ASHS 2024 Conference

Pecan growers face significant challenges in protecting their crops from the spring freezes that devastate yields. Conventional freeze protection methods are impractical for the large, tall trees. This study investigated the dynamics of the secondary bud break in pecan trees, a mechanism that ensures yield when primary buds are damaged. In three pecan cultivars ('Pawnee,' 'Kanza,' and 'Maramec') we characterized the sprouting potential of secondary buds after the primary buds were cold damaged. Primary bud shoots were collected at three different bud growth stages: outer bud scale shed stage, inner bud scale shed stage, and early bloom stage. The shoot samples held at 6°C to terminate primary buds’ growth. The cold treated shoots were then held in growth chambers set to mimic spring humidity, temperature, and light conditions. The percentage of branches with secondary bud break was recorded. The carbohydrate levels (sugar and starch) were measured in the apical shoots treated at the outer bud scale shed stage. The results showed variation among cultivars in the number of shoots with secondary buds and the stage at which primary buds were terminated. The ‘Kanza’ and ‘Pawnee’ cultivars produced more secondary buds when the primary buds were cold damaged in the outer bud scale shed stage. The ‘Maramec’ cultivar produced more secondary buds when the primary buds were cold damaged in the inner bud scale shed stage. The A carbohydrate analysis of the three cultivars demonstrated a correlation between successful secondary bud break and elevated carbohydrate levels in the one-year-old shoots. Cultivars with higher secondary bud break rates, 'Kanza' and 'Pawnee', had higher carbohydrate levels than 'Maramec.' These findings suggest that higher carbohydrate levels in one-year-old shoots facilitate successful secondary bud break following spring freeze damage to primary buds. This research suggests developing production practices to improve tree carbohydrate levels in the late summer and fall could potentially protect pecan production from spring freeze damage.