Rootstock Effects on Shoot Morphology and Spur Quality of `Delicious' Apple and Relationships with Precocity and Productivity

Abstract

<jats:p>Two-year-old branch sections of `Starkspur Supreme Delicious' apple <jats:italic>(Malus domestics</jats:italic> Borkh.) trees growing on 17 rootstock were studied over 6 years to determine the effects of rootstock on shoot morphology and spur quality and describe how these factors may be related to precocity and productivity. Shoot length was affected by rootstock and was positively related to trunk cross-sectional area within each year, but the slope of the regression line decreased as trees matured. The number of spurs on a shoot was largely a product of shoot length. Spur density was inversely related to shoot length, where rootstock with longer shoots had lower spur densities. Flower density was not related to spur density, and shoot length only accounted for a minor part of the variation in flower density. The proportion of spurs that produced flowers was closely related to flower density, indicating that rootstock influence flower density by affecting the development of individual buds rather than by the production of more buds. More vigorous rootstock generally had spurs with larger individual leaves and higher total leaf area per spur, but fewer spur leaves with lower specific leaf weights. More precocious rootstock were also more productive over a 10-year period when yields were standardized for tree size. Tree size was the best indicator of precocity and productivity, which could be predicted with a high degree of certainty as early as the 4th year.</jats:p>

Characterisation of the DELLA subfamily in apple (Malus x domestica Borkh.)

“…These observations support a model in which DELLA proteins are central control points that integrate information from a number of signalling pathways and repress growth until conditions are optimal (Achard et al 2006;Alvey and Harberd 2005). In apple, the termination of vegetative growth and transition to floral commitment is a complex process that appears to be regulated by light intensity, temperature, vernalisation and non-autonomous rootstock effects (Hirst and Feree 1995;Johnson and Lakso 1985). Spur-type shoots terminate growth in early summer, whereas extension shoots continue leaf initiation and internode elongation for 4-8 weeks (Fulford 1965(Fulford , 1966.…”

Architecture and size relations: an essay on the apple (Malus × domestica, Rosaceae) tree

“…A second factor is the root system, which has been used as an efficient although empirical means to control tree size, with variable results on flowering (i.e., dependent on the genotype; Webster et al, 1985). The effects of the root system have been studied using various plant materials: own-rooted trees (usually micropropagated; Webster et al, 1985;Zimmerman and Miller, 1991;Quamme and Brownlee, 1993;Hirst and Ferree, 1995a) and/or trees grafted on rootstocks (Lockard and Schneider, 1981;Cummins and Aldwinckle, 1983;Lehman et al, 1990;Warrington et al, 1990;Barritt et al, 1995;Ferree et al, 1995;Hirst and Ferree, 1995a;Costes et al, 2001) or on various rootstock-interstock combinations (Seleznyova et al, 2003). The root system, from ''dwarf'' to ''vigorous,'' strongly influences overall tree size, with own-rooted trees generally equivalent to or larger than trees of the same genotype grafted on the most vigorous clonal rootstocks (Ferree, 1988;Larsen and Higgins, 1990;Quamme and Brownlee, 1993) or on seedling rootstocks (Zimmerman and Miller, 1991).…”

“…Trunk cross-sectional area (TCSA) and branch cross-sectional area (BCSA) are the main traits used to characterize the influence of the root system on tree growth (Westwood and Roberts, 1970;Moore, 1978). They are positively related to shoot length at trunk and branch levels (Hirst and Ferree, 1995a). A positive correlation probably exists between global growth of the root and shoot systems (Zimmerman and Miller, 1991;Fallahi et al, 2002).…”

“…A major difficulty with analyzing growth and flowering is their dynamic nature; the size of the morphological entities (internode, annual increment) decreases as the branch system increases in size and complexity with age. This decrease is positively and linearly related to the number of growing laterals for both trunk (Costes et al, 2001) and branch (Hirst and Ferree, 1995a;Seleznyova et al, 2003) with no influence of the root system and is referred to as aging (Wareing, 1970;Hackett, 1985). However, these relationships between axillary shoots and either length or number of nodes have been established between mean points, each one corresponding to a rootstock or rootstock-interstock combination.…”

A model simulating deposition of Venturia inaequalis ascospores on apple trees*

“…Measurement of LAI directly in the orchard is difficult, but LAI can be estimated starting from mathematical functions relating air temperature to leaf area development (Lasko & Johnson, 1990). The average leaf size can be measured for each cultivar, as it is quite constant for different training systems and shoot types (Hirst & Ferree, 1995). Finally, H1 and H2, that is the height above the ground that contains apple leaves, can be easily measured for each training system.…”