Rootstock Effects on the Flowering of `Delicious' Apple. I. Bud Development

Abstract

<jats:p>Floral development was studied in buds of `Starkspur Supreme Delicious' apple trees growing on B.9, M.26 EMLA, M.7 EMLA, P.18, and seedling rootstocks. In each of 3 years, buds were sampled from the previous years growth at intervals throughout the growing season and dissected to determine whether the apex was domed, indicating the start of floral development. Number of bud scales and true leaves increased during the early part of the growing season, but remained fairly constant beyond 70 days after full bloom. The type of rootstock did not affect the number of bud scales or transition leaves, and effects on true leaf numbers were small and inconsistent. Final bract number per floral bud was similarly unaffected by rootstock. The proportion of buds in which flowers were formed was influenced by rootstock in only one year of the study, which was characterized by high temperatures and low rainfall over the period of flower formation. Bracts were observed only in floral buds, and became visible after doming of bud apices had occurred. Flowers were formed during the first 20 days in August, regardless of rootstock or year. The appendage number of vegetative buds was constant from 70 days after full bloom until the end of the growing season, but the number of appendages in floral buds increased due to the continued production of bracts. The critical bud appendage number for `Starkspur Supreme Delicious' before flower formation was 20, and was stable among rootstocks and years. Buds with diameters above 3.1 mm were generally floral, but on this basis only 65% of buds could be correctly classified. Spur leaf number, spur leaf area, and spur leaf dry weight were not good predictors of floral formation within the spur bud.</jats:p>

Apple Rootstock-Induced Dwarfing is Strongly Influenced by Growing Environment

“…In general, monopodial axes on ' M793 ' had the highest frequency of sylleptic shoots and the lowest flowering frequency. Dwarfing rootstocks have been reported to increase precocity [23]. In our study, all trees flowered in spring of year two, indicating no rootstock effect on precocity.…”

Determination of floral initiation in Malus domestica: a novel morphogenetic approach

“…However, Hirst and Ferree (1995) reported that the apical doming, as the indicator trait for floral initiation, generally occurs between 85 and 109 DAFB. Hoover et al (2004) conducted a similar study to determine the effect of cultivar on the course of organogenesis on apple buds and also showed that doming occurs at 86 to 112 DAFB.…”

“…Characterisation of floral initiation seems to be ambiguous because of some uncertainties on description of flowering stages. Dencker and Hansen (1994) reported that the doming of apex in apple basically coincides with the cessation of shoot growth, which has also been considered as the first sign for floral initiation (Hirst and Ferree 1995). Foster et al (2003) quantitatively analysed the diameter of SAM over its developmental course and showed that the apex broadening happens prior to its doming.…”

Effect of Fruiting and Biennial Bearing Potential on Spur Quality and Leaf Gas Exchange in Apple

“…Measurements ANATOMICAL MEASUREMENTS. The following measurements were made on sampled spurs: 1) spur and bourse leaf number and leaf area (LI-3000; LI-COR, Lincoln, NE), 2) stomatal density, and 3) flower formation [examined under a dissecting microscope (SZ-STS; Olympus Corp., Center Valley, PA)] to determine flower formation for each bourse (Hirst and Ferree, 1995b).…”