Drought Stress Responses of Wheat Genotypes with respect to Nutritional Quality

Effect of post-anthesis drought stresses on photosynthesis (in terms of chlorophyll content) and subsequent impact on starch accumulation in grain, micronutrients and phytic acid composition along with seed test weight was investigated in different drought tolerant wheat varieties viz. RSP-566, RSP-561, PBW-396, HD-2687, C-306, PBW-175, RSP-81, PBW-550, DBW17 and WH-542. Leaf chlorophyll content, 100 seed test weight and grain starch content was found to decay under all moisture stress conditions (10, 17, 24 days after anthesis) and decay pattern of these parameters with respect to wheat genotype was similar. Chlorophyll and starch under irrigated condition recorded highest values in HD-2687 and seed weight in PBW-175 but PBW-175 was able to sustain comparatively high values in all parameters, whereas HD-2687 showed low values with high reduction percent with days of water stress. However, RSP-561 and PBW-396 followed PBW-175 in decay trends of the parameters. Calcium, phosphorus, iron, zinc and phytic acid under control condition varied intergenotypically raging from 25.42 -76.67, 41.57–63.94, 3.82 -4.45, 2.50 -3.95 mg/100g and 0.33 -1.66 g/100g, respectively. Water deficiency caused a gradual and significant rise in all these parameters with highest values at 24 days stress. However, calcium level was found to enhance up to 17 days of stress but a down fall started afterwards and minimum value was recorded at 24 days of stress. RSP-561 showed highest potency in micronutrient quality possessing highest zinc and second highest iron and calcium compositions with lowest level of phytic acid at all degree of moisture deficiency. However, RSP-566, PBW-396 and PBW-550 showed medium potency with highest efficacy in iron, calcium and phosphorus content respectively and low to moderate phytic acid levels at all stages including irrigated condition. Comparison of different doses of moisture deficiency revealed that 10 days stress improved micronutrient composition to a good extent with little increase of phytic acid and small decay of starch composition in grain. Hence 10 days moisture stress at post-anthesis may be considered as assistance factor for improving nutritional quality in general for all wheat genotypes and especially for drought tolerant genotypes where starch reduction was comparatively low. The genotype RSP-561 which had highest starch (66.57%), calcium, phosphorus, iron, zinc (75.50, 56.0, 4.94 and 4.06 mg/100g, respectively) and phytic acid (0.40g/100 g) at 10 days drought stress was considered best sustainable genotype having highest nutritional quality.