HERITABILITIES OF MORPHOLOGICAL AND AGRONOMIC TRAITS IN WESTERN WHEATGRASS

Limited research has been directed towards characterizing the phenotyp ic and genotypic variability of different traits in North American pla nt species. This study was conducted to estimate the degree of genetic control, i.e., the heritability (h2), of several agronomic and morpho logical traits of ND-WWG931 western wheatgrass [Pascopyrum smithii, (R ydb.) Love] and to provide insight into appropriate sample sizes neede d to estimate genetic parameters. Thirty randomly selected half-sib fa milies of ND-WWG931 western wheatgrass were evaluated over 2 years and 2 locations in seeded single-row plots. Heritabilities were determine d for the following traits based on the progeny means of the 30 famili es: dry matter yield, tiller height, spikelets per spike, vigor, spike density, spike pubescence, and spikelet color. Spike density, dry mat ter yield, and vigor had relatively high heritabilities (h2 = 79, 72, and 67%, respectively) and were estimated with the greatest precision (90% confidence interval width range: 33 to 64% as large as the point estimate). Spike pubescence, spikelets per spike, tiller height, and s pikelet color demonstrated moderate to low heritabilities (h2 = 55, 49 , 33, and 0% respectively) and were estimated with the least precision as demonstrated by relatively wide confidence limits. The genetic var iance components for spike density, forage yield, vigor, and spike pub escence exceeded twice their standard errors indicating that selection for these traits should be effective in ND-WWG931. Heritability estim ates of fresh forage yield were essentially the same, i.e., 61.9 and 6 1.5%, when based on either 30 or 270 half-sib families, respectively, indicating that a sample size of 30 families was adequate to provide r eliable estimates of genetic variance in ND-WWG931. These data provide general insight into the population genetics of a North American plan t species and demonstrate an approach to determine the genetic variabi lity within plant materials that are being used for rangeland revegeta tion.