In 1981, four apple cultivars were established as a low trellis hedgerow on M.9 or free-standing central leaders on M.7 at the recommended or half the recommended spacing with the close planted trees either root pruned annually at bloom or hedged in August. Planting at half the spacing and annual summer hedging 2 sides decreased TCA 25% and canopy volume 51% with no effect on shoot growth, while annual root pruning decreased TCA 34%, canopy volume 50% and shoot length 25%. Planting at half spacing and either hedging or root pruning reduced yields per tree. Efficiency as measured by yield TCA was decreased by hedging and as measured by yield/m3 canopy volume was increased by both treatments with hedging having the greatest effect. The cumulative yield/ha was increased by both hedging and root pruning with no difference between them. Fruit size was decreased by close planting and root pruning caused a greater decrease than hedging. Close planting increased the number of spurs and shoots and LAI per unit volume of canopy with no difference between hedging or root pruning. `Empire' outproduced `Smoothee' and `Delicious' on the trellis and `Lawspur' had higher yields than any other cultivar in the central leader.
David C. Ferree
In 1987, `Smoothee Golden Delicious' (`Smoothee') and `Lawspur Rome Beauty' (`Lawspur') apple (Malus domestica Borkh,) trees were planted and trained as central leaders or palmette leaders on M.7 and Mark rootstocks or were planted as slender spindles on Mark rootstocks. `Smoothee' trees were larger and had consistently greater yields and production per unit trunk cross-sectional area (TCA) than `Lawspur' trees. Slender spindle trees had lower early yields per tree and TCA but had greater cumulative yields per hectare than trees in the other training systems. In the fifth and sixth growing seasons, `Smoothee' trained as palmette leaders tended to have higher yields per hectare then central leader trees. Training system had little influence on `Lawspur' tree yields. Limb bending in 1989 increased flower density in 1989 and 1990. Cumulative yield per hectare increased 11% as a result of limb bending of trees on Mark rootstock, but bending had no influence on trees on M.7 rootstock. `Smoothee' on Mark had higher cumulative yields per hectare with the palmette leader and central leader than either `Smoothee' on M.7 in either training system or any combination with `Lawspur'.
David C. Ferree
`Melrose'/M.26 apple (Malus domestics Borkh.) trees were mechanically root-pruned annually for 9 years at bloom to a 25-cm depth at 80 cm from the trunk on two sides. An evaluation of the number of roots of four size categories on the exposed wall of a 1.2 x 2-m trench located 1 m from the trunk indicated that root pruning caused a reduction in all root size categories. Roots < 1 mm in diameter were reduced 20% by root pruning, while the reduction in larger roots was nearly double this amount. The effect of root pruning on root distribution was greatest in the top 30 cm of soil, parallel to the location of the root-pruning cut. Roots below 30 cm were unaffected. The number of roots in all size categories in samples taken parallel and perpendicular to the row decreased linearly with soil depth.
David C. Ferree
In 1987, `Starkspur Supreme Delicious' and `Melrose' were planted on eight apomitic apple selections made in Germany by Dr. Hanna Schmidt for use as rootstocks and compared to trees on M.7. Selection 2, was the most precocious, followed by trees on M.7, with selections 1 and 7 being less precocious than M.7. Selections 2 and 8 were 25% larger than M.7, while 1, 3, 4, and 7 were similar in size and 5 was 15% smaller than trees on M.7. Selections 2 and 8 had the highest cumulative yields/tree, followed by trees on M.7, with all other selections having lower yields. Internal bark necrosis (IBN) developed on the `Delicious' trees, with the most-severe symptoms on selections 1, 3, 4, 5, 6, and 7, with less-severe symptoms on 8 and very little present on trees on M.7. IBN was correlated with leaf Mn levels. In 1995, the highest density of flowering spurs occurred on M.7 and selections 3 and 7, with lower densities in selections 2 and 5. Selection 2 had the highest density of non-fl owering spurs, followed by selection 5, with all others having lower densities similar to trees on M.7.
David C. Ferree
The apple (Malus ×domestica Borkh.) cultivars Starkspur Supreme Delicious and Melrose were planted in 1987 on eight apomictic apple rootstock selections made in Germany by Dr. Hanna Schmidt and on M.7. Selections 2 [M. hupehensis (Pamp.) Rehd. parentage] and 8 [M. sieboldii (Regel) Rehd. parentage] were similar to M.7 in precocity, cumulative yield per tree, and yield efficiency, while the other selections with M. sargenti Rehd. in their parentage were slower to flower and had lower yields and yield efficiencies. Selections 2 and 8 tended to result in larger trees than M.7, while the selections with M. sargenti parentage were generally similar to M.7 in size. Except for trees on M.7 and selection 2, `Starkspur Supreme Delicious' developed more severe symptoms of internal bark necrosis (IBN) than did `Melrose', which normally does not show IBN. However, `Melrose' showed IBN symptoms on selections with M. sargenti parentage. IBN symptoms were positively correlated with leaf Mn concentrations. Influence of rootstocks on other nutrient elements, although significant, were small compared to the effect on Mn. A significant interaction occurred between cultivar and rootstock in their effects upon branch morphology, mostly because fewer flowering spurs and more vegetative spurs were observed on `Melrose' than on `Starkspur Supreme Delicious' when grafted on Selection 2. These apomictic selections offered no advantage over M.7 as rootstocks for apples.
