Water induces microcracks in the grape berry cuticle

Introduction: Bunch rots and berry cracking are major limitations in viticulture in humid climate that reduce yield and compromise quality of must and vine (MENEGUZZO et al. 2008). Microscopic cracks (microcracks) in the cuticular membrane (CM) play a critical role because they impair the barrier function of the CM in pathogen defense and water transport and function as stress concentrators that weaken the exocarp (CONSIDINE 1982). Microcracking of the CM occurs in many fruit crops and surface moisture on a strained CM is a critical factor in microcracking (KNOCHE and PESCHEL 2006). The CM of grape berries (Vitis vinifera L.) is strained (BECKER and KNOCHE 2012), too, and therefore, water on the surface is expected to aggravate microcracking also in grape berries. The objective of this study was to 1) characterize the distribution of microcracks on the berry and 2) establish the effect of water, temperature, and humidity on formation of microcracks in the cuticle of ‘Riesling’ berries.