Spring frosts can be a limiting factor for sweet cherry production and very little is known about frost susceptibility of new sweet cherry cultivars. This study reports on floral bud injury of a number of recently introduced sweet cherry cultivars after 10 spring frosts in Apr. 2008. Floral buds at the first white stage were collected from late-ripening sweet cherry cultivars that were part of a randomized and replicated evaluation block. Blossoms were selected from various positions within a tree in a 1-m band centered around 1.5 m above the ground. The blossoms were brought into the laboratory, cut open, and placed into two groups: live (green) or dead (brown or browning) pistil. ‘Staccato’ and ‘Sentennial’ were the least affected followed by ‘Lapins’ and ‘Sweetheart’. ‘Sovereign’ was most susceptible to the subfreezing temperatures in the spring of 2008. There was a reasonably good relationship between the percentage of live buds per tree in the spring and yield at harvest later in the summer.
Yield components of 8- to 10-year-old trees were compared among `Kieffer' [Pyrus communis (L.) x Pyrus pyrifolia (Burro.)] and `Harrow Delight' and `Harvest Queen' [Pyrus communis (L.)]. `Kieffer' set more fruit than the other cultivars, even though flower density was similar. `Kieffer' also had similar size or larger fruit than `Harrow Delight' or `Harvest Queen'. Path analysis showed that the direct and indirect effect of fruit number on yield was important for all cultivars. Flower density only had a small direct effect on yield and this was at times negative. Fruit size had a small effect on yield when compared to fruit number.
The effect of fruit on shoot growth, leaf area, and on dry weight (DW) partitioning into leaves, fruit, trunk, and branch sections was investigated using 7-year-old `Lambert' sweet cherry (Prunus avium L.) trees. Dormant trees were sampled in the spring, and fruiting and deblossomed trees were sampled and compared at fruit harvest and just before leaf fall. Fruiting reduced shoot growth, leaf area, and above-ground DW accumulation of the trees. The annual above-ground DW accumulated was 13.4 kg for fruiting trees and 16.0 kg for nonfruiting trees. The greatest proportion of above-ground DW was partitioned to wood, whereas the least was partitioned to fruit. Current-season's growth (wood and leaves) appears to be a greater sink for photosynthates than is fruit because a greater proportion of above-ground DW was partitioned to current-season's growth than to fruit.
Frank Kappel and Jean Lichou
The effect of rootstock on the flowering and fruiting response of sweet cherries (Prunus avium L.) was investigated using 4-year-old branch units. The cherry rootstock Edabriz (Prunus cerasus L.) affected the flowering and fruiting response of `Burlat' sweet cherry compared to Maxma 14 and F12/1. Branches of trees on Edabriz had more flowers, more flowers per spur, more spurs, more fruit, higher yields, smaller fruit, and a reduced fruit set compared to the standard rootstock, F12/1. One-year-old branch sections had more flowers and fruit, higher fruit weight, and heavier fruit size compared to older branch portions.
Frank Kappel and Rob Brownlee
To determine how different training systems affected early growth and fruiting (first 5 years), `Conference' pear (Pyrus communis L.) trees on Quince A (Cydonia oblonga L.) rootstock were trained to angled trellis, slender spindle, vertical axe, or Y-trellis. The trees of the Y-trellis had the greatest spread after 5 years, and the vertical axe and slender spindle trees were the tallest. The Y-trellis trees had the highest light interception and had significantly higher yields in 1997 than the other training systems. Average fruit weight was inversely related to crop load.
Gerry Neilsen and Frank Kappel
Leaf nutrient concentration of `Bing' sweet cherry (Prunus avium L.) was affected by rootstock over 4 years in the Pacific Northwest. Trees on GM 79, GI 148/1, GI 195/1, and GI 196/4, which had higher yields than Mazzard, also had lower leaf K and, excepting GM 79, lower leaf Mg concentration. Use of GI 195/1 and 196/4 resulted in lower leaf N than use of Mazzard. These higher-yielding rootstocks will require greater attention to these macronutrients, especially on infertile soil sites. Micronutrient nutrition was little affected by rootstocks, which tended to have the low leaf Zn concentrations typical of irrigated Pacific Northwest orchards. GM 9 and GM 61/1 rootstocks were more dwarfing than Mazzard, with GM 9 leaves having lower K, but higher P, Mg, and Mn concentrations. GM 61/1 had lower leaf concentrations of most nutrients relative to Mazzard.
