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For 4 years, six-flowered clusters on 20, unthinned, open-pollinated `Empire'/MM106 trees were labeled at bloom and fruit drop monitored at the king (K) and lateral positions L1 (basal) to L5 (distal) (100 to 120 clusters/year). Depending on year, fruit dropped in 1, 2, or 3 major periods by 8 weeks postbloom (PB), with total percent dropped between 65% and 75%. K fruit dropped least, L4 and L5 most. Trends were that K fruit at October harvest were largest and heaviest (significantly so in some years) and L5 fruit smallest. In nine trees, hand-thinned to single-fruited spurs at 12 days PB, where the fruit at the retained position was known, there was no statistical difference in fruit weight, fruit size, or seed count between cluster positions at final harvest, although L5 fruit tended to be smallest. Numbers of spurs labeled varied from 45 to 72. Percent fruit retained at each position at October harvest was K = 89%, L1 or L2 = 87%, L3 = 83%, L4 = 83%, and L5 = 85%. Presumably, in unthinned trees the limited resources are preferentially taken by the K fruit, which especially seems to reduce set and size of its nearest lateral fruit. However, in thinned trees under lighter cropping stresses, a fruit retained at any of the positions within a cluster has a similar potential for achieving the size and weight typically seen in king fruit.
Choice of cultivar, training system, planting density, and rootstock affect orchard performance and profitability. To provide guidance to growers in northern cold climates on these choices, a field trial was established in Peru, Clinton County, NY, in 2002, with two apple cultivars (Honeycrisp and McIntosh). From 2002 through 2016, we compared Central Leader on ‘M.M.111’; Slender Pyramid on ‘M.26’ and ‘Geneva® 30’ (‘G.30’); Vertical Axis on ‘M.9 (Nic® 29)’ (‘M.9’), ‘Budagovsky 9’ (‘B.9’), and ‘G.16’; SolAxe on ‘M.9’, ‘B.9’, and ‘G.16’; and Tall Spindle on ‘M.9’, ‘B.9’, and ‘G.16’. Central Leader was planted at 539 trees/ha, Slender Pyramid at 1097 trees/ha, Vertical Axis and SolAxe at 1794 trees/ha, and Tall Spindle at 3230 trees/ha. Cumulative yield was higher with ‘McIntosh’ than with ‘Honeycrisp’. High planting densities (Tall Spindle) gave the highest cumulative yields (593 t·ha−1 on ‘McIntosh’ and 341 t·ha−1 on ‘Honeycrisp’). Tall Spindle (3230 trees/ha) on ‘M.9’ appeared to be the best option for ‘McIntosh’. On the other hand, for a weak-growing cultivar such as ‘Honeycrisp’, Tall Spindle on ‘B.9’ (366 t·ha−1) and Slender Pyramid (1097 trees/ha) on ‘G.30’ (354 t·ha−1) were the two combinations with the highest cumulative yield, largest fruit size (220–235 g), and greatest efficiency index (4.6–3.9 kg·cm−2).
Orchard profitability relies on multiple factors such as cultivar, planting density, training system, rootstock, and fruit quality but is also strongly affected by growing climate and soil resources. To evaluate orchard profitability in a northern cold climate, a field trial was planted in Peru, Clinton County, NY, in 2002, with two apple cultivars (Honeycrisp and McIntosh), where we compared the Central Leader (CL) training system on ‘M.M.111’ rootstock; Slender Pyramid (SP) on ‘M.26’ and ‘Geneva® 30’ (‘G.30’); Vertical Axis (VA) on ‘M.9 (Nic® 29)’ (‘M.9’), ‘Budagovsky 9’ (‘B.9’), and ‘G.16’; SolAxe (SA) on ‘M.9’, ‘B.9’, and ‘G.16’; and Tall Spindle (TS) on ‘M.9’, ‘B.9’, and ‘G.16’. CL was planted at 539 trees/ha, SP at 1097 trees/ha, VA and SA at 1794 trees/ha, and TS at 3230 trees/ha. The aim of this study was to evaluate the economic profitability of ‘Honeycrisp’ and ‘McIntosh’ at a wide range of planting densities, training systems, and rootstocks for cold areas such as northern New York state. A secondary goal was to assess the effect of various economic factors on the net present value (NPV) of each combination of training system, rootstock, and density. High NPV was achieved with ‘Honeycrisp’ (≈$450,000/ha), whereas NPV was significantly lower with ‘McIntosh’ (≈$80,000/ha). Within ≈5 years, ‘Honeycrisp’ planted in a TS (3230 trees/ha) reached a positive NPV, whereas 9 years were needed when ‘Honeycrisp’ was planted in a CL system at 539 trees/ha. With ‘McIntosh’, break-even year to positive NPV (BYPNPV) was reached at 9 years for TS on ‘M.9’. Most of the other training system and rootstock combinations needed up to 11–13 years to show a positive NPV. The most important variables affecting orchard NPV in our trial were fruit price and yield. The best option for ‘Honeycrisp’ in northern New York State appears to be TS on either ‘B.9’ or ‘M.9’, whereas with ‘McIntosh’, the best option appears to be TS on ‘M.9’.
