Postharvest kiwifruit (Actinidia chinensis cv. Hongyang) pulp is mainly composed of outer yellow-flesh (LR) and inner red-flesh (HR). However, information about the differences in coloration and fruit quality between these two parts are limited. In this study, widely targeted metabolomic, transcriptomic, and spatial metabolomic analyses were used to reveal the potential mechanism of coloration and fruit quality formation. The results show that a total of 1001 metabolites were identified in Hongyang kiwifruit, and the accumulation of 211 metabolites were significantly higher in the HR than LR, including 69 flavonoids, 53 phenolic acids, and 38 terpenoids. There were no significant differences in the content of citric acid, quinic acid, glucose, fructose, or sucrose between the LR and HR. These results were consistent with the results from the RNA-seq profile and spatial metabolomic analysis. In addition, a total of 23 key candidate genes related to flesh color and fruit quality formation were identified and validated by qRT-PCR analysis. This study provides a theoretical basis for elucidating the underlying mechanism of the formation of kiwifruit flesh color and fruit quality.

为明确CPPU处理对猕猴桃果实生长发育及采后品质的影响,以猕猴桃黄肉品种"金艳"为试验材料,于盛花后30 d采用10 mg/L CPPU进行幼果浸果处理,自然生长果实为对照,测定生长发育期、常温处理(20℃)与低温贮藏(1℃)的果实品质指标动态变化.结果表明:(1)与对照相比,10 mg/LCPPU处理在采收时明显提高了果实内外品质指标,促进了果实提早成熟.其中单果质量与纵横侧径分别提高了 11.35％、7.20％、6.21％与7.08％;蔗糖含量提高了 12.93％;可溶性固形物、干物质与果糖含量高于对照,但差异不显著.(2)在20℃常温处理下,经CPPU处理的果实采后达到可食状态时可溶性固形物、果糖、蔗糖含量比对照显著提高了 10.74％、3.34％、4.42％;同时促进了呼吸高峰的提前,缩短了货架期.(3)在1℃低温贮藏末期,经CPPU处理的果实采后可溶性固形物、果糖、葡萄糖含量比对照显著提高了 13.11％、7.23％、11.11％,且果实硬度下降加快,缩短了采后贮藏保鲜期.综上所述,10 mg/L CPPU处理显著提高了果实单果质量,提升果实内在品质,同时加快了果实成熟进程,缩短了果实成熟期及采后贮藏保鲜期.

Iron is a trace element essential for normal plant life activities and is involved in various metabolic pathways such as chlorophyll synthesis, photosynthesis, and respiration. Although iron is highly abundant in the earth’s crust, the amount that can be absorbed and utilized by plants is very low. Therefore, plants have developed a series of systems for absorption, transport, and utilization in the course of long-term evolution. This review focuses on the findings of current studies of the Fe 2+ absorption mechanism I, Fe 3+ chelate absorption mechanism II and plant-microbial interaction iron absorption mechanism, particularly effective measures for artificially regulating plant iron absorption and transportation to promote plant growth and development. According to the available literature, the beneficial effects of using microbial fertilizers as iron fertilizers are promising but further evidence of the interaction mechanism between microorganisms and plants is required.

Kiwifruit is a climacteric fruit, in which the accumulation of flavor substances mainly occurs at the postharvest ripening stage. However, the dynamic changes in metabolite composition remain poorly understood. Here, targeted multi-platform metabolome analysis based on GC-MS and UPLC-MS/MS and enzyme activity analysis were performed at different postharvest ripening stages of kiwifruit. A total of 12 soluble sugars and 31 organic acids were identified. The main soluble sugars are sucrose, glucose and fructose, which exhibited similar variation tendencies along with the extension of ripening. The main organic acids are citric acid, quinic acid and malic acid, which showed different variation patterns. A total of 48 energy metabolites were identified, which were classified into two groups based on the content variation. The content of substances related to the respiratory metabolic pathway decreased gradually along with postharvest ripening, and there was obvious accumulation of downstream products such as amino acids at the late ripening stage. A total of 35 endogenous hormones were identified, among which seven cytokinins were highly accumulated at the later stage of softening. We further investigated the dynamic changes in the activities of 28 ripening-related enzymes. As a result, the activities of 13 enzymes were highly correlated with changes in starch, total pectin, and soluble sugars, and those of seven enzymes were closely associated with the change in firmness. In conclusion, this study comprehensively describes the dynamic changes in soluble sugars, organic acids, hormones, energy substances, and ripening-related enzyme activities during kiwifruit postharvest ripening, and provides a theoretical basis for the postharvest quality improvement of kiwifruit.