Nutritional Aspects of Grape (<i>Vitis vinifera</i> L.) Clusters Afflicted with SOUR Shrivel Is Related to Functionality of Its Vascular Tissues

Abstract

Mineral nutrition is essential to growth and development of various plant organs including fruits; consequently deficiency of any element leads to a myriad of physiological disorders, which in fruits are manifested as ripening anomalies. In this study, nutritional composition in tandem with vascular structure of healthy grape clusters and clusters afflicted with SOUR shrivel, a ripening disorder has been examined to unravel its mechanistic basis. The healthy berries without any affliction accumulated the highest amounts of all nutrients, which paralleled with functional xylem and phloem tissues in their cluster framework. Among the macro nutrients, K occurred as the dominant element followed by P, Ca, Mg and S whereas B was the predominant micro nutrient followed by Fe, Cu, and Zn. Although, the SOUR shrivel berries and the healthy appearing berries of afflicted clusters followed similar accumulation patterns, their amounts were significantly lower than the perfectly healthy berries without any SOUR shrivel. The low nutrient levels of SOUR shrivel berries corresponded to necrosis of phloem tissues and a red discoloration of xylem tissues in their cluster framework indicating that a lack of functional vascular tissues provoked the induction of SOUR shrivel by reducing influx of xylem and phloem mobile nutrients into the afflicted berries. Hence, periodic nutritional checks starting before veraison may aid in curbing the incidence of SOUR shriveling.