Screening for Crown Gall Disease Resistance in Various Grapevine Cuttings Inoculated by Agrobacterium vitisC493 and C4612

Xia Xu, Jiang Lu, Jeong Ho Roh, Zhongbo Ren, Hong Huang

Abstract


Crown gall of grapevines is an important disease worldwide. In Florida, crown gall is commonly found in grapes, apples, peaches, raspberries, and roses. This condition reduces vine vigor and causes substantial economic loss for growers and nurseries. In this experiment, we screened 6- to 7-year-old green (June) and dormant cuttings (December) of 29 commercially available muscadine grape cultivars (Vitis rotundifolia), five European bunch grapes (V. vinifera), and five Florida hybrid bunch grapes, and two French-American hybrids, and Shuttlewuthii sp. by inoculating with AgrobacteriaC493 and C4612. Cuttings without inoculation and cuttings inoculated with sterilized distilled water were used as controls. Gall incident rate and gall weight were scored at inoculated sites and top sites of the cuttings 2 months after the inoculation. All the green cuttings from muscadine grape cultivars showed about 0.1 to 0.2 g callus/gall growth (abnormal overgrowth) in the inoculated sites for both C493 and C4612. Higher levels of abnormal overgrowth were found on cuttings inoculated with C4612. However, only inoculated cuttings from V. viniferaand Florida hybrid bunch grapes showed callus/gall growth ranging from about 0.2 to 0.3 g at inoculated sites with C493 or C4612. No callus/gall growth was noticed for controls. Scanning electron micrographic analysis of the growth tissue found the presence of bacteria in inoculated ones but not in controls for all cultivars screened. The results indicated that muscadine grape was not completely immunized to crown gall disease and pathogen C4612 was more virulent than C493.

Keywords


bunch grapes, muscadine grapes, plant disease resistance

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Proc. Fla. State Hort. Soc.     ISSN 0886-7283