Forage Yield and Quality of Tall Wheatgrass Accessions in the USDA Germplasm Collection

Tall wheatgrass [Thinopyrum ponticum (Podp.) Liu and Wang] is a cool-season bunchgrass from southern Europe and Asia Minor that is tolerant to saline or alkaline soils. The genetic base of tall wheatgrass cultivars is narrow. The lineages of four of the six cultivars of tall wheatgrass developed and released in the USA and Canada trace to a common accession, PI 98526. The objective of this study was to determine the extent of variation in the USDA collection of tall wheatgrass for forage quality, yield, and other agronomic traits. All available accessions of tall wheatgrass (n = 50) from the USDA Western Regional Plant Introduction Station at Pullman, WA, and two check cultivars, Platte and Jose, were used in the study. Greenhouse grown seedlings were transplanted in 1989 into a replicated field evaluation nursery located about 35 km west of Omaha, NE. An evaluation plot consisted of a single row of 10 plants spaced on 1.1-m centers. The experimental design was a blocks-in-replicates design with two replications. The plots were evaluated for forage yield and quality including in vitro dry matter digestibility (IVDMD), protein content, and other traits in 1990 and 1991. Several of the PI lines had forage yields equivalent to the check cultivars. One accession, PI 98526, had higher first harvest IVDMD than the check cultivars; other accessions had IVDMD values equivalent to the check cultivars. In addition to having high yields and high IVDMD, these accessions also were equivalent to the check cultivars in other agronomic traits as indicated by high leafiness and inflorescence scores. The results indicate that superior germplasm exists in the USDA tall wheatgrass germplasm collection that can be used to develop improved cultivars of tall wheatgrass with improved forage quality as measured by IVDMD