Genotype by environment interactions across diverse rainfed lowland rice environments

The nature of genotype by environment (G x E) interactions in rainfed lowland rice was examined using data for 37 genotypes across 36 environments in India, Bangladesh, Thailand, Indonesia and the Philippines from 1994 to 1997. G x E interaction accounted for 32% of the total sum of squares, with environment and genotype responsible for 63% and 5%, respectively. More than 47% of the G x E sum of squares was captured by a nine genotype group by nine environment group summary. Sites with similar characteristics were tightly grouped, as were related genotypes, Environment groups included some with favourable water supply, and others with early drought, late drought, rapid-onset late drought, and submergence. Groupings of genotypes could be explained by their performance in relation to these conditions. PSBRc14, IR36 and IR64 had high yield potential and performed well over most environments, while CT9897-55-2-M-3-M and the Fl hybrids IR64615H and IR68877H also had high yield potential but only performed well with adequate water supply and where standing water remained shallow. Groups including Mahsuri, and IR62266-42-6-1 and IR57514-PMI-5-B-1-2, were stable across environments. NSG19 was preferentially adapted to environments with rapid-onset fate drought, and Sabita and KDML105 to environments favouring late maturity or recovery after drought. Implications of these results for choice and management of testing sites, and identification of suitable reference lines for the breeding program were discussed. A probe set of six lines was identified to include Sabita or KDML105, NSG19, Mahsuri, IR57514-PMI-5-B-1-2 or IR62266-42-6-1, PSBRc14 and CT9897-55-2-M-3-M, which represent broad and specific adaptations to the major target subecosystems in rainfed lowland rice systems. (C) 1999 Elsevier Science B.V. All rights reserved