GRAPE

GRAPE

Grapevine is one of the oldest known crops to mankind. The Vitis vinifera species is native to the Mediterranean region, central Europe and southwestern Asia – from Morocco to northern Iran, and from Portugal north to southern Germany.

More than 80 % of the harvested grapes are used in wine production worldwide. At least 74.5 million metric tons of grapes were commercially harvested globally in 2014 from more than 7 million hectares of vineyards(source: FaoStat).

GRAPE DISEASES

Downy mildew is the most important key pathogen worldwide in vineyards. This pathogen has sexual and asexual spores and this trait strongly influences the epidemiological behaviour, which is chracterized by primary (sexual) and secondary (asexual) infection cycles that overlap for a part of the season.

Powdery mildew is the most important grapevine pathogen in epidemiological perspective. The fungus can infect all green tissues on the grapevine but causes the most damage to leaves and berries (Caffi et. al., 2011). The impact powdery mildew infection has on a vineyard often depends on the timing of the first infection. Early fruit infections cause stunted berries, scarring, and off-flavors in wine. Powdery mildew also reduces the storage life of table grapes and can affect the rate of photosynthesis, thus reducing berry sugar content.

Phomopsis cane and leaf spot on grapevine is caused by the fungus Phomopsis viticola. It develops during a wet springtime when spores are spread by rain splash. Cool wet weather and prolonged leaf wetness increase the appearance and severity of Phomopsis symptoms. Crop loss occurs as a result of girdling at the base of shoots, weakening and cracking of canes, which results in lower vine productivity. Yield loss can also occur due to infection of the bunch stems and from berry rot. Fungicides registered for use against Phomopsis are not effective if applied after the disease symptoms have appeared.

This disease is significant for causing the rot of grape berries and clusters. All cultivated varieties of grapes are susceptible to infection from black rot fungus. The extent of crop failure is influenced by weather factors. The start of infection and the time period of incubation depends on leaf wetness, relative humidity and average air temperature. A film of water on the vine surface is necessary for infection.

Botrytis cinerea is a very significant pathogen in wine grapes. The disease regularly occurs in vineyard, the most critical stages for B. cinerea infection are flowering and the period between berry ripening and harvest. The pathogen colonizes senescent floral parts (stamens and calyptras) persisting in latent forms in bunches, and therefore providing the necessary inoculum for late infections during the maturation stage. The extent of crop failure is mainly influenced by weather factors (precipitation, relative humidity and daily air temperature).

Rotbrenner or red fire of grape, caused by Pseudopezicula tracheiphila, is a significant grape disease in the cooler viticultural growing regions of Europe. The pathogen can overwinter in dead leaves on the ground, and in early spring the ascospores are discharged and they can infect the new season’s shoots. Heavy rainfall and prolonged wetting periods favour pathogen spread and infection.

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