Effect of Moderate Drought-Stress on Flowering Time of Interspecific Hybrid Progenies (Oryza sativa L. × Oryza glaberrima Steud.)

We examined the effects of drought stress on flowering time, grain yield, and agronomic traits using 10 upland-adapted rice genotypes, i.e. eight interspecific Oryza sativa L. ~ Oryza glaberrima Steud. (NERICA) lines and two Oryza sativa varieties—WAB56-104, the O. sativa parent of eight interspecific lines and IRAT 109, a drought-resistant variety as a check—under wet control and moderate drought-stressed conditions. Analysis of variance results for the 10 rice genotypes indicated that the effects of genotype (G) and drought stress (environment, E) were highly significant for tiller number, spikelet fertility, grain yield, straw dry-matter weight, and harvest index. Flowering was delayed by 1.7.10.7 (4.5 on average) days under drought condition compared with that under the wet control condition. Genotype (P < 0.001), drought stress (P < 0.001), and G ~ E interaction (P < 0.001) were highly significant with respect to days from seeding to 50% flowering (DTF50). DTF50 was significantly and negatively correlated with grain yield, yield components, and harvest index under drought-stress conditions. Of these, panicle number, total spikelet number, spikelet fertility, grain yield, and harvest index in drought-stressed rice genotypes were significantly and negatively correlated with DTF50 compared with those under the wet control condition. In conclusion, drought during the early vegetative stage inhibits most of the major agronomic traits by delaying flowering in upland-adapted rice genotypes.