'Dog Ridge/ A Superior Grape Rootstock for Florida

Two rootstock trials, one involving 5 and the other 6 scion cultivars were conducted at Leesburg between 1963 and 1971. 'Dog Ridge' was superior to 4 other rootstocks in soil prev iously planted with grapes and to 10 other rootstocks in soil not previously in grapes. Scions grafted on 'Dog Ridge' had greater fruit produc tion, trunk circumference, and shoot vigor than the same scions grafted on other rootstocks. 'Dog Ridge' cuttings rooted well and grew vigorously in the nursery. It was compatible with all scion cultivars grafted on it and the percentage of suc cessful unions was high. 'Dog Ridge' is resistant to Pierce's disease and parasitic nematodes, but is susceptible to rust and to freeze damage occurring before onset of dormancy. Use of rootstocks for grapes in Florida dates back to 1889, when Neal (12) described a heavy incidence of root-knot on Vitis vinifera L. and V. aestivalis Michx. By grafting to native species such as V. cordifolia Michx, he obtained superb growth free of root-knot. Clones of V. champini Planch, native to Texas were selected before 1900 by Munson and used as rootstocks (11). One of his most outstanding V. champini cultivars was 'Dog Ridge/ later proven to be resistant to Pierce's disease (7) and to parasitic nematodes (3, 4). 'Dog Ridge' was outstanding in rootstock tests in several states (2, 3, 4, 5, 6, 8, 9); however, in Florida decline and death of cultivars grafted on V. champini occurred after only 2 years of vigorous scion growth (5). By contrast, 'Lake Emerald* has made vigorous growth as a replant in Florida vineyards (13) and merits testing as a rootstock. The purpose of this research was to compare the performance of 'Dog Ridge' with that of other rootstocks at the Agricultural Research Center, Leesburg, and to explain the previous failure of 'Dog Ridge' in Florida. Florida Agricultural Experiment Station Journal Series No. 4664. Materials and Methods In order to test rootstocks on soil previously planted with grapes, 5 rows of 5-year-old vines were removed in 1963, and the same rows were planted with 5 different rootstocks: 'Dog Ridge' (Vitis champini), 'Black Spanish' (V. bourquiniana Munson) 'Lake Emerald' (V. simpsoni Munson cv. 'Pixiola' x 'Golden Muscat'), W380 (sister of 'Lake Emerald'), and W1521 ((V. smalliana Bailey x V. lincecumi Buckley) x 'Lake Emerald'). All except 'Black Spanish' were grafted in 1964 with 5 different scions in 2 replications (1 plant each): 'Norris,' 'Stover,' 'Blue Lake,' FES A3-34, and FES A3-60. 'Black Spanish' was not grafted until 1966 because of slow growth. Two rooted cuttings of each of the 5 scion culti vars were planted in the same rows for comparison. On land not previously cropped with grapes, a 90-plant rootstock test was planted in December 1964. The original planting included the following rootstocks: 15 plants each of 'Lake Emerald' and W380; 6 plants each of Meyer 56-153-2, 'Dog Ridge,' A4-62, 'Black Spanish,' 3309 (V. riparia Michx. x V. rupestris Scheele), C5-24, 'Duval' (V. simpsoni) (4 plants, plus 2 plants of Al-32), Fla. 449 (V. smalliana x V. lincecumi), 'Mantey' (V. shuttleworthi House), and 'Norris. ' Three of the rootstocks were discarded after 1965: Meyer 56-153-2 (poor graft unions); A4-62 and 3309 (poor vigor). In their places were set 6 plants each of USDA 22, C4-46, and D7-4. Also, 6 plants of W380 were replaced by D4-133 in order to test the latter. Each rootstock cultivar was grafted in February 1966 with 6 different scions: D2-136, D3-79, D4-176, D5-10, D5-164, and D5-167. Data on vine vigor, fruit yield, trunk circum ference, and weight of prunings were recorded from date of planting until 1971. Results and Discussion In land previously planted with grapes, scions on 'Dog Ridge' had the highest fruit yield over a 6-year period (Table 1), and also the most years when more than 5.5 lb. of fruit per vine (2 tons per acre) was harvested (Table 2). Scions on 'Dog Ridge' were also the most vigorous as meas ured by the number of years in a 7-year period when prunings exceeded 2 lb. (Table 2). Replant276 FLORIDA STATE HORTICULTURAL SOCIETY, 1972 Table 1. Mean fruit yields (lb per vine) for a 6-year period in a rootstock test in old vineyard soil (1966-1971)