Abstract: Heat threatens rice yield and grain quality, yet seedling heat-shock phenotypes often provide limited guidance for reproductive or grain-filling performance. This review synthesizes rice genetic evidence connecting early signaling, protein and membrane protection, reproductive resilience and endosperm homeostasis. We organize natural alleles and engineered interventions by developmental stage, heat regime and the extent of agronomic validation. An inventory of 41 rice modules identifies a persistent gap between mechanistic understanding and breeding application. Five interventions meet the stated minimum for replicated field evidence, whereas the others require further stage-matched agronomic or environmental validation. Rice studies of OsALA5, TT2, NAT1, OsNRT2.3, and QT12 illustrate distinct routes to membrane stability, wax regulation, carbon allocation and grain-quality protection. Evidence from other species is retained only where it defines an unresolved rice mechanism. We propose phenotyping that connects measured thermal exposure and recovery with fertility, grain quality and yield across independent field environments. Tunable, tissue-specific and heat-responsive regulation offers a basis for testing allele combinations while monitoring growth and immunity costs. These priorities connect rice heat-response mechanisms with the validation needed for cultivar improvement.

Key words: rice, heat stress, thermotolerance, reproductive development, grain quality, phenotyping, molecular breeding