A study of fruiting habits in pear trees

[摘要] ENGLISH ABSTRACT:The understanding of pear branching and bearing habits is required to optimise management practices.The objective of this study was to quantify the branching and bearing habits of pear cultivars underSouth African conditions of sub-optimal winter chilling.Two-year-old branches of Pyrus communis L. were classified into groups according to the proleptic(from dormant buds) branching habit. In Winter 1998 upright and flat, two-year-old branches wererandomly sampled from trees of seven pear cultivars, i.e., Forelle (on Quince A and BPI rootstocks),Abaté Fetel, Flamingo, Packham's Triumph, Golden Russet Bose, Rosemarie and Beurre D'Anjou (allon BPI rootstock). Laterals were classified according to length « lem, 1-5cm, 5-20cm and >20 cm)and position (distal to proximal quadrants on the two-year-old axis). The number of shoots per cm ofquadrant length, per length class for each cultivar was subjected to a cluster analysis, then a canonicaland a stepwise discriminant analysis. The cultivars were grouped into four groups from Group 1(Flamingo) which resembles a spurred growth habit with strong apical control, to Group 4 (Packham'sTriumph and Golden Russet Bose) which resembles a spreading growth habit and weak apical control.The bearing habits of the same pear cultivars were quantified. In Winter 1998 ten unpruned brancheswere tagged on trees of each of the seven cultivars. The description started with the development of themain fruiting branch, forming several leaves in the first year of growth (designated year Y), withmeristems developing in the leafaxils. In the following season (year Y+1), these axillary meristemshave five alternatives: to remain as a latent bud (L), to develop as a vegetative bud (V), to become aflower bud not setting fruit (F), to become a flower bud producing a fruit (P) or to abort and leave ascar (S). Each year the development of these axillary buds were observed and classified anew, givingrise to a sequence. Between 50% ('Forelle/QA') and 75% ('Rosemarie') of buds remained in thegrowing phase (comprising of V, F or P buds) during the years of monitoring. It was shown that thepredominant bud state in the growing phase was V. Although flower formation was low for all cultivarsthroughout the trial period, 'Packham's Triumph' and 'Rosemarie' displayed a relatively highproportion ofF and P buds in year Y+1. The latter two cultivars also displayed the bourse-over-boursebearing phenomenon (PP), producing flowers and fruit terminally on bourse shoots.Artificial extinction of reproductive buds was applied in Winter 1999 to individual branches of the pearcultivar Doyenne du Cornice. This pear variety bears on spurs and is prone to biennial bearing. Theobjective was to reduce the number of growing buds, thereby increasing the allocation of assimilates toremaining reproductive structures. Three thinning intensities, i.e. 0%, 33% and 66% removal ofreproductive buds and two methods, i.e. removal of proximal reproductive buds and removal ofreproductive buds situated distally on spurs (by means of cutting back) were utilised. Autonomy offruiting structures was not enhanced, but results warrant the repetition of this trial using whole trees asexperimental units.

[发布机构] Stellenbosch University