Differential growth response and carbohydrate metabolism of global collection of perennial ryegrass accessions to submergence and recovery following de-submergence

Submergence can severely affect the growth of perennial grasses. The variations in growth and the physiological responses of perennial grass germplasm to submergence stress are not well understood. The objective of this study was to characterize the responses of diverse perennial ryegrass accessions to submergence and their recovery following de-submergence. One hundred globally collected perennial ryegrass accessions were submerged for 7d followed by 7d of recovery in two experiments (Exp 1 and Exp 2), respectively. Compared to the pattern of the controls, the overall distribution in leaf color, chlorophyll fluorescence, plant height (HT), and growth rate (GR) shifted toward a high frequency of lower values under submergence in both experiments. The accessions were generally grouped into three types: fast growth with maintenance of color (escape, T1), slow growth with maintenance of color (quiescence, T2), and slow growth with loss of color (susceptible, ST). Under submergence, T1 had higher HT and GR than the other two groups except for GR of T2 in Exp 2 and had higher water-soluble carbohydrate (WSC) and fructan concentrations, as well as fructan to WSC ratio, than ST in Exp 1. Recovery of HT and GR were generally close to that of the control level except for HT of ST in Exp 2, but the carbohydrates fully recovered in all types of plants after 7d of de-submergence. Differential responses of perennial ryegrass accessions to submergence are useful in creating more tolerant materials and in further characterizing physiological and molecular mechanisms of submergence tolerance.