Effects of Ethephon and Abscisic Acid Application on Ripening-Related Genes in 'Kohi' Kiwifruit (Actinidia chinensis) on the Vine

The effects of ethephon and abscisic acid (ABA) application on ripening-related genes of pre-harvest 'Kohi' kiwifruit (Actinidia chinensis) were studied to clarify the possibility of the fruit ripening on the vine. The fruits were treated on the vine at mature stage with 250 µL⋅L−1 ethephon or 100 µmol⋅L−1 ABA, and the expression levels of chlorophyll synthase (AcCLS), chlorophyllase1 (AcCLH1), polygalacturonase (AcPG), expansin (AcEXP), β-amylase (Acβ-AM), sucrose synthase (AcSUSY), MADS-box SEPALLATA4/RIPENING INHIBITOR-like (AcSEP4/RIN) and FRUITFUL-like (AcTDR4/FUL) genes were analyzed. The expression levels of AcPG, AcEXP, Acβ-AM, and AcSUSY increased in the ethephon-treated fruit, but those of AcCLH1 at 6 and 9 days after treatment and AcCLS decreased. Moreover, the expression levels of AcSEP4/RIN and AcTDR4/FUL, the latter of which is associated with ethylene biosynthesis, were higher in the ethephon-treated fruit. The expression level of each gene in ABA-treated fruit was not significantly different from that of the untreated control. The results suggest that ethephon application increases the expression levels of AcPG, AcEXP, Acβ-AM, AcSUSY, AcSEP4/RIN, and AcTDR4/FUL in 'Kohi' kiwifruit on the vine.