Changes in the level of endogenous free polyamines and fruit development during bearing and non-bearing years in seedless barberry ( Berberis Vulgaris L.)

To realize the relationship between changes in polyamines (PAs) and barberry fruit growth, the free endogenous PAs of the fleshy part (pericarp) of fruit were measured. To this end, sampling was performed in three replications in six fruit development stages, including 35, 54, 71, 98, 125 and 155 days after full bloom (DAFB) during the ON (2018) and OFF (2019) year. Four growth stages (S1–S4) were observed in barberries. The fruit growth curve in seedless barberries was identified as double sigmoid. The results showed that despite the similarity in the processing of changes in the level of PAs and gaining fresh weight in both years, a significant difference was observed throughout the sampling stages. In both years, differences in increasing the length and diameter of the fruit after the first and second stages of sampling were observed, and a significant difference was found between the sampling stages and the fruiting years by the end of growth. Total PAs content in the ON year was higher than the OFF year. In the OFF year, the decreased spermidine concentration at 54th DAFB was found to be responsible for the abscission of berries formed at this stage. In pericarp, the level of putrescine was higher during early development than the other PAs in both years and then gradually decreased. Despite the relationship between increased spermidine and the length and diameter of berries, fresh fruit weight and soluble solids, the results of this study cannot exactly identify a specific polyamine responsible for changes in the traits of barberry fruit. Significance of the study What was already known about this subject? Knowledge of fruit growth patterns and polyamine functions existed in other fruit crops, but not in seedless barberry. What is the new finding? The fruit growth curve and polyamine levels were characterized for the first time in seedless barberry, and spermidine was identified as a factor involved in fruit drop. What are the expected impacts on horticulture? These findings improve the understanding of fruit development and fruit drop in seedless barberry and may help develop management strategies to reduce fruit abscission and improve yield and fruit quality.