Evaluation of salinity tolerance of lowland rice genotypes at the reproductive stage

Abstract

Salinity is an abiotic stress considered as the most widespread soil problem next to drought in rice growing areas of the world. To facilitate agricultural production on salt-affected soil, water and soil management is the most common practice, but this approach is increasingly problematic because water is becoming scarce. Therefore, developing tolerant varieties would the best solution to this problem. The present study evaluated salinity tolerance of 72 lowland rice genotypes at the reproductive stage. Experiments were conducted in irrigated fields at Marovoay, Madagascar, under low and moderately high salinity with electric conductivities of 2 dSm-1 and 4 dSm-1, respectively. A subsequent validation experiment was conducted in a pot experiment at three levels of salinity corresponding to 0, 4 and 8 dSm-1. Plant height, panicle number, panicle length, panicle fertility, spikelet fertility, straw weight and grain yield were measured together with a visual score of salt injury. Field salinity strongly reduced panicle number and spikelet fertility, reducing grain yield to less than 10 g m-2 in sensitive genotypes compared to more than 60 g m-2 in tolerant genotypes. The field experiment classified 20% of genotypes as tolerant, 50% as intermediate and 30% as sensitive to salinity. Four genotypes IR55179, MTM13_1, MTM13_3, MTM13_5, were re-confirmed as highly tolerant in the pot experiment. Higher spikelet and panicle fertility in tolerant genotypes contributed to their superior grain yield under salinity stress whereas these traits were particularly reduced in the sensitive local varieties. Genotypes with tolerance to salinity at the reproductive stage identified here could be used as donors to improve grain yield of local sensitive varieties, possibly using spikelet and panicle fertility as selection criteria for screening breeding lines at the reproductive stage.