Putrescine and spermidine preharvest treatments improve crop yield, resistance to rain-induced cracking and fruit quality traits in sweet cherries

Sweet cherry ( Prunus avium L.) is a fruit species of high commercial and nutritional value, although its production and marketing face numerous pre- and postharvest challenges, aggravated by extreme climatic events, such as heat waves or heavy rainfalls, which decrease crop yield and fruit quality. Polyamines, such as putrescine and spermidine, have been shown to improve stress tolerance and fruit quality. Therefore, this study evaluates the effect of preharvest applications of putrescine and spermidine on crop yield, tolerance to adverse weather conditions due to heavy rainfalls and fruit quality in 'Sunburst' and 'Skeena' sweet cherry cultivars during two consecutive seasons, 2022 and 2023. Preharvest applications of spermidine and putrescine at 0.01, 0.1 and 1 mM significantly increased yield in 2022 and reduced cracking induced by heavy rainfall occurring in 2023. In addition, significant improvements in fruit quality traits were observed in both cultivars and years, evidenced by an increase in fruit weight, firmness, red colour and titratable acidity, the highest effects being observed for 0.01 mM putrescine and spermidine. Moreover, total and individual phenolics and anthocyanins were also increased by polyamine treatments in both cultivars. Thus, preharvest polyamine treatments could be an innovative and useful tool to improve crop yield and quality properties in sweet cherry even under adverse climatic conditions as heavy rainfall, with beneficial effects for growers and consumers.