Rootstock Interaction with Cultural Practices

of rootstock affected total vegetative growth and higher pruning formulae resulted in reduced shoot vigor on all rootstocks. Total leaf area per vine averaged 28.1, 16.7, 14.6, 11.0, 9.6, and 4.2 m2 on 1103P, 110R, 3309C, S04, 101-14, and 420A respectively. Shoot lengths averaged 150, 120, 98, and 84 cm at the 4, 8, 12, and 16 bud formulae. Under the extreme pruning formulae and rootstock capacities used in this study, rootstock/pruning interactions were noted for all aspects of vegetative growth except final pruning weight. At low pruning formulae, higher capacity rootstocks produced larger shoots (176cm on 1103P and 110R compared to 118 cm on 420A). Differences in vigor diminished at higher pruning formulae. Total vegetative growth responded curvilinearly to pruning. Leaf area per vine was reduced by 40%at the lowest pruning formula on all rootstocks except 110R. For all rootstocks, it reached a maximum between the 8 and 12 bud/lb formulae and declined slightly thereafter. Rootstock affected yields both through effects on initial vine size and through effects on bud fruitfulness. Yields averaged 13.7, 9.0, 7.2, 4.4, 5.5, and 1.9 per vine for 1103P, 110R, 3309c, SO4, 101-14, and 420A respectively. Larger vines also produced larger clusters with more and larger berries. Cluster weights averaged 105, 101, 93, 88, 94, and 72 gm for 1103P, 110R, 3309c, SO4, 101-14, and 420A, respectively. The number of clusters per shoot varied by rootstock but was less dependent on vine size, averaging 1.79, 1.86, 1.68, 1.68, 1.86, and 1.60 clusters per shoot for 110R, 101-14, 1103P, 3309C, SO4, and 420A. Significant pruning/rootstock interactions existed due to very low fruitfulness on lowest capacity rootstock at the lowest pruning formula. Rootstock and pruning formula affected crop to pruning weight ratio without significant interaction. Crop to prunings ratios were lower on SO4 and 420A than on other rootstocks (3.5, 3.6, 4.8, 5.1, 5.4, and 5.5 on SO4, 420A, 3309C, 101.14, 110R, and 1103P). Crop to pruning weight ratios increased from 2.5 at the 4bud/lb pruning treatment to 6.3 at 16 bud/lb. Significant effects of rootstock, pruning formula, and their interaction were noted for rate of maturation. °Brix on 1103P was delayed at all pruning levels. Fruit from vines on 420A and SO4 was riper than that of vines on 110R, 309C or 101-14. Rootstock, pruning, and their interaction affected maturity solely through differences in crop and vegetative growth.

The independence of rootstock and pruning on vigor was found to break down at extreme capacities and pruning formulae. Further, the response of total vegetative growth to pruning was found to be curvilinear across the broader range of pruning formulae.

Total vegetative growth was dependent on pruning level and vine spacing. Pruning weights declined slightly from 0.9 kg/vine at 3 and 6 bud/m2 to 0.7 kg/vine at 9 bud/m2. Pruning weights increased from 0.65 kg/vine on 1M spacing to 1.2 kg/vine at 2.2m. Vigor was dependent on rootstock, pruning level and vine space. In all cases shoot growth fell to inadequate levels (below 30 gm/shoot) at the highest pruning level of 9 bud/m2. Yields were dependent on rootstock, pruning level, and vine space. With fewer clusters per shoot and setting fewer berries per cluster, 101-14 was less fruitful than 110R. Yields averaged 4.3 and 5.4 kg/vine on 101-14 and 110R respectively. Yields on 5-C were comparable to those of 110R. Yields were dependent on vine space and pruning level through number of shoots retained but reached a maximum at the 6 bud/m2 pruning level due to reductions in clusters per shoot and berry weight. At pruning levels of 3, 6, and 9 bud/m, yields were 1.5, 3.5, and 3.4 kg/vine on 1M vine spacing and 4.6, 7.5, and 7.4 kg/vine on 2m spacing. The balance of crop to vegetative growth depended solely on pruning level. Crop to pruning weight ratios were 3.9, 6.6, and 9.2 for the 3, 6, and 9 bud/m2 treatments. Rootstock and vine spacing had no effect on fruit composition at harvest. Maturities depended on pruning level without significant interaction. Soluble solids were adequate up to pruning levels of 6 buds per square meters but fell below 23° Brix at higher bud numbers.

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