Data_Sheet_1_Use of Biostimulants for Organic Apple Production: Effects on Tree Growth, Yield, and Fruit Quality at Harvest and During Storage.docx

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.

本试验于2016与2017连续两个生长季，在一片种植乔纳森（Jonathan）品种的有机苹果园中开展。试验共测试10种生物刺激素，涵盖腐殖酸、大型与微型海藻提取物、苜蓿蛋白水解物、单独或与锌复配的氨基酸、B族维生素、壳聚糖以及一款含硅商用产品。处理于5月末至8月中旬期间每周开展一次。大型海藻提取物在两个生长季均能有效提升果树生长潜力：2016年的试验结果显示，其可显著增大叶面积（较对照组提升20%），同时提高叶片叶绿素含量与光合速率。关于收获期的产量表现与苹果品质性状（平均单果重、可溶性固形物含量、可滴定酸度及果肉硬度），二者总体受两个生长季的不同气候条件影响：2017年生长季前期最高气温与平均气温均更高，且降雨量偏少。施用大型海藻提取物、B族维生素及苜蓿蛋白水解物的处理，可显著提升收获期苹果果皮红色着色的强度与面积。相应地，经上述三类生物刺激素处理的苹果果皮花青素含量显著高于对照组，表明这些物质可对苹果次生代谢产物的合成产生潜在调控作用。试验同时监测了苹果贮藏期的生理病害发生情况：施用氨基酸与锌复配制剂的处理可有效降低乔纳森斑点病（Jonathan spot）——该品种主要的采后生理病害——的发生率，降幅超过50%。