Consistency of genotypic performance of lowland rice in wet and dry season in Lao PDR

Abstract

Lowland rice in Laos as in some other SE Asian countries is grown mostly under rainfed conditions in wet season (WS), but some crops are grown under irrigated conditions in dry season (DS). In Laos, the rice breeding program is concentrating on development of photoperiod insensitive varieties which can be grown in both WS and DS, nevertheless most selection is conducted in WS. In order to determine consistency of genotypic performance between WS and DS, 23 advanced breeding lines and varieties were grown in both seasons for 2–3 years at four locations in the country. All experiments in DS showed significant genotypic variation for grain yield, while genotypic variation was smaller and often not significant in each experiment in WS. The heritability was also higher in DS than in WS. Significant genotype-by-environment interaction was found, and some of this interaction was due to long duration genotypes being affected by extreme temperature conditions in DS particularly at a high altitude location in Northern Laos. Cluster analyses indicate that the genotypic discrimination was large in experiments with intermediate yield levels (mean yield of 2.9–3.8 t/ha). It is concluded that the use of DS trials should be increased to improve the efficiency of selection for widely adapted varieties in the lowland rice breeding program in Laos and other countries of similar growing conditions.