A new phenotyping technique for salinity tolerance at the reproductive stage in rice

Reproductive-stage salinity tolerance has been difficult to study due to the complexity of the trait and the lack of reliable stage-specific phenotyping techniques. A leaf-cutting technique was developed with the minimum number of leaves needed by the rice plant that will not significantly affect grain yield and yield components in order to standardize rice screening for reproductive-stage salinity tolerance. Salt stress equivalent to EC 10 dSm⁻¹ was imposed to rice plants with trimmed leaves starting from boot leaf emergence up to 10 days in a pot experiment under controlled conditions. The stage-specific effect of salt stress was verified by observing saltsensitive (IR64) and salt-tolerant (IR4630-22-2-5-1-3) genotypes, as well as 201 F₂ plants derived from their cross. Leaf cutting before the booting stage efficiently directed the salt concentration to the reproductive stage and helped in discriminating the tolerant genotypes from the sensitive ones as evidenced by the low pollen viability and higher accumulation of toxic ions in the flag leaf of the sensitive genotype (IR64). The opposite was found true for the tolerant genotype (IR4630-22-2-5-1-3).