FIELD EVALUATION OF GRAPE ROOTSTOCK RESPONSE TO NATURAL INFECTION BY PIERCES DISEASE

• Author(s): Cousins, Peter; Lu, Jiang; Ren, Zhongbo;
• Abstract: To understand the adaptation of grape rootstocks commonly used in major grape production areas worldwide to Florida, where Pierces dsease (PD) is the primary limiting factor in grape production, ten important grape rootstocks were cultivated at the experimental vineyard, Florida A&M University, Tallahassee, Florida. Disease resistance and symptoms and growing performance were evaluated. PD symptoms were scored in September and October 2002 and 2003, with leaf symptoms the basis of scoring. None of the grape rootstocks was completely resistant to PD and the severity of PD varied with rootstock cultivar. Ramsey and St George showed least PD symptoms, while Freedom and 3309C had the highest PD scores. Vine vigor was evaluated in the fall of 2002 and 2003, and varied among the rootstocks as evidenced by trunk diameter, annual shoot length, annual shoot node number, internode length, and shoot diameter. Shoot death rate in 2002 ranged from 7% to 56%, with Freedom the highest and O39-16 the lowest. The overall growth performance suggested that St George and Ramsey are the most suitable rootstocks in northern Florida environment where natural infection by PD is very high and vectors and inoculum are abundant.
• Publication Date: Aug 2003
• Journal: 2003 Pierce's Disease Research Symposium