Phomopsis cane and leaf spot occurs wherever grapes are grown. Phomopsis cane and leaf spot is more severe in grape-growing regions characterized by a humid temperate climate through the growing season. Crop losses up to 30% have been reported to be caused by Phomopsis cane and leaf spot.Úrbez-Torres, J. R., Peduto, F., Smith, R. J., and Gubler, W. D. 2013. Phomopsis dieback: A grapevine trunk disease caused by Phomopsis viticola in California. Plant Dis. 97:1571–1579.

Hosts and symptoms

Phomopsis cane and leaf spot is a disease that causes symptoms in the common grapevine species, ''Vitis vinifera'', in many regions of the world. This disease is mainly caused by the fungal pathogen, ''Phomopsis viticola'', and is known to affect many cultivars of table grapes, such as Thompson Seedless, Red Globe, and Flame Seedless. Also in vines of oenological interest, such as Cabernet Sauvignon, Zinfandel, Syrah, Barbera, Chardonnay and Merlot. Spots or lesions on shoots and leaves are common symptoms of the disease. Small, black spots on the internodes at the base of developing shoots are probably the most common disease symptom. These spots are usually found on the first three to four basal internodes. The spots may develop into elliptical lesions that may grow together to form irregular, black, crusty areas. Under severe conditions, shoots may split and form longitudinal cracks. Although cane lesions often appear to result in little damage to the vines, it is important to remember that these lesions are the primary source of overwintering inoculum for the next growing season. Leaf infections first appear as small, light-green spots with irregular, occasionally star-shaped margins. Usually only the lower one to four leaves on a shoot are affected. In time, the spots become larger, turn black, and have a yellow margin . Leaves become distorted and die if large numbers of lesions develop. Infections of leaf petioles may cause leaves to turn yellow and fall off. All parts of the

grape cluster In viticulture, the grape cluster (also bunch of grapes) is a fertilized inflorescence of the grapevine, the primary part of this plant used for food (grape leaves are also used in some culinary traditions). The size of the grape bunch greatly va ...

(berries and rachises or cluster stems) are susceptible to infection throughout the growing season; however, most infections appear to occur early in the growing season. Lesions developing on the first one or two cluster stems (rachises) on a shoot may result in premature withering of the cluster stem. Infected clusters that survive until harvest often produce infected or poor-quality fruit. Soil moisture and temperature can impact the severity of symptoms, leading to a systemic infection in warm and wet conditions.

Disease cycle

Phomopsis cane and leaf spot is caused by an ascomycete fungal plant pathogen. This pathogen produces sexual spores (ascospores) in the teleomorph stage and asexual spores (conidia) during the anamorph stage. ''Phomopsis'' (Sacc.) Bubák (teleomorph: ''Diaporthe Nitschke'') is a cosmopolitan fungal genus that contains both plant pathogens and endophytes described from a wide range of annual and perennial hosts, including economically important crops. Úrbez-Torres, J. R., Peduto, F., Smith, R. J., and Gubler, W. D. 2013. Phomopsis dieback: A grapevine trunk disease caused by Phomopsis viticola in California. Plant Dis. 97:1571–1579. The teleomorph stage of the disease cycle does not occur in nature and involves sexual combination of the antheridium with the

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