2019 ASHS Annual Conference

Flower longevity is an important characteristic of floriculture crops. When petals senesce, ornamental plants lose their aesthetic and economic value. However, the regulatory mechanisms involved in flower petal senescence are complex and not well understood. Although nutrient mobilization is considered important in the regulation of flower petal senescence, there is a lack of genetic evidence to substantiate the roles of nutrient mobilization-related genes during this process. A recent transcriptomic study of Petunia × hybrida corollas identified nutrient mobilization-related autophagy (ATG) and nuclease (NUC) genes that are differentially regulated during petal senescence. We hypothesize that regulating the expression levels of these genes will affect the longevity of petunia flowers, with varying effects under high and low nutrient conditions. To test this hypothesis, individual genes were knocked down using virus-induced gene silencing (VIGS) in Petunia × hybrida ‘Picobella Blue’. The ATG-silenced plants were fertilized with 50 or 250 ppm N from 15-5-15 fertilizer at every irrigation, and the NUC-silenced plants were given nutrient solutions with normal or low phosphate levels. Our results indicate that the silencing of NUC1resulted in delayed flowering and early senescence, and the silencing of three individual ATGscaused changes in flowering time, flower longevity, and flower number in petunia under different fertility levels. The genes identified in this study will be further tested using stable genetic engineering and genome editing. The results of this project will be fundamental for future studies of flower petal senescence and will provide genetic information for future floriculture crop improvement.