Dry Matter Yield, Heading Date, and Plant Mortality of Orchardgrass Subspecies in a Semiarid Environment

Orchardgrass (Dactylis glomerata L.) is a highly variable, cool-season forage grass naturalized to nearly every continent. In the semiarid western United States, orchardgrass must produce forage under a semiarid summer season where supplemental irrigation is necessary, survive freezing winter temperatures, and yield when grown with later-maturing legumes. Collection efforts have garnered a diverse array of orchardgrass that includes a number of subspecies, yet none of these have been evaluated for orchardgrass breeding improvement potential in a semiarid cool-season environment. In this study, orchardgrass subspecies from high elevation origins and Mediterranean origins and those considered as ancestral to current cultivars were evaluated from dry matter yield (DMY), heading date, and plant mortality under irrigation and under nonirrigation. These accessions were compared to the cultivars Potomac, Paiute, and Latar. Accessions of high elevation subspecies and three of four Mediterranean subspecies showed significant plant mortality. The cultivars, subsp. woronowii (Ovcz.) Stebbins & Zohary accessions, and subsp. aschersoniana (Graebn.) Thell. accessions did not have significant plant mortality. Heading dates varied over 22 d, with cultivars among the earliest heading entries. For DMY, two accessions of subsp. woronowii showed equal or greater values than the three cultivars. Accessions with improved DMY and later heading dates over the cultivars were found, with potential to be used in orchardgrass selection and improvement in semiarid, cool-season environments.