Auxin signalling regulation during induced and parthenocarpic fruit set in zucchini

Fruit set and fruit development can be limited due to ineffective pollination in off-season crops of Cucurbita pepo. To avoid this problem, parthenocarpy, the natural or artificial fruit development without fertilization, is required. The application of synthetic growth regulators is a common practice for inducing stimulative parthenocarpy in zucchini cultivars, but this method increases production costs and may cause other fruit defects. The disadvantages associated with this can be overcome through the use of vegetative parthenocarpic cultivars, which allow fruit set without any external stimuli. Three zucchini cultivars have been studied and differences have been found in parthenocarpic fruit development. Ethylene release of unpollinated fruit has corroborated the parthenocarpic fruit development. Vegetative parthenocarpy was observed in the Whitaker cultivar. Furthermore, the involvement of the auxin signalling pathway in controlling fruit set and parthenocarpy have been studied. Transcriptome analysis of auxin signalling genes, CpARF8, CpIAA9 and CpTIR1, have shown tissue-specific expression and have revealed a decrease in the expression levels of these genes in pollinated fruits after the fertilization signal, indicating their role in the transition from ovary to fruit. Nevertheless, it has also been shown that expression of these genes can be different between parthenocarpic cultivars.