Genetic Variability for Cell Wall Constituents and Associated Quality Traits in Reed Canarygrass1

Abstract

Forage dry matter intake potential by ruminants is negatively associated with its cell wall constituent (CWC) concentration. The objectives of this study were to estimate genetic variance components and determine combining ability and heritability of CWC percent, and other associated quality traits in reed canarygrass (Phalaris arundinacea L.). Genotypic correlations were computed between paired characters. Twelve heterozygous clones used in two 6 ✕ 6 diallels and progenies from 30 crosses were grown for 2 years at two locations with three replicates arranged in randomized complete blocks. One plot consisted of six plants on 91 cm spacing in a row. Infrared spectroscopy was used to determine CWC, acid detergent fiber (ADF), acid detergent lignin (lignin), silica, crude protein, and in vitro digestible dry matter (IVDDM). Separate predictive equations were necessary for each year, probably due to yearly differences in drying procedures of samples. General (GCA) and specific combining ability (SCA) were estimated least squares analysis for one harvest in 1976, two harvests in 1977, and for the mean of the three harvests.Mean squares for GCA were significant for CWC, ADF, and lignin. Mean squares for SCA were significant for CWC, ADF, lignin, crude protein, and IVDDM. Estimates of variance components due to SCA were nearly twice as large or larger than the variance components due to GCA for CWC, ADF, lignin, crude protein, and IVDDM, indicating the presence of large amounts of nonadditive genetic variance under noncompetitive, spacedplant conditions. Broad‐sense and narrow‐sense heritabilities for CWC were 0.81 and 0.26, respectively.Estimates of genotypic correlations suggested that: (i) CWC was strongly positively correlated with ADF and lignin and strongly negatively correlated with protein and IVDDM; (ii) ADF had the highest correlation with IVDDM and was closely followed by lignin and CWC, which agreed with other reports using laboratory procedures for estimating these traits; (iii) none of the quality components was strongly correlated with spaced‐plant yield of first growth.