Effect ‎ of foliar application of Zinc and exogenous application of proline on yield ‎and grain Zn and P content in a wheat durum cultivar Saji under drought stress ‎condition

Introduction:

  Heat and dry stress events during the wheat-growing season, particularly during wheat grain filling, are among the prevalent environmental constraints that adversely affect wheat growth and productivity worldwide. Because people in developing countries are highly dependent on cereal-based diets, they are prone to Zn-related diseases. The situation becomes worse when the crop is grown in soil with low Zn content. Studies have shown that the application of Zinc (Zn) successfully increased wheat grain yield and grain Zn content and improved wheat tolerance to drought. The present studies are designed to provide a better understanding and further information on the response of wheat to Zn application under drought conditions. 

 The present study included two experiments: a preliminary experiment that aimed to elucidate the effect of the application of Zn via foliar or seed priming on wheat tolerance to drought stress and a field study that was designed to investigate the effect of exogenous proline and foliar application of Z on wheat yield and grain nutrient. A preliminary experiment detected the effects of the Zn application method on the biochemical and molecular characteristics of drought-stressed wheat. Proline-biosynthesis-related gene [Δ1-pyrroline-5-‎carboxylate reductase (P5CS)] expression, proline accumulation, and malondialdehyde content were determined four days after drought stress was imposed. A subsequent field experiment (Experiment 2) was also conducted to elucidate the effect of foliar application of Zn [0, 0.1, 0.2 and 0.3% (w/v)] individually and in all possible combinations with proline (0 and 15 µ mole) on wheat performance under post-anthesis drought stress condition. The foliar application was applied at anthesis. All plants were exposed to drought stress by withholding irrigation for 21 days. The field experiment was conducted in 2021/22 during the wheat-growing season at a commercial wheat-grown farm. The experiment site is located in Sirvan County, Ilam Province. A durum wheat cultivar, ‘Saji’, was used in both experiments. Result: Zn application, mainly when applied via foliar, increased P5CS mRNA accumulation and proline content and decreased malondialdehyde content in the leaf compared to the control treatment.

Results:

 of the field experiment showed that the combined application of Zn and proline successfully biofortified field wheat with Zn and could ameliorate the adverse effect of post-anthesis drought stress. Under field conditions and compared with the control plant, treated plants with 0.1%, 0.2%, and 0.3% ‎(w/v‎)‎ of ZnSO4.7H2O solution significantly increased grain yield by 1.7%, 7.24%, and 3.62%, respectively. Compared with the control treatment, exogenously applied proline increased grain yield by up to 4.4%. Results showed that the foliar application of Zn at 0.2% (w/v) in combination with proline (15 mM) had a more significant effect on increased grain yield. Foliar-applied Zn at 0.1%, 0.2% and 0.3% ‎(w/v‎)‎ of ZnSO4 solution decreased grain P content by 8.3%, 14.7% and 18.1%, respectively, as compared with the control. Foliar Zn application of 0.1%, 0.2%, and 0.3% ‎(w/v‎)‎ of ZnSO4.7H2O solution increased Zn content in grain by 6.3%, 11.9%, and 19.1%, respectively, to control plants.

 Regarding the cost for farmers, foliar application of Zn at a concentration of 0.3% at the anthesis stage can be suggested as the best treatment to improve both the quantity and quality of wheat.