Cheol Choi and Frank Kappel
Inbreeding and coancestry coefficients were calculated for 66 sweet cherry (Prunus avium L.) selections released from four breeding programs in North America (HRIO, Vineland, Ont., IAREC, Prosser, Wash., NYSAES, Geneva, N.Y., and PARC, Summerland, B.C.). Highly used founding clones were `Black Heart', `Emperor Francis', `Empress Eugenie', `Napoleon' and `Windsor'. Coefficients of coancestry between all selections and these clones averaged 0.038, 0.045, 0.060, 0.091, and 0.033, respectively. In these five founding clones, coefficients of coancestry in self-compatible selections were over twice as much as those in self-incompatible selections except `Windsor'. In the analysis of coefficients of coancestry between self-incompatible and self-compatible sweet cherry, almost 20% of self-incompatible selections represent more than a half-sib relationship (0.125) to self-compatibles. Increasing and maintaining genetic diversity is needed in sweet cherry breeding program in North America for continued breeding progress.
Frank Kappel, M. Bouthillier, and L. Veto
Buds from 12-year-old `Bing' sweet cherry trees were collected biweekly from May 25, 1989 to August 31, 1989 and periodically therafter until the spring of 1990. Buds were partially dissected by removing outer bud scales, then fixed in a solution of 3% glutaraldehyde and 2% formaldehyde for 24 hrs. The buds were then stored in phosphate buffer solution at 6.8 pH at 4C for a maximum of 6 months. Buds examined with the SEM were critical point dried, mounted and coated with gold. Anthesis occurred April 28 and fruit were harvested July 6. Rapid changes in the development of the buds occurred during the period between July 7 and July 20. Flower primordia were just barely visible on July 7 in the most advanced buds but by July 20 multiple flowers were visible with sepal primordia apparent. By Aug 3 petals were clearly defined and stamen primordia evident. By August 17 anthers were clearly visible and pistil primordia were evident. Most buds produced 2 flowers with some producing a third. The third flower trailed the other two buds in development.
Frank Kappel, Bob Fisher-Fleming, and Eugene Hogue
The relationship between the objective assessment of analytical measures of sweet cherry (Prunus avium L.) fruit quality and the corresponding sensory panel rating was studied. The optimum size, based on average fruit weight, for sweet cherries was 11 to 12 g. A nine-row or 29- to 30-mm-diameter sweet cherry would be the equivalent industry standard. When two separate panels were conducted with overlapping samples, panelists had similar results for optimum fruit size. The optimum color is represented by the #6 color chip of the prototype of the Centre Technique Interprofessionnel des Fruits et Légumes (CTIFL) scale (#5 in new commercial CTIFL chart). A fruit firmness between 70 and 75 using a Shore Instrument durometer was considered optimum. Minimum soluble solids concentration (SSC) for sweet cherries was between 17% and 19% and optimum pH of the juice was 3.8. The optimum sweet–sour balance was between 1.5 and 2 (SSC/ml NaOH).
Frank Kappel, Michel Bouthillier, and Rob Brownlee
`Sweetheart' sweet cherry trees (Prunus avium L.) were summer-pruned for four summers (1991-94) either before or after harvest and at two levels, removing 1/3 or 2/3 of current-season growth by heading cuts. In an additional postharvest treatment, some current-season growth was removed by thinning cuts. The preharvest 1/3 treatment had the highest cumulative yield during the experiment. Higher yields were obtained following preharvest than postharvest treatments, and following less severe treatments (removing 1/3 of current-season growth) than more severe (removing 2/3) treatments. These increased yields were for the early stages of orchard production. Average fruit mass was not affected by any of the treatments. The summer-pruned trees had smaller trunk cross-sectional area (TCSA) increments over the trial and their final TCSA was smaller than that of the control trees.