Repeated submergence stress impairs yield despite improved survival in rice

Abstract

Submergence stress is a major constraint to rice production in flood-prone areas. Acclimation responses are well-documented for many abiotic stresses in rice; however, the ability of rice to acclimate to repeated submergence stress periods remains unexplored. In this study, we evaluated 15 rice varieties under both single- and double-submergence stress conditions to determine whether prior exposure enhances submergence tolerance. Repeated submergence significantly reduced grain yield (GY) across most genotypes, despite improved or sustained survival in submergence-tolerant varieties. Correlation and multivariate analyses revealed that GY was strongly associated with survival, tiller number, and panicle number, whereas shoot elongation contributed little to yield variation. Although some genotypes exhibited enhanced survival following repeated submergence, this advantage did not translate into improved yield, indicating that acclimation responses are limited to survival and did not extend to productivity. These findings highlight the need for breeding strategies that integrate survival with post-submergence recovery and yield stability under recurrent flooding conditions.