Evaluation of salinity tolerance of lowland rice genotypes (Oryza sativa L.) at the reproductive stage

Developing salt tolerant varieties is the best solution to the increasing soil salinity problem of rice growing areas all over the world. This study evaluated salinity tolerance of 72 lowland rice genotypes at the reproductive stage in field experiments conducted in coastal Marovoay, Madagascar. Field salinity levels were controlled at 2 and 4 dS m-1 through irrigation. Tolerance of selected genotypes was validated in pot experiments with salinity levels of 0, 4 and 8 dSm-1. Plant height, panicle number and length, panicle and spikelet fertility, straw weight and grain yield were measured together with visual scores of salt injury. Field salinity strongly reduced panicle number and spikelet fertility, reducing grain yield to 10 g m-2 in sensitive genotypes compared to 60 g m-2 in tolerant genotypes. Thus, 20% of genotypes were classified as tolerant, 50% as intermediate and 30% as sensitive to salinity. Four genotypes IR55179, MTM13_1, MTM13_3, MTM13_5, were confirmed as highly tolerant in the pot experiment. Higher spikelet and panicle fertility in tolerant genotypes contributed to their superior grain yield under salinity. These genotypes can serve as donors to improve grain yield of local varieties sensitive at the reproductive stage, possibly using spikelet and panicle fertility as selection criteria. Key words: Salinity, reproductive stage, growth parameters, salt tolerance, genotypes.