Sophorolipid Surfactant-Mediated Green Synthesis and Characterization of Zinc Oxide Nanoparticles for Abrogating Zinc Deficiency in Wheat (Triticum aestivum L.) Crop

The study focuses on biosurfactant-mediated green synthesis of zinc oxide nanoparticles (ZnO NPs) for foliar application in wheat (Triticum aestivum L.) crop to mitigate zinc deficiency. The sophorolipid biosurfactant BS32 [0.5% (w/v)] produced by yeast Meyerozyma guilliermondii YK32, acted as a reducing and stabilizing agent during the synthesis of ZnO NPs. The nanoparticles (NPs) exhibited a spherical morphology and hexagonal wurtzite structure, with an average particle size of 19.45 nm. These were non-phytotoxic towards seed germination and compatible with bioinoculants of wheat, Azotobacter chroococcum Mac 27 and Pseudomonas strain P36. The foliar spray of NPs (150 ppm) in zinc deficient (WH 1105) and fortified (WH 1063) wheat varieties enhanced total chlorophyll content by 23.2% and 28.2% and plant height by 18.2% and 20.5%, respectively over control plants. The NP foliar spray in WH 1105 and WH 1063 viz-a-viz control (T3) increased grain weight per plant from 0.895 to 1.530 g and 0.714 to 1.074 g while increasing the percent grain zinc content by 37.46 and 32.34%, correspondingly. The ZnO NPs at 150 ppm were stimulatory to the growth, yield and grain quality of the wheat crop and, therefore, could be suggested as a source of zinc after affirmation of the findings under field conditions.