Unraveling the multifaceted role of N-(2-chloro-4-pyridyl)-N′-phenylurea in regulating kiwifruit post-ripening quality via sugar and cell wall metabolism

Although N-(2-chloro-4-pyridyl)-N′-phenylurea (CPPU) is widely used for kiwifruit enlargement, its effects on post-ripening quality remain unclear. This study integrated physiochemical and multi-omics analyses to investigate the impacts of CPPU on the quality of kiwifruit at harvest and after post-ripening. CPPU promoted fruit enlargement by expanding parenchyma cells, particularly small parenchyma cells, and enhanced uniformity in fruit appearance. CPPU increased pigment content, but suppressed starch accumulation resulting in lower total sugars in post-ripening fruit. Notably, CPPU might accelerate fruit softening by enhancing the activities of polygalacturonase, pectin lyase, and pectin methylesterase, as well as impairing the antioxidant system. CPPU also caused the loss of typical volatile esters (including benzoic acid ethyl ester and ethyl hexanoate), resulting in the dilution of flavor profiles in post-ripening fruit. Multi-omics analysis revealed that CPPU-mediated regulation of ripe fruit quality may be related to two aspects: inhibition of phenylpropanoid biosynthesis and the regulation of amino sugar and nucleotide sugar metabolism. These findings provide new insights into the potential mechanisms by which CPPU regulates the quality of ‘Cuixiang’ kiwifruit.