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Endothall [7, oxybicyclo (2,2,2) heptane-2-3 dicarboxylic acid] is an aquatic herbicide which has potential for use as a blossom thinning agent for apples. Trials conducted in Washington State, New Zealand and Australia on several apple cultivars indicate Endothall is a safe, consistent blossom thinner. Cultivars treated were `Golden Delicious', `Delicious', and `Gala'. Single and repeat applications were used in the New Zealand tests. With multiple applications of Endothall, no fruit marking occurred on any of the test cultivars. In temperate fruit zones with extended apple bloom periods, multiple applications of a low rate of Endothall may he beneficial for reducing fruit set and biennial hearing.
‘Royal Gala’ apple scions (Malus ×domestica) were grafted onto 1-year-old rootstock stools of ‘M.9’ (M.9), ‘M.M.106’ (MM.106), ‘Merton 793’ (M.793), and ‘Royal Gala’ [R.G (control)] to elucidate how the dwarfing apple rootstock (M.9) modified scion architecture, the time from grafting when this started, and whether changes in scion architecture were explained by some endogenous hormones present within the scion. At the end of the first season of growth (April), the final length and node number of the primary shoot were similar for scions on M.9 and R.G. However, M.9 appeared to limit the number of secondary shoots formed on the primary shoot during summer. In addition, the proportion of secondary shoots that were actively extending in fall was lower for M.9; consequently, the final mean length of the secondary shoots was slightly shorter for M.9 compared with R.G. Collectively, these subtle effects of M.9 significantly reduced the final total shoot length of the scion compared with R.G. The final dry weight of the scion and root system was also lower for M.9 than MM.106, M.793, and R.G. The mean rate of indole-3-acetic acid diffusing from the apex of the primary shoot progressively declined from February onward irrespective of rootstock, whereas the mean concentration of zeatin riboside (ZR) in the xylem sap increased during the same period, and these events appeared to coincide with cumulative increases in the number of axillary growing points formed on the scion. Despite this general trend, M.9 had a greater concentration of ZR in the xylem sap during February compared with R.G, but the primary shoot on M.9 did not develop more axillary growing points, indicating that other endogenous hormonal signals were also involved in regulating scion branching. By March, M.9 lowered gibberellin A19 (GA19) concentration in the xylem sap of the scion significantly compared with R.G. We conclude that dwarfing apple rootstocks may limit root-produced GA19 supplied to shoot apices of the scion, where GA19 may be a precursor of bioactive gibberellin A1 required for shoot extension growth.
Abstract
Fruiting laterals were tagged within the inner and outer canopy zones of the basal, mid, and upper tiers of dormant, mature central-leader ‘Granny Smith’ apple (Malus domestica Borkh.) trees and were classified into pendant (>120°), horizontal (30°-120°), and vertical (0°-30°) types. Transmission of photosynthetic photon flux (PPF) to spur sites on tagged laterals was measured in mid-season and fruits from these sites were harvested at commercial maturity for assessment of fresh weight, soluble solids concentration (SSC), starch pattern index, and background color. Pendant laterals produced fewer, smaller, and greener fruit per flowering spur than horizontal or vertical laterals. Fruit fresh weight and soluble solids concentration increased with increasing height in the canopy and were higher in the outer compared with the inner horizontal canopy position. Background color followed a trend opposite to that of fresh weight and soluble solids concentration, with fruit from the lower inner canopy regions being greenest. Both fresh weight and SSC showed highly positive correlations with the percentage transmission of PPF. Fruit set showed a positive correlation with PPF, although the relationship was weaker than that for fresh weight or SSC. PPF penetration was lower to pendant laterals than to horizontal and vertical laterals and declined from upper to lower and from outer to inner canopy positions. Pendant fruiting laterals received < 15% of PPF, irrespective of location within the canopy.
Endothall [7, oxabicyclo (2,2,1) heptane-2-3 dicarboxylic acid] is an aquatic herbicide with potential use as a blossom thinner for apples (Malus domestics Borkh.). Trials conducted in Washington, New Zealand, and Australia on several apple cultivars indicate that endothall is a safe, consistent blossom thinner. Cultivars treated were `Golden Delicious', `Delicious', `Royal Gala', and `Granny Smith'. Single and repeat applications were used in the New Zealand and Washington tests. With multiple applications of endothall, no fruit marking occurred on any of the test cultivars. In temperate fruit zones with extended apple bloom periods, multiple applications of endothall at a low rate may be beneficial for reducing fruit set and biennial bearing.
Foliar applications of monocarbamide dihydrogensulfate (D-88, Unocal Chemicals Division) at rates of 0, 2.5 ml/1, 3.75 ml/1 or 5.0 ml/1 were made to mature apple trees of “Fuji”, “Royal Gala” or “Braeburn” on MM106 root-stock. Treatments were applied dilute when spurs were at 95% full bloom. D-88 was applied at 5.0 ml/1 to “Fuji” at three different times during the day (0730, 1400 or 1810) with and without surfactant in an attempt to evaluate the effect of different atmospheric and drying conditions. Fruit set (number of fruit per 100 flower clusters) was determined after natural fruit drop.
