance (IVDMD), and protein in ‘Saranac’ and ‘MSA‐C4’ alfalfa (Medicago sativa L.). Neutral detergent fiber (NDF) and in vitro cell wall digestibility (IVCWD) were determined in Saranac. Genotypic, phenotypic, and environmental correlations among each of the characters and with concentrations of 11 mineral elements were computed for Saranac. All estimates were obtained from analysis of a series of four, five‐parent diallel crosses and their parents in each cultivar.Relatively large estimates of heritability were obtained for lignin (43.8%) and protein (64.4%) in Saranac, extremely low estimates were obtained for IVDMD in both cultivars (7.9% for Saranac and 6.1% for MSA‐C4). Heritabilities for the remaining characters wcre intermediate (22.0 to 33.8%). In breeding for improved nutritive value of alfalfa, selection for greater protein content or reduced ADF, NDF, or lignin content would be recommended over selection for greater IVDMD.Estimates of genotypic, phenotypic, and environmental correlations indicated that: (1) Yield was not strongly correlated with any of the quality parameters; (2) ADF, NDF, and lignin were positively correlated with each other and negatively correlated with IVDMD and protein; and (3) IVDMD and IVCWD were positively correlated. Althongh seldom significant, most of the correlations for mineral concentration with yield, ADF, NDF, and lignin in Saranac were negative. Protein content was positively correlated with P concentration; ADF was negatively correlated with Ca, Mg, and Fe concentrations; and lignin was negatively correlated with K concentration.