Use of Biostimulants for Organic Apple Production: Effects on Tree Growth, Yield, and Fruit Quality at Harvest and During Storage.

The experiment was conducted during two consecutive seasons (years 2016 and 2017) in an organic apple orchard of the cultivar Jonathan. Several biostimulants were tested (10 in total), including humic acids, macro and micro seaweed extracts, alfalfa protein hydrolysate, amino acids alone or in combination with zinc, B-group vitamins, chitosan and a commercial product containing silicon. Treatments were performed at weekly intervals, starting from the end of May until mid-August. The macroseaweed extract was effective in stimulate tree growth potential in both years, as shown by a significantly larger leaf area (+20% as compared to control) and by an higher chlorophyll content and leaf photosynthetic rate in year 2016. As for the yield performances and apples quality traits at harvest (average fruit weight, soluble solids content, titratable acidity, and flesh firmness), they were generally affected by the different climatic conditions that characterized the two growing seasons (year 2017 being characterized by higher maximal and average temperatures and by limited rainfalls at the beginning of the season). Treatments with macroseaweed extract, B-group vitamins and alfalfa protein hydrolysate were able to significantly improve the intensity and extension of the red coloration of apples at harvest. Correspondingly, the anthocyanin content in the skin of apples treated with the same biostimulants resulted significantly higher than control, highlighting the potential influence of these substances on the synthesis of secondary metabolites in apple. The incidence of physiological disorders was also monitored during apple storage period. Amino acids plus zinc application was effective in reducing (more than 50%) the incidence of the "Jonathan spot," the main post-harvest disorder for this cultivar.

Effect of the use of anti-hail nets on codling moth (Cydia pomonella) and organoleptic quality of apple (cv. Braeburn) grown in Alto Adige Region (northern Italy).

BACKGROUND: The anti-hail nets are widely used to protect apple fruit against hailstorms and hail damage. They can have also beneficial effects against pests in apple orchards, in particular codling moth (Cydia pomonella). However, covering the trees with anti-hail nets can modify the orchard microclimate and reduce the interception of light, thus potentially causing negative consequences on the organoleptic quality of apple fruits. RESULTS: A consistent reduction of the percentage of apple fruits infested by codling moth was registered as a result of the use of anti-hail nets during two consecutive harvest years. Their use did not affect fruit maturity, but reduced the skin colour, sugar content, pulp total phenol content, volatile compound composition and sensory characteristics. However, the results were inconsistent over the two years apart for total phenols, formation of two volatile compounds (butyl and hexenyl acetate, the first being one of the main odorants in most apple cultivars), sensory attributes of 'flavour of lemon' and 'juiciness'. For these parameters, the fruits from plots where the trees were not covered showed higher values than those from plots where anti-hail nets were used. CONCLUSIONS: The use of anti-hail nets was effective in preventing the attack of codling moth to apple fruits, suggesting their use in organic management where conventional insecticides are prohibited. Under the conditions tested, anti-hail nets showed a negative effect on some of the quality characteristics measured on apple fruits, which could influence consumer acceptability.

Impact of innovative controlled atmosphere storage technologies and postharvest treatments on volatile compound production in cv. Pinova apples.

Organically grown apples cv. Pinova harvested at two different dates were stored at 1.3 degrees C for up to 4 months in air, up to 7 months in ULO (1.5 kPa of O(2) and 1.3 kPa of CO(2)) and in dynamic controlled atmosphere (DCA) conditions (0.4-0.6 kPa of O(2) and 0.6-0.8 kPa of CO(2)); the DCA storage method involved the use of a chlorophyll fluorescence monitoring system in order to detect low-O(2) stress in apples and to allow for the dynamic adaptation of storage atmosphere to O(2) levels that were lower than in ULO but still tolerated by fruits. A postharvest 1-MCP treatment (for 24 h at 1.3 degrees C) and a hot water treatment (for 180 s at 50 degrees C) were also tested on apples stored afterward in ULO and air, respectively. Volatile compounds isolated from the pulp of fruits were measured after 4 and 7 months, just upon removal from storage and after 11 days at 22 degrees C. Total amount of aroma compounds detected in apples stored in DCA was markedly higher (from 2- to 4-fold) than in fruits exposed to 1-MCP + ULO but, at most sampling times, significantly lower than in ULO fruits. Moderate differences in storage atmosphere composition between ULO and DCA significantly affected both total amount and profile of volatile esters. Analogous effects were observed on the alcohol precursors of the main esters. Exposure to 1-MCP inhibited biosynthesis of straight-chain esters more than that of branched-chain esters. The hot water treatment did not seem to produce marked changes in volatile composition after four months of air storage, except for a sharp accumulation of aldehydes during the shelf-life time. DCA storage technology, besides avoiding any chemical treatment, can preserve apple aroma compounds better than 1-MCP + ULO during long-term storage.