The Geneva® Apple Rootstock Breeding program initiated in 1968 by Cummins and Aldwinckle of Cornell University and continued as a joint breeding program with the USDA-ARS since 1998, has released a new dwarf apple rootstock named Geneva® 41 or G.41. G.41 (a progeny from a 1975 cross of `Malling 27' × `Robusta 5') is a selection that has been tested at the N.Y. State Agricultural Experiment Station, in commercial orchards in the United States, and at research stations across the United States, Canada, and France. G.41 is a fully dwarfing rootstock with vigor similar to M.9 T337, but with less vigor than M.9 Pajam2. It is highly resistant to fire blight and Phytophthora with no tree death from these diseases in field trials or inoculated experiments. G.41 has also shown tolerance to replant disease. Its precocity and productivity have been exceptional, equaling M.9 in all trials and surpassing M.9 in some trials. It also confers excellent fruit size and induces wide crotch angles in the scion. It appears to be very winter hardy and showed no damage following the test winter of 1994 in New York. Propagation by layering in the stool bed G.41 is not consistent and may require higher layering planting densities or tissue culture mother plants to improve its rooting. G.41 also produces some side shoots in the stool bed. The nursery liners of G.41 produce a smaller tree than G.16 liners, but similar to M.9, which is very acceptable. Unlike G.16, G.41 is not sensitive to latent viruses. G.41 has similar graft union strength to M.9 and requires a trellis or individual tree stake when planted in the orchard. Suggested orchards planting densities with this rootstock are 2,000-4,000 trees/ha. This rootstock has been released for propagation and commercial sale by licensed nurseries.
The Geneva® Apple Rootstock Breeding program, which was initiated in 1968 by Dr. James Cummins and Dr. Herb Aldwinckle of Cornell University and which has been continued as a joint breeding program with the U.S. Dept. of Agriculture Agricultural Research Service (USDA-ARS) since 1998, has released a new semi-dwarfing apple rootstock which is named Geneva® 935 or G.935. G.935 (a progeny from a 1976 cross of `Ottawa 3' × `Robusta 5') is a selection that has been widely tested at the New York State Agricultural Experiment Station in Geneva, N.Y., in commercial orchards in the United States and at research stations across the United States and Canada. G.935 is a semi-dwarfing rootstock that produces a tree slightly larger than M.26. G.935 is the most precocious and productive semi-dwarf rootstock we have released. It has had similar yield efficiency to M.9 along with excellent fruit size and wide crotch angles. It showed no symptoms of winter damage during the 1994 test winter in N.Y. G.935 is resistant to fire blight and Phytophthora; however. it is susceptible to infestations by woolly apple aphids. G.935 has shown tolerance to replant disease complex in several trials. It has good propagation characteristics in the stool bed and produces a large tree in the nursery. G.935 has better graft union strength than M.9, but will require a trellis or individual tree stake in the orchard to support the large crops when the tree is young. G.935 will be a possible replacement for M.26. Suggested orchards planting densities with this rootstock are 1,500-2,500 trees/ha. It has been released for propagation and sale by licensed nurseries. Liners will be available in the near future.
Several field experiments to assess the effect of tree size and crop load on fruit size and yield efficiency were conducted in cling peach and nectarine orchards of different harvest seasons in Chile. Trees were randomly selected in each orchard and then hand-thinned at the beginning of pit hardening to a wide range of crop loads. The fraction of above-canopy photosynthetically active radiation (PAR) intercepted by the canopy (PAR i) was determined at harvest. All fruits were counted and weighed and average fruit weight calculated. Crop load and yield were normalized by tree size measured by intercepted PAR i. For each orchard, the relationship between crop load and fruit size or crop load and yield efficiency was assessed by regression analysis. Fruit size distribution was calculated from fruit size adjusted for fruit load assuming a normal fruit size distribution and valued according to shipment date and price obtained from a Chilean export company. Using crop load as a covariate, fruit size adjusted for crop load was compared for nectarine and peach cultivars. Fruit size adjusted for fruit load and yield efficiency was greater with late season cultivars than the early or midseason cultivars. Predicted crop value (PCV), normalized in terms of PAR intercepted, was calculated for all the cultivars. Large differences in predicted crop value were found for early, midseason, and late ripening nectarines. Early and late ripening cultivars had the highest predicted crop value, especially at lower crop loads and larger fruit sizes. The early season cultivars had high crop value as a result of higher fruit prices, whereas the late season cultivar had high crop value as a result of higher production. With cling peaches, the early season cultivar ‘Jungerman’ had a lower predicted crop value than the late season cultivars ‘Ross’ and ‘Davis’. For cling peaches, the highest PCV was achieved at a relatively high crop load with high yield and small fruit size.
