Xanthomonas ampelina . [Descriptions of Fungi and Bacteria

Abstract

Abstract A description is provided for Xanthomonas ampelina . Information is included on the disease caused by the organism, its transmission, geographical distribution, and hosts. HOSTS: On Vitis vinifera . DISEASE: Bacterial blight of the grapevine, 'Tsilik marasi' in Greece; 'Maladie d'Oleron' in France, 'Vlamsiekte' in South Africa. In early spring, buds on infected spurs fail to open or make stunted growth which eventually dies. Affected spurs often appear slightly swollen because of hyperplasia of the cambial tissue. Cracks appear along such spurs, become deeper and longer, forming cankers. Young shoots may develop pale yellowish-green spots on the lowest internodes. These expand upwards on the shoot, darken, crack and develop into cankers. Cracks and, later, cankers also form on more woody branches later in spring. In summer, cankers are often seen on the sides of petioles, causing a characteristic one-sided necrosis of the leaf. They may also appear on main and secondary flower and fruit stalks. Leaf spots and marginal necrosis occur sometimes. Gum formation is not necessarily a symptom. GEOGRAPHICAL DISTRIBUTION: Greece, France and South Africa (51, 551). The symptoms have been reported from other countries and attributed to Erwinia vitivora , which is now thought to be synonymous with E. herbicola (CMI Descript. 232). Such reports have come from Italy, Sicily, Spain, Portugal, Switzerland, Austria, Yugoslavia, Bulgaria, Tunisia, Canary Islands and Argentina (31, 105; Du Plessis, 1940; Panagopoulos, 1969). Many of these records are almost certainly of X. ampelina . TRANSMISSION: Most information is based on observational data rather than on experiments. Bacteria overwinter in the vines, emerge, probably in spring and are carried to healthy shoots, most probably in wind and rain. Wounds may facilitate entry but are not needed for primary infection. Considerable spread can occur in propagating material, by grafting and by pruning knives. More knowledge should be gained now that the true pathogen is known.