A protocol for rapid screening of rice lines for seedling stage salinity tolerance

Abstract

Identification of tolerant genotypes based on phenotypic screening is one of the foremost requirements for studying genetics and molecular mapping of salinity tolerance trait in rice. For this to be accomplished efficiently, development of an efficient, reproducible, simple mass-screening protocol is imperative. The present study involves the development and validation of a modified, rapid, and reproducible protocol using sterilized silica sand as a base for growing the rice seedlings in the nutrient media replacing the generally deployed hydroponics based screening protocol where styrofoam is used as a base for seedling growth. Pre-germinated seeds were sown on silica sand filled plastic trays in three replications and modified Yoshida nutrient solution was periodically added for the first 21 days and appropriate quantities of NaCl was added to salinize the medium in different concentrations (60mM, 80mM, 100mM and 120mM). After a week of exposure to salinity, the seedlings were scored phenotypically and parameters associated with tolerance were recorded. The protocol was initially tested with known saline tolerant and sensitive rice genotypes and further validated in a set of introgressed Improved Samba Mahsuri breeding lines, possessing the QTL Saltol, which confers seedling stage tolerance to salinity. The modified protocol was able to clearly discriminate salt tolerant rice lines from sensitive ones and was superior to the routinely adopted hydroponics based protocol in terms of being more robust, reproducible, requires less nutrient solution and facilitating easy handling in screening of genotypes.