Involvement of peduncle elongation, anther dehiscence and spikelet sterility in upland rice response to reproductive-stage drought stress

Abstract

Reproductive stage drought stress results in dramatic reduction of spikelet fertility and grain yield of upland rice ( Oryza sativa L.). The hypothesis investigated here is that spikelet sterility under pre-anthesis drought is triggered by deficient plant water status that inhibits peduncle elongation, panicle exsertion and anther dehiscence. A set of 45 rice genotypes was grown in an upland field under well-watered and drought-stressed conditions. Irrigation was applied using a drip irrigation system, and the drought stress treatment was initiated differentially for each genotype at 10–15 days before heading. Drought stress substantially reduced grain yield, and the average yield in the drought treatment was only 20% of that of the control. Peduncle elongation rate (PER) was significantly inhibited by drought, simultaneously with the decrease of plant water status parameters. Yield was highly associated with spikelet fertility ( r = 0.74***), PER ( r = 0.47***), leaf water potential (LWP) ( r = −0.4**), and peduncle water potential (PWP) ( r = −0.38**). The sensitivity of anther dehiscence to drought stress, as determined by the anatomic structure of anther walls, did not differ among genotypes. Path analysis revealed that spikelet fertility and PER had a major positive effect on yield, while peduncle length and LWP had negative effects. PWP had a small direct effect, but had a high negative indirect effect on yield through spikelet fertility reduction. PER had a high and positive indirect effect on yield under drought through spikelet fertility. It is concluded that PER is key parameter that affects rice yield through the regulation of spikelet fertility by plant water status under drought.