Analysis of bud and sylleptic shoot distribution along 1-year-old shoots of hazelnut (Corylus avellana)

Tree architecture is important because it influences the light interception in the canopy. It determines where the different organs (e.g., leaves and fruits) are borne and, consequently, the source-sink interactions on the tree. Tree architecture directly affects the yield of filbert (Corylus avellana L.). In winter, four main structures are detectable on one-year-old shoots: mixed buds, which, in summer, will bear nuts; vegetative buds, which, in spring, will sprout into new shoots; blind nodes, which do not have any bud; and sylleptic shoots, which bear the male inflorescences in the apical position. Our hypothesis was that the distribution of buds, among one-year-old shoots, followed a specific pattern. Moreover, we hypothesized that this pattern could change with age or because of the rootstock (C. colurna seedlings). We designed three trials (1: young trees own-rooted; 2: young trees grafted, 3: old trees own-rooted) and we sampled 120 one-year-old shoots of ‘Tonda di Giffoni’. Our study highlights four regions among one-year-old shoots: the first part of the shoot was characterized by blind nodes, followed by a region of the shoot with sylleptic shoots, and then, in the median part of the shoots, a prevalence of mixed buds followed by vegetative buds in the distal part of the shoot. In grafted trees, the region with mixed buds was longer than in own-rooted trees and the last region had more vegetative buds. This led to longer new shoots in the subsequent year and, thus, a reduction of the aging phenomenon. Huge differences were highlighted from the third trial when compared to the first. Indeed, the first (blind node) and last (vegetative buds) regions were substituted by the presence of sylleptic shoots. Aging causes a reduction in shoot length and, consequently, a decrease in vegetative and mixed buds. This study could be used to guide managerial practices, such as pruning, in a more physiological and precise fashion, to reduce the aging of the tree without losing productivity.

Francesca Grisafi won the ISHS Young Minds Award for the best oral presentation at the X International Congress on Hazelnut in USA in September 2022.

Francesca Grisafi, Department of Sustainable Crop Production, Università Cattolica del Sacro Cuore, Via Emilia Parmense 84, 29122 Piacenza, Italy, e-mail: francesca.grisafi1@unicatt.it

The article is available in Chronica Horticulturae