Will secondary buds be savior to pecan spring freeze damages?

Pecan, Carya illinoiensis (Wangenh.) K. Koch, is the main tree crop produced in Oklahoma, USA, and the state ranks in the top 5 pecan producers in the United States. However, pecan trees in Oklahoma frequently suffer from spring freeze. Our previous research revealed at 4°C for 4 h both male and female flowers were observed wilted or damaged. Fortunately, the secondary buds of some pecan cultivars will develop into healthy flowers if the primary buds are impaired, which functions as a fail-safe to guarantee yield. Previous reports demonstrated some other cultivars set abnormal flowers, or failed to produce flowers from secondary buds. In this research, we collected three pecan cultivars ‘Pawnee’, ‘Kanza’, and ‘Maramec’ shoots with buds/flowers at different growth stages: stage 1 outer bud scale shed stage, stage 2 inner bud scale shed stage, and stage 3 early bloom stage. The sproutability of secondary buds was observed with a pre-treatment of -6°C for 4 and 8 h to kill the primary buds. Our results indicated that the number of branches with secondary buds, and the bud/flower stage when primary buds were killed off, varied among cultivars. ‘Kanza’ and ‘Pawnee’ have a higher ability to produce secondary buds when primary buds fail in stage 1; while ‘Maramec’ produces more secondary buds in stage 2. The shoots with secondary buds were also collected for further carbohydrate analysis. The correlations between the bloom of secondary buds and carbohydrate levels will be studied.