Frequent Foliar Sprayings of Salicylic Acid with Elevated Concentrations Enhance Growth, Yield and Fruit Quality of Strawberry (Fragaria x ananassa Duch. cv. Festival) Plants

Abstract

Salicylic acid regulates several physiological and biochemical processes in plants. The previous studies on strawberry used salicylic acid with low concentrations varied from 0.5 mM to 2.0 mM which was sprayed once, twice or thrice. The highest concentrations of salicylic acid with the maximum times of applications gave the highest values of growth and yield parameters. To study the effect of frequent foliar sprayings of salicylic acid with elevated concentrations (0.0, 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, or 7.0 mM) applied every 10days during all the growth stages of strawberry cv. Festival plants, a field experiment was conducted during 2013/2014 and 2014/2015 seasons at the Experimental Farm of Horticulture Department, Faculty of Agriculture, Ain Shams University, Qalubia Governorate, Egypt. Compared with the water-sprayed plants, salicylic acid spraying up to 5.0 mM had positive and significant effects on the vegetative growth parameters, leaf SPAD readings, leaf relative water content, leaf membrane stability index, leaf content of macronutrients, number of fruits/plant, early and total yields/plant, and fruit soluble solids content. Salicylic acid at 4.0 mM gave the highest significant values of the aforementioned parameters. Moreover, increasing salicylic acid concentrations significantly reduced nitrate content in the fruits. In addition, a comparative microscopic examination showed that salicylic acid at 4.0 mM increased the cell thickness of both upper and lower epidermis, and the thicknesses of palisade and spongy tissues. Salicylic acid spraying at 4.0 could offer an economic, rapid, applicable, and effective way for enhancing growth, yield and fruit quality of strawberry cv. Festival.