SALICYLIC ACID MEDIATED HEAT STRESS TOLERANCE IN SELECTED BREAD WHEAT GENOTYPES OF PAKISTAN

Wheat is one of the most important cereal crop significantly affected by continual and terminal heat stress. Phytohormones are recognized as a strong tool for sustarnably alleviating adverse effects of abiotic stress in crop plants. The impact of externally applied salicylic acid was investigated on physiological and agronomical traits of five wheat varieties under heat stress in pot and field study. Salicylic acid was applied exogenously through two ways: 1) pre-soakmg seeds in 10(-4)M solution of salicylic acid for 24 hours, and 2) foliar application of salicylic acid to the adult wheat plants three days prior to heat stress, while untreated seeds were used as control. In pots, high temperature stress was imposed to plants at post anthesis stage, whereas, in field study one set was sown late so that plants can receive high temperature at gram filling stage. Both field and pot study revealed that heat stress reduced the gram yield and thousand kernel weights. Heat stress reduced leaf chlorophyll content by 34% and brought about an increase of 40% in proline content, 20% in leaf soluble proteins and 17% in soluble sugars as compared to the control plants. Application of salicylic acid through seed treatment and foliar application increased the chlorophyll content in leaves by 18% and 24%, enhanced soluble protein by 21%, proline by 40% and 47% and sugar accumulation by 81% and 88% respectively, and enhanced the net yield by 19% in pot experiment and by 13% in field expenment in selected wheat genotypes of Pakistan under heat stress. Based on results, it can be concluded that exogenous application of salicylic acid through seed priming or foliar spray led to stimulate heat stress tolerance in local wheat genotypes.