SALT TOLERANCE STUDIES IN COTTON (Gossypium spp.)

Rajgopal

SALT TOLERANCE STUDIES IN COTTON (Gossypium spp.)

Date

1999

Authors

Rajgopal

Publisher

University of Agricultural Science, Dharwad

Abstract

"Investigation on salt tolerance in cotton was made with nine genotypes, belonging to Gossypium arboreum (AK 235, CIMA 302 and AKH 4) G. herbaceum (Jayadhar and Dhumad) and G. hirstum (JK-276-10-5, JK 345-3-3, LRA 5166 and AK 84635), under five salinity levels in pot and field conditions. The objective was to study the changes in physiological, biochemical parameters, yield potential and their relationship under varying salinity levels and finally to find out the mechanism of salt tolerance in cotton. The results showed that germination, shoot and root vigour index, leaf area and total dry matter (30 and 60 DAS) decreased with increase in salinity level. The relative decrease was lower in AK 235 and LRA 5166 as compared to other genotype. Stomatal density Increased while stomatal conductance, stomatal size, transpiration rate, photosynthetic rate and osmotic potential decreased with increase in salinity level. The genotype AK 235 showed lower reduction in these characters whereas maximum reduction was observed in AKH 4. Sodium content in stem and leaf increased with increase in salinity, while potassium and calcium content decreased. At higher salinity levels K/Na ratio was maintained in genotypes AK 235, AK 84635 and LRA 5166 by restricting Na+ uptake and increased K+ uptake in to the shoot indicating salt tolerance. In general, chlorophyll a, chlorophyll b, total chlorophyll content, soluble protein and catalase activity decreased with increase in salinity whereas, free proline, peroxidase activity and sugar content increased in all the genotypes. Seed cotton yield, total dry matter and leaf area at different stages of crop growth reduced with increase in salinitv. The higher mean salinity index, tolerance index and lower slope of regression for seed cotton yield and total dry matter at harvest in AK 235, LRA 5166, AK 84635 and Jayadhar indicated their suitability to salt stress conditions. Based on the study the genotypes AK 235, LRA 5166 and AK 84635 were found to be tolerant to salinity stress. Lesser reduction in germination, shoot and root vigour indices, photosynthetic rate, stomatal conductance, leaf area, total dry matter and chlorophyll content, maintenance of higher K/Na ratio and higher catalase and peroxidase activity at higher salinity levels can serve as selection criteria for identification of salinity tolerance at eariy stages of crop growth in cotton."