Salinity tolerant rice (Oryza sativa L.) : phenotypic-genotypic evaluation of rice genetic resources

Abstract

Salinity is one of the most severe environmental stresses that significantly reduce crop yield production worldwide. The present study was aimed to; 1) identify salinity tolerant genotypes at seedling stage in the Malaysian rice germplasm; 2) study the effects of salinity stress on rice seedling; 3) to determine the presence of salinity tolerant Saltol and SKC1 QTLs in the identified tolerant genotypes. Research was conducted using a split-plot design with three replications. The main plot was the level of salinity vis-a-vis normal freshwater at 0 dS m-1 (T1), and saline water at 4 dS m-1 (T2), 8 dS m-1 (T3), and 12 dS m-1 (T4), while the rice genotype was used as a sub-plot, respectively. A total number of 52 rice genotypes including four checks genotypes, namely Pokkali (tolerant), Nona Bokra (tolerant), IR29 (susceptible) and IR64 (susceptible) were screened. The salinity injury levels based on Standard Evaluation System (SES) scoring index and survival rate (SR) were recorded after two weeks of salinity stress treatment. Results on survival rate showed that MRQ76 completely survived 100% under 12 dS m-1 (T4) incomparable to both tolerant checks, Pokkali and Nona Bokra. Survival rate recorded the highest broad sense heritability with 0.954 followed by SES (0.69). Based on cluster analysis, the genotypes were classified into four different clusters. The Cluster I comprised MRQ76 as well as Pokkali as highly tolerant genotypes. Nona Bokra, Q70, Putra 1 and Jayanti were grouped in the Cluster II as tolerant genotypes while the rest of genotypes were classified as susceptible (Cluster III). All highly tolerant and tolerant genotypes identified were further analyzed for molecular screening. A total of 3 Saltol tightly linked SSR markers mainly RM1287, RM3412 and RM8094 were used in the screening. In addition, RM578, IM8748 and IM8854 markers were used in evaluating the presence of SKC1 QTL. Interestingly, based on those tightly linked markers, both Saltol and SKC1 were absent in the MRQ76, Q70, Jayanti, and Putra 1, respectively. This result might suggest the presence of other salinity tolerant QTLs in those genotypes. Further study on reproductive stage salinity tolerance could be suggested in future. Keywords: Salinity tolerant, rice, seedling stage, Saltol and SKC1 QTLs