How does peach fruit set on sylleptic shoots borne on epicormics compare with fruit set on proleptic shoots?

摘要

Proleptic and epicormic shoots on peach (Prunus persica) have different growth characteristics that have management implications for peach production. Proleptic shoots arise from buds after a dormant period, and are made up mostly of preformed nodes and organs which exist in dormant buds and extend after bud-break. Epicormic shoots (also known as 'water sprouts') arise from preventitious meristems without the formation of a bud and are characterized by vigorous, upright growth. They are usually stimulated by heavy pruning, branch breaking, or drastic branch bending and exhibit low correlative inhibition which results in many lateral sylleptic shoots. Because lateral meristems that form sylleptic shoots have no preformed organs, sylleptic shoots are made entirely of neo-formed growth. Epicormic shoots, in contrast to the determinate nature of proleptic shoots, continue growing until environmental conditions become unfavorable; however this study indicates that sylleptic shoots on epicormic shoots appear to be limited to similar numbers of nodes as proleptic shoots even though they may grow as late as 180 days after bud-break. Both proleptic, and sylleptic shoots borne on epicormic shoots, have flower buds but it is not clear if the flower buds on both types of shoots are equally capable of setting fruit. The objective of this research was to compare flowering and fruit set on proleptic and sylleptic shoots on four different peach cultivars with different times of fruit maturity. Differences in flower bud density, flowering, initial fruit set and final fruit set were observed between shoot types and among cultivars. Flower bud density was higher on proleptic shoots than sylleptic shoots on all cultivars and there was greater flower bud drop prior to bloom on sylleptic shoots of three of the cultivars. Initial percent fruit set of buds that flowered was very high (&80%) on both shoot types of all cultivars but percent final fruit set was higher on sylleptic shoots of two of the cultivars. On average, proleptic shoots of a specific cultivar bore more fruit per shoot than sylleptic shoots of the same cultivar and the two earliest maturing cultivars tended to bear more fruit per respective shoot type than the two later maturing cultivars.