Characterization of wheat (Triticum aestivum) genotypes on the basis of metabolic changes associated with water stress*

Drought stress responses in cross bred wheat genotypes, viz RSP 561, RSP 566, RSP 529, RSP 564, RSP 511 and RSP 560 was studied by measuring the changes in osmolytes and cell protecting biochemicals, viz proline, reducing sugar, free amino acid, total polyphenol, antioxidant, superoxide dismutase (SOD), catalase and peroxidase (POD) along with relative water content (RWC) from the leaves samples after induction of water stress at flowering stages. National wheat cultivars, PBW 175 recognized as drought resistant and PBW 343 susceptible, were taken as references. It was recorded that all the parameters under water stress except relative water content increased significantly in all the wheat genotypes. The inter-genotypic variation of proline, reducing sugar, free amino acid, total polyphenol, antioxidant, SOD, catalase and peroxidase levels in controls ranged from 1.09_ 2.70 mmole/g, 0.48_0.96%, 0.68_1.13%, 11.51_24.40 mg/ g, 5.43_36.51%, 27.35_ 72.95 mM H2O2/min/100 mg, 151.85_172.10 unit/min/100 mg and 130.71_158.92 unit/ min/100 mg and the raised levels ranged from 6.07_14.96 mmole/g, 1.93_ 3.92%, 2.02_4.41%, 15.33_ 28.38 mg/g, 10.76_44.51%, 32.59_98.66 mM H2 O2/min/100 mg, 170.64_ 210.72 unit/min/100 mg, 168.8_186.78 unit/min/100 mg respectively, whereas the RWC decreased from 58.33_ 80.68% to 47.06_61.71%. The wheat genotypes RSP 564 and RSP 529 carried significantly high values of proline, free amino acid, reducing sugar, total polyphenols, antioxidant content and detoxicating enzymes SOD, catalase and POD activities both in control and water stress conditions along with maximum leaf water retention and hence can be considered highly tolerant to water stress, followed by national cultivar PBW 175 with the values in the third position in order. PBW 343 though possessed high values in total polyphenol, antioxidant and detoxicating enzymes but showed very low values in osmolytes and RWC and can be assessed low tolerant to water stress. RSP 566 which showed lowest values in most of these parameters can be elucidated as drought stress susceptible genotype.