David C. Ferree
Container-grown apple trees on a range of rootstocks were exposed to different levels of soil compaction created by changing soil bulk density. In 1998, with soil bulk densities of 1.0, 1.2, and 1.4, there was no interaction of rootstock and soil compaction for shoot growth of `Melrose' trees on 7 rootstocks. However, in 1999, with soil bulk densities of 1.0 and 1.5, a significant interaction on shoot growth did occur with six rootstocks. Shoot length of trees on M.9, M.7, and G.30 were less influenced than G.16, M.26 and MM.106. A bulk density of 1. 5 caused a decrease in dry weight of shoots, leaves, and roots of trees on all rootstocks. Compacted soil resulted in a decrease in leaf concentration of K and B and an increase in Mg and Mn.
David C. Ferree
`Jonathan'/M.26 apple (Malus domestics Borkh.) trees were root-pruned annually on two sides, 60 cm from the trunk, to a depth of 40 cm for 6 years while dormant, at bloom, or in mid-June. Root pruning reduced terminal shoot growth by ≈30% in 1985-89 with no influence in 1990. Cumulative yield was reduced by root pruning at bloom (14%) or mid-June (20%), and cumulative yield efficiency [kg·cm-2 trunk cross-sectional area) was reduced by root pruning with no difference among pruning times except in 1 year, where abundant moisture throughout the season appeared to negate the effect. The intensity of biennial bearing was reduced by root pruning with no relationships to time of pruning. Root pruning resulted in a decrease in large fruit and an increase in small fruit in 3 of the 6 years. A covariant analysis with yield showed that root pruning reduced average fruit size. Root-pruned trees produced firmer fruit with an increased soluble solids concentration and had less preharvest drop than nonpruned trees. Under severe drought conditions in 1988, root pruning reduced net photosynthesis and transpiration; supplemental water (57 liters·week-1) increased transpiration and fruit size at harvest.
Peter M. Hirst and David C. Ferree
One way in which rootstocks may influence production efficiency is by altering the number of spurs, and in particular reproductive spurs. However, rootstock influences on the morpholgy of shoots have not been quantified. Measurements were made on `Starkspur Supreme Delicious' trees growing on 17 rootstocks and planted in 1984 as part of the NC-140 regional rootstock trial. In each of the 6 years from 1988-1993, the length of the 2-year old section of wood of selected branches was measured and the number of spurs, flowers and shoots counted. For all rootstocks, trunk cross-sectional area was closely related to shoot length. Trees on P.22 (the most dwarfing rootstock in the planting) had shoot lengths 40-50% of those of trees on seedling rootstocks. For each rootstock, there was a strong negative relationship between shoot length and spur density, but there was not a common relationship among rootstocks. Similarly, flower number per shoot was also related to shoot length with different relationships for each rootstock. Flower density was not related to vigor for any of the rootstocks.
Steven J. McArtney and David C. Ferree
Early season vegetative development of grapevines was studied in the year after imposing three cropping levels to mature `Seyval' vines in the field or establishing two light levels to potted `DeChaunac' vines growing in the greenhouse. Heavily cropped `Seyval' vines (averaging 90 buds, 15.8 kg fruit per vine over the previous two growing seasons) had 85% fewer count buds and 31% fewer non-count (latent) buds than lightly cropped vines (averaging 25 buds, 9.7 kg fruit per vine). The rate of leaf area expansion was reduced on heavily cropped vines. Covering `DeChaunac' vines in the greenhouse with 80% shade from bloom onwards reduced the leaf area per shoot in the year after treatment by reducing both the rate of leaf appearance and the rate of leaf expansion. The leaf at node four from the base of the shoot had the greatest area on both shaded and control vines; however, the area was reduced 33% on shaded vines. Data from the greenhouse experiment were used to model the effect of leaf size at the transition from sink to source on total source leaf area per shoot. Prior to bloom the total source leaf area per shoot was increased when individual leaves became sources earlier, i.e., at a lower percent of their final size. Whether a leaf became a source at either 30%, 50%, or 80% of its final size had little effect on total source leaf area per shoot after bloom. The proportion of source to sink leaf area at bloom was greater than 90% for both slow- and rapidly growing shoots (those on shaded and control vines, respectively). Expansion of grapevine leaves was reduced by heavy cropping and low light levels in the previous year, greatly reducing the source leaf area per shoot.
Ann K. Hummell and David C. Ferree
A 2-year field study was initiated in 1994 to examine the interactions between crop load and cluster exposure and their influences on the yield and fruit quality of mature, own-rooted `Seyval blanc' grapevines. Light, moderate, and heavy crop loads were established near bloom by cluster-thinning vines planted at 2.6 × 3.0-m spacing to around 20, 40, and 80 clusters per vine, respectively. At veraison, three clusters per vine were given one of three natural shaded treatments: fully exposed, partially shaded, and densely shaded. Vines with the heavy crop load produced higher yields per vine and lower cluster and berry weights. Heavy vine clusters tended to be more green in 1994 and possessed lower pH and soluble solid concentrations in both years compared to other crop loads. Compared to densely shaded clusters, fully exposed clusters had smaller average cluster and berry weights, lower titratable acidity, higher pH and soluble solid concentrations, and more yellow coloration. In 1994, no significant interactions were found for any fruit quality or yield characteristics. In 1995, significant interactions were found for soluble solids and hue angle, but not for yield, pH, or titratable acidity. These results suggest that the crop load of the vine and microclimate around the cluster, in addition to their individual effects, sometimes interact to affect fruit quality in `Seyval blanc' wine grapes.