Selection of Salt-Tolerant Silage Rice Through in vitro Screening and Saltol QTL Analysis

Salinity is one of the major abiotic stressors that inhibits the growth, yield, and productivity of crop plants. Therefore, it is necessary to develop crops with increased salt tolerance for cultivation in saline soils such as is found in reclaimed land. The objective of this study was to develop a salt-tolerant silage rice line that grows on reclaimed land. In order to develop this salt-tolerant silage rice, we transferred Saltol, a major QTL associated with salt tolerance, from IR64-Saltol, a salt-tolerant indica variety, into Mogyang, a susceptible elite japonica variety. To determine the effect of salt stress, Mogyang and IR64-Saltol cultivars were grown on a medium containing various concentrations of NaCl in in vitro conditions. Shoot length was found to decrease with increasing salt concentrations, and root growth was almost arrested at NaCl concentrations over 50 mM in the Mogyang cultivar. Based on these preliminary results, we screened five salt-tolerant lines showing superior growth under salt stress conditions. Polymerase chain reaction and sequencing results showed that the introgression types of Saltol QTL were derived from the IR64-Saltol cultivar in almost all selected lines. Based on the observed growth and physiological characteristics, the new Saltol introgression lines showed higher salt tolerance compared to the Mogyang parental cultivar. The salt-tolerant lines identified in this study could be used as a genetic resource to improve rice salt tolerance.