Biochemical Characterization and Molecular Variability Associated with Drought Tolerance in Cotton

Thirty cotton genotypes (5 Gossypium arboreum and 25 Gossypium hirsutum) were analyzed for biochemical characters related to drought tolerance. Genotypes, JDRL-1, JDRL-2, JDRL-3, JDRL-4, JDRL-5 (G. arboreum) and JDRL-6 (G. hirsutum) were found to be highly drought tolerant based on relative water content (RWC) under stress condition. However, JDSL-24 (G. hirsutum) was recorded highly drought susceptible. Among biochemical parameters, soluble proteins correlated positively against drought tolerance (RWC) followed by proline and glycine betaine content. Leaf soluble proteins (15.35 mg×g⁻¹fr.wt.), proline content (0.20 mg×g⁻¹fr.wt.) and glycine betaine content (9.64 mg×g⁻¹fr.wt.) was recorded highest in drought tolerant genotype JDRL-1 while free amino acids (0.470 mg×g⁻¹fr.wt.) were elevated in JDRL-3. Total 20 RAPD primers were used to generate 198 bands in which 188 bands were polymorphic with an average of 9.4 bands per primer and total six RAPD primers [CPA-11_{(2738, 672, 376)}, OPA-2₍₅₀₂₎, OPE-08_{(4375, 3724, 488)}, OPM-06₍₄₀₇₎, OPO-09_{(2726, 2102)} and OPZ-15_{(2211, 1124, 276)}] amplified shared unique fragments between all five highly drought tolerantG. arboreum and two tolerant G. hirsutum genotypes JDRL-6 and JDRL-15. Dendrogram constructed from the RAPD data showed that JDRL-4 genotype of cotton was the most diversified genotype observed having separate position in cluster-II. The leaf osmolytes glycine betaine, soluble proteins, free amino acid and free proline were the effective biochemical markers to screen the cotton genotypes suitable for drought condition.