Genotype-by-environment interaction is important for grain yield in irrigated lowland rice

Irrigated rice contributes the most to rice production globally and in most of rice producing countries. As with other rice production ecosystems, genotype and growing environment are the main factors influencing grain yield (GY) in irrigated rice production. However, the relative importance of genotype, environment and genotype-by-environment interaction (GEI) on GY is less studied for irrigated rice, although evaluation of candidate varieties for yield stability through multi-environment trials before release and registration is mandatory in many countries. To identify patterns of genotype, environment, and GEI for GY of irrigated lowland rice, 392 cultivars or advanced breeding lines mostly from the International Rice Research Institute (IRRI), PhilRice (Philippines) and a few breeding programs of other countries were evaluated for GY and related traits in eight environments including Jiangxi (JX) and Sichuan (SC) in China, and six season (2) and nitrogen rate (3) combinations at IRRI headquarters (Los Baños, Philippines). Wide ranges of variations across genotypes and environments were observed for all traits. Genotype, environment, and GEI all significantly affected GY and some of the yield associated traits. GEI was more important than genotypic main effect for GY, seed setting rate and the number of panicles per plant but less important for other traits. For GY, the genotype-by-season interaction and genotype-by-season-by-nitrogen interaction was more important than the genotype-by-nitrogen interaction. The 303 genotypes with GY data in all environments were clustered into ten groups based on GY using an agglomerative hierarchical clustering procedure. The eight environments were grouped into three groups based GY using the additive main effects and multiplicative interaction (AMMI) analysis. Three nitrogen rates in the WS and SC were grouped together (E1), while three nitrogen rates in the DS formed another group (E2). JX alone was the third group (E3). Genotype groups GG9 and GG3 had the highest GY across the eight testing environments. GG9 had the highest yield in E1 and E2 while GG10 was the best in E3.