Effects of Soil Salinity and Alkalinity on Grain Quality of Tolerant, Semi-Tolerant and Sensitive Rice Genotypes

Soil salinity and alkalinity adversely affects the productivity and grain quality of rice. The grain quality of 19 rice genotypes characterized as salt tolerant (T), semi-tolerant (ST) and sensitive (S) was assessed in lysimeters containing saline and highly alkaline soils. Head rice recovery was reduced by salinity stress whereas it was not affected by alkalinity stress. The ratio of length to width (grain dimensions) was significantly reduced in the T genotype even at low electrical conductivity (EC, 4 mS/cm) and alkalinity (pH 9.5), whereas in the ST genotype, it was significantly reduced at high salinity (EC 8 mS/cm). There was no significant effect of any levels of salinity or alkalinity on grain dimensions in the S genotype. Amylose content was significantly reduced in T and ST groups even at low EC (4 mS/cm) and alkalinity (pH 9.5) and the effect in the S genotype was only at high salinity. Starch content showed significant reduction at high salinity and alkalinity (EC 8 mS/cm and pH 9.8) in the T and ST genotypes and no significant effect was observed in the S genotype. The effect of both levels of salinity (EC 4 and 8 mS/cm) and high alkalinity (pH 9.8) on gel consistency was observed only in the S genotype. The tolerant genotypes IR36 under high salinity, and CSR10 and CSR11 under alkali stress showed less reduction in amylose content. The T genotype BR4-10, and ST genotypes CSR30, CSR29 and CSR13 showed better gel consistency under saline and alkali stress. Amylose content was affected even at low salinity stress and thus important to be considered in breeding rice for salt tolerance. Overall, the grain quality of T and ST genotypes was less affected by saline and alkali stress compared to S ones.