Residue Analysis and the Effect of Preharvest Forchlorfenuron (CPPU) Application on On-Tree Quality Maintenance of Ripe Fruit in “Feizixiao” Litchi (Litchi chinensis Sonn.)

Abstract

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−1 7 weeks after full bloom on litchi (Litchi chinensis 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−1. 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.

Genome-Wide Identification and Expression Analysis of m6A Writers, Erasers, and Readers in Litchi (Litchi chinensis Sonn.)

“…This suggested that higher m6A modification levels induced by a relatively higher expression of LcMTA_2 and lower expression of LcALKBH10A might be the important factors for the delay of the maturation of the ‘Feizixiao’ variety induced by exogenous CPPU. CPPU is an inhibitor of ABA biosynthesis, and it had been reported that the application of exogenous CPPU had no significant effect on fruit weight, total sugar, and organic acids, but it did repress the coloration conspicuously by suppressing chlorophyll loss and anthocyanin accumulation in the fruit of the ‘Feizixiao’ variety [ 38 ]. ABA was considered as the critical hormone related to anthocyanin accumulation and chlorophyll loss during litchi fruit ripening [ 19 , 24 , 36 , 39 ], and the fruit of the ‘Feizixiao’ variety that appeared in the ‘stay green’ phenomenon (an uneven pigmenting problem) was considered to be mainly caused by the insufficient anthocyanin content induced by the relative low ABA accumulation during fruit coloration, which result in could not cover up the chlorophyll related determining substances of background color [ 35 ].…”

A Magnetic-Bead-Based Immunoassay with a Newly Developed Monoclonal Antibody for Rapid and Highly Sensitive Detection of Forchlorfenuron

“…Forchlorfenuron (CPPU) is a synthetic plant growth regulator with strong cytokinin-like activity [ 1 ]. It has become a popular agrochemical to boost size and improve the quality of fruit [ 2 , 3 ]. CPPU has been extensively used due to the growing market demand for high-quality fruits, which poses a potential health risk to consumers exposed to CPPU from food ingestion.…”