D-88 had no effect on fruit set of “Royal Gala” or “Braeburn”. There was a linear effect between D-88 rate and fruit set on “Fuji”, with the 5.0 ml/1 rate reducing set by 30%. D-88 affected the number of fruit at individual fruiting sites, most significantly the percentage of flower clusters setting 3 fruits decreasing with increasing rate. Timing and surfactant had no effect.
Fruit finish, mean fruit weight, seed number and soluble solids concentration were measured at harvest.
Partial thinning of peach (Prunus persica L. Batsch) during bloom to 50% of the necessary level by hand, and followed by adjustment hand thinning at 42 days after full bloom (DAFB) was compared to a similar degree of thinning accomplished entirely at 42 DAFB by hand. Partial flower thinning altered the distribution of fruit by diameter, increasing the percentage of large diameter (≥62.0 mm) fruit harvested compared to unthinned trees or trees thinned entirely at 42 DAFB. Although shoot number per limb was not altered by thinning time, the distribution of shoots by length was affected, increasing the percentage of long shoots (≥20.0 cm). Compared to unthinned trees and trees thinned at 42 DAFB, partial flower thinning increased the subsequent development of flower buds per shoot and the number of flower buds per node. Number of flower buds on the proximal five nodes of shoots 15.0-30.0 cm in length was increased, although not on shoots 5.0-7.0 cm in length. Additional trials established that airblast spray application of AMADS was effective in achieving a similar level of thinning as that accomplished by partial flower thinning by hand in previous experiments. The degree of flower removal exhibited a linear response to chemical concentration. Fruit diameter on chemically flower-thinned trees was greater at adjustment thinning time, when compared to trees thinned by hand at 42 DAFB only. Distribution of fruit at harvest indicated a larger percentage of fruit >65.0 mm in trees which received partial flower thinning in comparison to trees thinned at 42 DAFB only. As a result, overall crop value was increased, based on the commercial processing peach price structure at the time of harvest. Chemical name used: 1-aminomethanamide dihydrogen tetraoxosulfate (AMADS)
Export-packed fruit of `Braeburn' apple ware collected on three dates corresponding to the early, mid and late periods of commercial harvest. Fruit were segregated into categories determined by background color, combined with percent fruit surface area with red blush of <40%, 40-70% and >70%. A separate category comprised fruit which showed marginal sunburn discolouration. Fruit were assessed at harvest and after 16 weeks air storage at O°C. Quality and maturity indices which were affected by harvest date included starch pattern index, flesh firmness and soluble solids concentration (SSC). However differences due to harvest data were not evident after storage. Fruit with more yellow background color or marginal sunburn were distinguished by advanced starch hydrolysis, higher internal ethylene concentration and higher SSC at harvest. After storage these fruit had yellowest background color, softer flesh and highest SSC. Fruit with green-yellow background color and >70% blush showed similar but less pronounced trends. Organoleptic assessment after storage showed a higher frequency of inferior texture and juiciness associated with categories of fruit with indices indicating advanced maturity at harvest and following storage.
To investigate a flesh browning (FB) disorder in Pink Lady apple [Malus ×sylvestris (L.) Mill. var. domestica (Borkh.) Mansf. cv. Cripps Pink], fruit were harvested from the same orchard each year from 2002 to 2005, at two or three maturity stages each year. Fruit were kept in air or controlled atmosphere (CA) storage (1.5- to 2-kPa O2 in combination with 1-, 3-, or 5-kPa CO2) at 0.5 °C. Additional subsets of fruit were exposed to 1 μL·L−1 1-methylcyclopropane (1-MCP) for 24 hours and dipped in 2200 μL·L−1 diphenylamine (DPA) for 5 min or held in air at 0.5 °C for 2 or 4 weeks before CA storage. Flesh browning was not seen in air-stored fruit but appeared in CA-stored fruit as soon as 2 months after harvest. Flesh browning incidence did not increase after longer storage times. Flesh browning increased with increasing CO2 concentration and decreasing O2 concentration in storage. 1-MCP did not significantly affect FB incidence, while delaying CA by 2 or 4 weeks reduced it. Diphenylamine eliminated FB incidence. When similar storage atmospheres were compared for the four seasons, FB incidence was high in 2002 and 2004 and low in 2003 and 2005. Concentrations of B, Ca, and Mg in apple flesh and seasonal field temperatures during the growing and harvest periods were related to FB incidence in 2002, 2003, and 2004 but not in 2005. The relationship of these pre- and postharvest factors to FB susceptibility are discussed.