Experimental analysis of genetic and environmental interactions on leaf elongation and reproductive development in <i>Lolium perenne</i>

Perennial grasses' reproductive phenology profoundly impacts plant morphogenesis, biomass production, and perenniality in natural ecosystems and cultivated grasslands. Complex interactions between vegetative and reproductive development complicate grass phenology prediction for various environments and genotypes. This work aims to analyse genetic × environment interactions effects on tiller growth and reproductive development in <i>Lolium perenne.</i> Three perennial ryegrass cultivars, Bronsyn, Carvalis, and Tryskal, were grown from seedling to heading under four inductive conditions. T0 plants were continuously exposed to high temperatures and long days (HT-LD). T1, T2, and T3, plants were initially exposed to low temperatures and short days (LT-SD) for 9 weeks. Then, T1 plants were immediately transferred to high temperatures and long days (HT-LD). Before their exposure to HT-LD, T2, and T3 plants were first transferred to high temperatures and short days (HT-SD) for 3 and 6 weeks, respectively. Leaf length, leaf emergence, and heading were regularly monitored. Floral transition and heading only occurred in T1, T2, and T3, i.e. after successive exposure to low temperature and long photoperiod. Bronsyn had higher heading earliness and proportion of reproductive tillers than Carvalis and Tryskal. The duration of HT-SD exposure affected the final number of leaves and spikelets. The rate of leaf and spikelet production significantly increased once plants were exposed to LD. Our results suggest an additive effect of the photoperiod and floral transition on leaf elongation rate. These findings enhance our understanding of the genetic × environment interactions on the vegetative and reproductive development in perennial ryegrass.