Salt stress is a major limiting factor for crop production across the world. Rice is particularly sensitive to salinity, with both plant growth and grain yield significantly impaired under saline conditions. However, the ability to tolerate salt differs with the growth stages of the plant as well as varying across different varieties of rice. Some wild relatives of rice have been found to be quite tolerant of salty conditions. Harnessing this variation could allow new salt-tolerant varieties of rice to be bred and would provide more choice of rice varieties to farmers.
In a recent study published in AoBP, Mitsuya et al. developed chromosome segment substitution lines (CSSLs) from Nona Bokra, a salt-tolerant indica landrace, with the genetic background of Koshihikari, a salt-susceptible but leading japonica variety. These were screened to find lines that performed better than Koshihikari under long-term saline conditions. SL538 showed higher grain yield and grain filling than Koshihikari under salinity, however this was not attributed to Na+, Cl– or K+ homeostasis. SL501, 502 and 503 on the other had maintained grain weight under salinity compared with Koshihikari and was related to lower Na+ concentrations in leaves and panicles. The results of this study imply that there is independent genetic control of salt tolerance of each yield component, and that it may not always be related to superior salt exclusion ability. The authors hope that the results from this study will drive future work that will identify the genetic determinant of salt tolerance in the Nona Bokra landrace and contribute to future breeding efforts.