DROUGHT TOLERANCE IN WHEAT

Abstract

In coming times, climatic fluctuations (water scarcity, temperature extremes etc.) and population growth will trigger multiple challenges, most sensitive being food security. Field crops are at serious risk of acute climatic conditions during growth period; most detrimental is drought stress that affects all stages (seedling, vegetative and reproductive stage) of plant growth and development. Annually, 17-70% yield losses are reported in Pakistan due to water shortage. Cereals especially wheat, the staple food for almost 35% of world population and 60% of the daily diet of common man in Pakistan with average per capita consumption of 125 Kg,is highly sensitive to drought. However, wheat crop has developed multiple physiological mechanisms that facilitate them to acclimatize water scarcity and this mechanism may vary among diverse genotypes. A study was designed in cemented tanks (3mx3mx1m) under controlled environment in wire netted pot house as well as under field conditions, to evaluate drought tolerant wheat genotypes collected from plant breeding & genetics division (PBGD) of Nuclear Institute of Agriculture (NIA) Tando jam. The experiment was arranged in completely randomized design (CRD) while field experiment was arranged in randomized complete block design (RCBD) with two treatments i.e. Control (well-watered) and drought (only soaking dose), and replicated thrice. The genotypes were evaluated on the basis of physiological indices, i.e.relative water contents (RWC) chlorophyll contents, potassium accumulation, osmotic potential, nitrate reductase activity and proline (amino acid) accumulation. Generally, differential responses in terms of physiological indices and grain yield were observed. However, potential genotypes (AST-I (V₁), A₂ and SDW-2) showed better performance under drought compared with control. A 4-5 fold increase in the proline content was observed in potential germplasm.On the basis of <50 % reduction in grain yield (7.0-7.4 g plant^-1) under drought and physiological indices (RWC, chlorophyll, nitrate reductase activity, proline accumulation, Potassium and osmotic potential), three genotypes, viz. AST-I(V₁), A₂ and SDW-2 may be considered as having more drought tolerance potential as compared to other genotypes. The drought tolerant genotypes specified in this study may be recommended to wheat breeders to produce stress tolerant genotype.