Abstract
A tree design, called the “palmette leader”, for improving the distribution of light within the tree canopy is described. The tree is a modification of the common central leader, and is formed by having a complete lower whorl of scaffold branches with a flat north-south-oriented palmette leader above. The large permanent gaps in the upper canopy ensure good light distribution, which was confirmed with canopy transects using fisheye photography. Preliminary evaluations of tree performance with ‘McIntosh’ apples (Malus domestica Borkh.) indicated that cumulative yields, fruit soluble solids content, and fruit dry matter were greater than well-trained central leaders, but fruit size and fruit color were similar. The improved light penetration into the center of the palmette leader compared to the central leader was found to induce higher photosynthesis of interior spur leaves exposed by summer pruning in August. Management of the palmette leader trees was found to be relatively simple.
We are evaluating the severity of apple replant disease (ARD)-characterized by stunted tree growth in replanted orchards, attributed to root pathogens and/or edaphic conditions-and testing preplant soil treatments for control of this wide-spread problem. Soil samples were collected during 1996–98 at 17 orchards in New York's major fruit growing regions and plant-parasitic nematodes and nutrient availability were quantified. Apple seedlings and potted trees on M.9 rootstocks were grown in fumigated and non-fumigated soil samples as a diagnostic bioassay for ARD severity. Factorial combinations of metam sodium, consecutive cover crops of Brassica juncea `Forge' and Sorghum sudanense `Trudan 8', and fertilizer/lime amendments were applied as preplant treatments at each orchard, 9 to 12 months before trees were replanted. Diagnostic bioassays indicated severe ARD at more than half the sites, and nematodes were not a major factor. Responses to preplant soil treatments were highly variable across the 17 farms. The best tree growth and yields followed preplant metam sodium at some sites, Brassica juncea and Sorghum sudanense at others, or fertilizer amendments at a few others. Tree responses to combined preplant soil treatments were often additive, and greater at irrigated sites. Comparisons of preplant diagnostic bioassay results with subsequent tree responses to metam sodium at the 17 orchards indicated that diagnostic tests predicted from 7% to 75% of tree growth response to soil fumigation, varying substantially across years and sites. It appeared that ARD was variable and site specific in New York orchards, and could not be controlled effectively with a uniform preplant soil treatment across our major fruit-growing regions.
ReTain™, a commercial plant growth regulator containing aminoethoxyvinylglycine, an inhibitor of ethylene production, was applied 4 weeks before normal harvest to `Jonagold' trees and the effects on fruit maturity and quality at harvest, and quality after air and controlled atmosphere storage was investigated. When fruit were harvested from 3 to 6 weeks after treatment, fruit ripening was inhibited as indicated by lower internal ethylene concentrations, delayed starch hydrolysis, and lower levels of skin greasiness. A number of factors indicated that other aspects of fruit metabolism were affected by the compound. Treated fruit were softer than nontreated fruit at the first harvest, and the benefits of ReTain on firmness appeared only at the later harvests. Also, at each harvest date, average fruit weight of ReTain-treated fruit was lower than nontreated fruit. We have investigated the possibility the ReTain and/or the accompanying surfactant, Silwet, inhibited leaf photosynthesis, thereby leading to altered carbon metabolism. Trees were unsprayed, or sprayed with surfactant, and ReTain plus surfactant. No treatment effects on photosynthesis were detected. However, leaf photosynthesis rates were generally low and quite variable. Measurements of fruit diameter confirmed that the increase in fruit volume following treatment was ≈2% less on the ReTain plus surfactant-treated fruit than nontreated fruit. The increase in fruit volume for the Silwet treatment was ≈1.5% less than in untreated fruit. The data indicates a rapid change in fruit volume as fruit changed in color. Inhibition of ethylene by ReTain may be an important factor influencing fruit size.