Fifty-four years of ryegrass ear phenology reveals climate change responses

Abstract

New perennial ryegrass (Lolium perenne L.) cultivars undergo field tests that compare them to all protected cultivars, registering those that are novel and rejecting facsimiles. This involves over-wintering in short-days/low-temperatures to prime plants to initiate reproductive growth when cultivar specific Spring photoperiods are inductive, with subsequent timing of seed-head emergence recorded. Comparing emergence dates over 54 years (1969–2023), on nine indicator groups spanning earliest to latest maturing cultivars, revealed a progressive drift towards earlier emergence, with more compressed distributions in recent years. Analysis of cultivars with 10 + concurrent years confirmed a phenological dependency on incident growing conditions between initiation and emergence, independent of cultivar genotype. Quantifying climatic accumulations between initiation and emergence, revealed that earlier ear emergence was positively and significantly correlated with daily temperature and irradiation trends, but weakly associated with highly variable rainfall. This phenological timing is also annually recorded on a wide diversity of agricultural, amenity, ornamental and vegetable species, at internationally dispersed test centres. Therefore, this study identifies hitherto unrecognised opportunities to interrogate precise and standardised plant responses to changing climatic conditions. As Climate Change impacts vary regionally, such a novel biological indicator network could monitor plant phenology responses to mitigation measures, and globally compare regional impacts on both farmed and natural plant systems.