Exploring Carbohydrate Concentration Fluctuations in Pistachio (Pistacia vera L. cv Uzun) for Deeper Insights into Alternate Bearing Patterns

Alternate bearing (AB) is of great importance in horticulture and leads to fluctuations in yield variation. Although AB is a natural phenomenon to optimize resource allocation and improve crop productivity and profitability in plants, understanding the factors that influence AB can help in implementing effective management strategies to reduce the negative effects and promote consistent and sustainable production. This study aimed to investigate the variation in carbohydrate levels in various tissues of both bearing and non-bearing pistachio (Pistacia vera L. cv Uzun) trees during different periods of growth development in two consecutive years to gain a deeper understanding of their potential contribution to AB. Twelve 34-year-old pistachio trees, consisting of six "ON" and six "OFF" year trees, were accidentally selected from a pistachio orchard. The "OFF" year trees were induced two years before sampling to be in the "OFF" year state by artificially removing flower buds. Sucrose was the main soluble sugar in the different parts of the pistachio tree studied. In general, the amount of sugar was higher in the non-bearing year than in the bearing year. It was found that non-structural carbohydrates of trees decreased between June and July, resulting in flower buds to abscise. The amount of carbohydrates decreased during nut development in "ON" trees, indicating the possible role of carbohydrates in AB.