Acharya Tej P, Nambeesan Savithri U
Department of Horticulture, University of Georgia, 1111 Miller Plant Sciences Building, Athens, GA, 30602, USA.
U.S. Department of Agriculture, Agriculture Research Service, U.S. Horticultural Research Laboratory, Citrus and Other Subtropical Products Research Unit, 2001 South Rock Road, Fort Pierce, 34945, FL, USA.
BMC Plant Biol. 2025 Jun 5;25(1):766. doi: 10.1186/s12870-025-06799-x.
Fruit ripening is a coordinated process that leads to an increase in sugars, decrease in acids and accumulation of pigments. Blueberry fruit exhibit an atypical climacteric ripening behavior. These fruit display an increase in respiration and ethylene production during ripening, however ethylene synthesis is developmentally regulated. In this study, the effect of ethylene on blueberry fruit ripening was investigated via preharvest applications of ethylene-releasing plant growth regulators (PGRs), ethephon and 1-aminocyclopropane 1-carboxylic acid (ACC), in one southern highbush cultivar, Miss Lilly in 2019, and two rabbiteye cultivars, Premier and Powderblue in 2019 and 2020. Further, the effects of these two PGRs on fruit metabolism during ripening in the two rabbiteye cultivars, and postharvest fruit quality in all three cultivars were evaluated.
Both PGRs increased ethylene evolution within 1-3 days after treatment (DAT). Ethephon and ACC applications increased the rate of ripening within 5 DAT in all cultivars, and increased ripe (blue) fruit by up to 35% and 29%, respectively between 7 to 10 DAT compared to the control. Metabolite analysis revealed that PGR treatments resulted in an immediate, but transient increase in sucrose, glucose and fructose, in 'Premier' at 3 DAT. Malate decreased at 3 DAT in response to both PGR treatments in 'Premier', and at 5 DAT in ethephon treatment in both cultivars. A rapid increase in the concentration of multiple anthocyanins was noted at 3 DAT in response to both PGRs in 'Premier' and 'Powderblue'. Gene expression analysis revealed an increase in transcript abundance of VACUOLAR INVERTASE (vINV) and multiple anthocyanin biosynthesis genes between 1 and 3 DAT after PGR treatments in both cultivars, supporting the metabolite changes. However, the alteration in fruit metabolite concentrations were not sustained, and similar in PGR-treated fruit compared to the control in ripe fruit harvested at 10 DAT. Postharvest fruit quality attributes, such as firmness, total soluble solids, titratable acidity, and visual quality, were not consistently affected by the PGR applications compared to control treatments across all cultivars. A decrease in fruit weight was noted, although not consistently, in response to PGR treatments.
Overall, this study demonstrates that ethylene plays a crucial role in promoting ripening via rapid and transient stimulation of sugar, acid and anthocyanin metabolism. The promotion of fruit ripening by ethylene-releasing PGRs can lead to minimal but inconsistent changes in fruit quality attributes during postharvest storage.
果实成熟是一个协调的过程，会导致糖分增加、酸度降低和色素积累。蓝莓果实表现出非典型的跃变型成熟行为。这些果实成熟期间呼吸作用和乙烯产量增加，然而乙烯合成受发育调控。在本研究中，通过在2019年对南方高丛品种“莉莉小姐”以及2019年和2020年对两个兔眼品种“总理”和“粉蓝”进行采前施用乙烯释放型植物生长调节剂（PGR）乙烯利和1-氨基环丙烷-1-羧酸（ACC），研究了乙烯对蓝莓果实成熟的影响。此外，评估了这两种PGR对两个兔眼品种果实成熟期间代谢的影响以及对所有三个品种采后果实品质的影响。
两种PGR在处理后1 - 3天内均增加了乙烯释放量。乙烯利和ACC处理在所有品种中均在处理后5天内提高了成熟速率，与对照相比，在处理后7至10天成熟（蓝色）果实分别增加了35%和29%。代谢物分析表明，PGR处理导致“总理”品种在处理后3天蔗糖、葡萄糖和果糖立即但短暂增加。在“总理”品种中，两种PGR处理均使苹果酸在处理后3天减少，在两个品种的乙烯利处理中，苹果酸在处理后5天减少。在“总理”和“粉蓝”品种中，两种PGR处理均使多种花青素浓度在处理后3天迅速增加。基因表达分析表明，两个品种在PGR处理后1至3天液泡转化酶（vINV）和多个花青素生物合成基因的转录丰度增加，支持了代谢物变化。然而，果实代谢物浓度的变化并未持续，与对照相比，在处理后10天收获的成熟果实中，PGR处理的果实代谢物浓度变化相似。与对照处理相比，所有品种的PGR处理对采后果实品质属性如硬度、总可溶性固形物、可滴定酸度和外观品质的影响并不一致。尽管并非始终如此，但PGR处理导致果实重量下降。
总体而言，本研究表明乙烯通过快速和短暂刺激糖、酸和花青素代谢在促进成熟中起关键作用。乙烯释放型PGR促进果实成熟会导致采后贮藏期间果实品质属性出现最小但不一致变化。
