Liu Xin-Sheng, Luo Ye-Cheng, Wang Si-Wei, Wang Hui-Cong, Harpaz-Saad Smadar, Huang Xu-Ming
Guangdong Litchi Engineering Research Center, College of Horticulture, South China Agricultural University, Guangzhou, China.
Plant Protection Research Institute, Guangdong Academy of Agricultural Science, Guangzhou, China.
Front Plant Sci. 2022 Mar 4;13:829635. doi: 10.3389/fpls.2022.829635. eCollection 2022.
Litchi is a highly perishable fruit. Ripe litchi fruit loses quality quickly as they hang on tree, giving a very short hanging life and thus harvest period. This study attempted to explore the roles of cytokinin in regulating fruit ripening and senescence of litchi and examine the possibility of applying cytokinin in "on-tree storage" of the fruit. Exogenous cytokinin, forchlorfenuron (CPPU), was applied at 20 mg L 7 weeks after full bloom on litchi ( cv. Feizixiao) fruit clusters. Color parameters, chlorophylls, anthocyanins, fruit and fruit part weights, total soluble solutes (TSSs), soluble sugars, organic acids, non-anthocyanin flavonoids, ethanol, and also CPPU residue in fruit were traced. CPPU residue was higher but decreased faster in the pericarp than in the aril, where it maintained < 10 μg kg. CPPU had no significant effect on fruit weight but tended to increase pericarp weight. The treatment suppressed chlorophyll loss and anthocyanin accumulation in the pericarp, increased non-anthocyanin flavonoids in the aril, but had no significant effects on non-anthocyanin flavonoids in the pericarp and total sugar and organic acids in the aril. As the commercially ripe fruit hanged on tree, TSSs, total sugar, and sucrose decreased with ethanol and acetic acid accumulation in the aril. CPPU significantly suppressed the loss of sucrose and total sugar and the accumulation of ethanol and acetic acid in the aril and inhibited malondialdehyde accumulation in the pericarp of the overripe fruit. Soluble invertase, alcohol dehydrogenase, and pyruvate decarboxylase (PDC) activity and gene expression in the aril were downregulated by CPPU. The results suggest that cytokinin partially suppresses the ripening process in litchi and is effective to slow quality loss in the overripe fruit on tree.
荔枝是一种极易腐烂的水果。成熟的荔枝果实挂在树上时品质迅速下降，挂果寿命和收获期都很短。本研究试图探讨细胞分裂素在调控荔枝果实成熟和衰老中的作用，并研究在果实“树上贮藏”中应用细胞分裂素的可能性。在荔枝（品种：妃子笑）果实簇盛花7周后，以20 mg/L的浓度喷施外源细胞分裂素氯吡脲（CPPU）。对果实的颜色参数、叶绿素、花青素、果实及各部分重量、总可溶性固形物（TSS）、可溶性糖、有机酸、非花青素类黄酮、乙醇以及果实中的CPPU残留量进行了追踪。CPPU在果皮中的残留量较高，但下降速度比假种皮快，假种皮中的残留量维持在<10μg/kg。CPPU对果实重量无显著影响，但有增加果皮重量的趋势。该处理抑制了果皮中叶绿素的损失和花青素的积累，增加了假种皮中非花青素类黄酮的含量，但对果皮中非花青素类黄酮以及假种皮中的总糖和有机酸无显著影响。随着商业成熟的果实挂在树上，假种皮中的TSS、总糖和蔗糖含量下降，同时乙醇和乙酸积累。CPPU显著抑制了假种皮中蔗糖和总糖的损失以及乙醇和乙酸的积累，并抑制了过熟果实果皮中丙二醛的积累。CPPU下调了假种皮中可溶性转化酶、乙醇脱氢酶和丙酮酸脱羧酶（PDC）的活性及基因表达。结果表明，细胞分裂素可部分抑制荔枝的成熟过程，对减缓树上过熟果实的品质损失有效。
