Genetic Variances of Agronomic Traits in Tetraploid Crested Wheatgrass under Competitive Conditions

Abstract

Limited research has been conducted on characterizing the genetic variability of important agronomic traits of forage grasses grown in seeded swards. This study was conducted to estimate the degree of genetic control, i.e., the beritability (h2), of several agronomic, morphological and physiological traits of crested wheatgrass [Agropyron desertorum (Fischer ex Link) Schultes] under sward conditions. Thirty randomly selected half‐sib families from a genetically broad‐based crested whcatgrass population were evaluated at one location for 2 yr in single‐row plots that were spaced 38 cm apart and seeded at a rate of 90 seed m−1. Heritabilities were determined for the following traits based on the progeny means of the 30 families: fresh forage yield, dry matter yield, tiller height, tiller number, flag leaf width, spikelets per spike, proline content, first‐cut vigor, regrowth vigor, and flag leaf pubescence. Heritability estimates of fresh forage yield were similar, i.e, 80 and 82%, when based on 30 and 300 half‐sib families, respectively, indicating that a sample size of 30 families provided a reliable estimate of genetic variance in this crested wheatgrass population. With the exceptions of tiller number and proline content (h2 = 0%), all traits demonstrated moderate to high heritabilities, ranging from 53 to 86%. Confidence interval widths ranged from 14 to 116% as large as the heritability point estimate. Signilicant family × year interactions were detected for some traits that possessed moderate to high heritabilities. The interaction variance components, however, were significantly less than their corresponding genetic variance for all traits except first‐cut vigor. The results indicate that for most traits, evaluation for multiple years would not be needed.