Grapevine Bunch Rots: Impacts on Wine Composition, Quality, and Potential Procedures for the Removal of Wine Faults

Abstract

Bunch rot of grape berries causes economic loss to grape and wine production worldwide. The organisms responsible are largely filamentous fungi, the most common of these being Botrytis cinerea (gray mold); however, there are a range of other fungi responsible for the rotting of grapes such as Aspergillus spp., Penicillium spp., and fungi found in subtropical climates (e.g., Colletotrichum spp. (ripe rot) and Greeneria uvicola (bitter rot)). A further group more commonly associated with diseases of the vegetative tissues of the vine can also infect grape berries (e.g., Botryosphaeriaceae, Phomopsis viticola ). The impact these fungi have on wine quality is poorly understood as are remedial practices in the winery to minimize wine faults. Compounds found in bunch rot affected grapes and wine are typically described as having mushroom, earthy odors and include geosmin, 2-methylisoborneol, 1-octen-3-ol, 2-octen-1-ol, fenchol, and fenchone. This review examines the current state of knowledge about bunch rot of grapes and how this plant disease complex affects wine chemistry. Current wine industry practices to minimize wine faults and gaps in our understanding of how grape bunch rot diseases affect wine production and quality are also identified.

Wine microbiome: A dynamic world of microbial interactions

“…They include filamentous fungi of the genera Aspergillus and Penicillium, which may greatly influence the hygienic characteristics or sensory quality of wine through the production of mycotoxins (aflatoxins, ochratoxin A and others) or off-flavors (such as geosmin, IPMP and 2-MIB), respectively (Steel et al, 2013;Rousseaux et al, 2014). Other microorganisms may also be present and responsible for diseases, such as downy mildew (Plasmopara viticola), powdery mildew (Erysiphe necator) and gray mold (Botrytis cinerea, which also generates off-flavors) (Kassemeyer & Berkelmann-Löhnertz, 2009;Steel et al, 2013).…”

Effects of Bunch Rot (Botrytis cinerea) and Powdery Mildew (Erysiphe necator) Fungal Diseases on Wine Aroma

“…This study focused on Botrytis cinerea and Erysiphe necator , since they are amongst the most relevant fungi in viticulture and have a world-wide impact on the wine industrial production (Dean et al, 2012; Steel et al, 2013). They are responsible for bunch rot and powdery mildew diseases, respectively.…”

“…They are responsible for bunch rot and powdery mildew diseases, respectively. Both fungi can affect grape berries, resulting in yield losses and reduced fruit quality depending on the degree of infection (Stummer et al, 2003, 2005; Calonnec et al, 2004; Steel et al, 2013). …”

“…Effects of bunch rot on wine quality are: (I) an altered carbohydrate metabolism leading to an increase in the amount of high molecular weight polysaccharides causing problems during processing; (II) an enhanced production of the oxidative enzyme laccase that has been shown to be related to a browning effect in wine color; (III) the generation of off-odors, and (IV) a reduction of the concentration of phenolic compounds, organic acids and varietal aromas (Ribéreau Gayon et al, 1980; Slomczynski et al, 1995; Ky et al, 2012; Steel et al, 2013). …”

Gray mold caused by Botrytis cinerea limits grape production in Chile

“…Notable textbooks (Coley-Smith et al, 1980; and review articles (Jacometti et al, 2010;Mundy, 2008;Romanazzi et al, 2012;Steel et al, 2013;van Kan et al, 2014;Williamson et al, 2007) have been published on the biology, epidemiology and control of the disease caused by B. cinerea. In this article, we reviewed numerous studies and discuss the factors that affect grape GM, as well as control strategies with special reference to the Chilean situation.…”