Heritabilities of Nutritive Quality Factors and Interrelationships with Yield in Tetraploid Crested Wheatgrass

Abstract

Detailed information on the genetic variation of forage quality traits and their relationship with forage yield under seeded competitive conditions is limited in crested wheatgrass. This research was conducted to determine the heritabilities (h2), of forage quality parameters in tetraploid crested wheatgrass [Agropyron desertorum (Fischer ex Link) Schultes] grown under competitive conditions. Genetic correlations among nutritive quality traits and yield were also determined. Thirty randomly selected half‐sib families from a genetically broadbased crested wheatgrass population were evaluated at one location from 1991 to 1992 in single‐row plots that were 1.5 m long, spaced 38 cm apart, and seeded at a rate of 90 seed m−1. Heritabilities were determined for crude protein, in vitro digestible dry matter (IVDDM), neutral detergent fiber (NDF), acid detergent fiber (ADF), and hemicellulose based on the means of the 30 families. Variation among families was significant (P ≤ 0.01) for all traits. Heritability estimates (approaching narrow sense heritability) for IVDDM, crude protein, NDF, ADF, and hemicellulose were 50, 53, 63, 68, and 72%, respectively. Genetic correlations indicated that digestibility was positively associated with crude protein (r = 0.65; P < 0.01) and negatively influenced by NDF and ADF (r = − 0.79 and − 1.04; P < 0.01). Genetic correlations between forage quality traits and yield were low under competitive conditions indicating that independent selection for each trait would result in improved forage quality and yield. Interaction variance components were significantly different from zero, and rank correlations between years were low for most forage quality traits. The data indicated that maximum gain in nutritive quality improvement in crested wheatgrass may require multiple years of evaluation.