Divergent Selection for Anthesis of Annual Ryegrass (Lolium perenne ssp. multiflorum (Lam.) Husnot)

Annual ryegrass (Lolium perenne ssp. multiflorum (Lam.) Husnot) is a prolific species expanding into winter-fallow row crop fields of the southeastern US. While its dense growth makes it an excellent cover crop, late senescence, and herbicide resistance pose challenges for spring eradication. This study aims to develop an annual ryegrass population that naturally senescences early by employing recurrent phenotypic selection to alter anthesis date. In 2022, a base population was collected with anthesis dates from 21 March to 2 April, (mean anthesis date of 28 March). The base population was allowed to polycross in isolation. To obtain Cycle0, 903 seedlings of this population were grown under ambient winter conditions at Starkville, MS. Upon anthesis, the Cycle0 individuals were segregated into three groups: the “NV0” group consisting of 11 non-vernalizing progenies, the “E0” group consisting of the 70 progenies earliest to anthesis, and the “L0” group, comprising the last 70 individuals to reach anthesis. Isolated groups were allowed to polycross within each group to give three new populations of Cycle1: NV1, E1, and L1 in 2023. Genetic variation was used to predict a gain due to selection for the anthesis date. The results observed exceeded the predicted gain of 6 days. Groups NV1, E1, and L1 had a gain of 18, 14, and 10 days, respectively, and heritability (h2) of 0.39, 0.61, and 0.45, respectively, for anthesis. The NV and E populations will be assessed for usefulness as a cover crop and L as an enhanced forage variety.