Exogenous application of cytokinin (6-BAP) ameliorates the adverse effect of combined drought and high temperature stress in wheat seedling

Abstract

Drought and high temperature stress often occur simultaneously especially in rainfed grown wheat crop causing severe yield loss in most of the wheat growing areas of the world. The simultaneous effects of these two stresses on crop performance in terms of growth and development may be quite different than the individual stress, but there are limited studies on this topic. Drought as well high temperature stress inhibits CK synthesis and accelerates CK degradation, reducing CK levels in roots and shoots. Experiments were performed in 10 days old wheat seedling under independent and combined drought and high temperature stress conditions with two contrasting set of wheat genotypes (C-306, tolerant and Ko-307, susceptible). Combined stress significantly reduced the membrane stability, RWC, CSI and photosynthetic pigments contents and increased the lipid peroxidation (TBARS contents). While exogenous application of optimize dose of 10 ppm BAP, (identified in preliminary experiments based on changes in growth and physiological traits) significant increased membrane stability index (MSI), photosynthetic pigments contents, chlorophyll stability index and RWC and other growth parameters in wheat seedlings grown under independent and combined stress conditions. However, genotypes subjected to drought, high temperature & combined drought and high temperature stress in 10 days old wheat seedlings. Overall it is concluded that, combined effect of drought + high temperature stress was more detrimental than the individual stress however, the interaction effect was hypo-additive in nature, which may be due to cross adaptation effect and further exogenous application of cytokinin (6-BAP) ameliorates the adverse effect of combined stress as well individual stress.