Location: Plant Genetic Resources Unit (PGRU)Title: Chapter 2 - Advances in development and utilization of rootstocks for fruit tree cultivation
|ROBINSON, TERENCE - Cornell University - New York|
Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: 4/30/2019
Publication Date: 12/12/2019
Citation: Fazio, G., Robinson, T. 2020. Chapter 2 - Advances in development and utilization of rootstocks for fruit tree cultivation. Book Chapter. 1. http://dx.doi.org/10.19103/AS.2018.0040.02.
Technical Abstract: All commercial temperate zone fruit trees are composed of an aerial ‘scion’ cultivar grafted or budded on another cultivar which serves as the support root system referred to as the ‘rootstock’. The practice of budding or grafting desirable scion cultivars on rootstocks has been practiced for centuries due to the highly heterozygous nature of tree fruits (Tukey, 1978), most of which do not reproduce “true to type” by seed. Thus, in general, the seed from a desirable fruit variety will not result in a tree which produces the same fruit characteristics as the parent. To overcome this problem, fruit growers learned many centuries ago that a desirable genotype could be propagated asexually by budding (a single bud) or grafting (a small section of shoot with several buds) onto other plants with roots (usually the same or a closely-related species) and then allowing only the bud of the desirable cultivar to grow and develop into each tree's canopy, thus creating multiple trees of the desirable cultivar (Cummins, 1973; Larsen, 1976). For example, all of the 'Red Delicious' apple (Malus domestica) trees in the world originated from a single tree discovered in Peru, Iowa, in the 1800s. Thereafter, buds from the original tree were budded onto other apple seedlings, and later interspecific hybrid clones, that serve as rootstocks to produce the millions of 'Delicious' trees that have been grown around the world from until the present day. Similarly, 'Montmorency' sour cherry (Prunus cerasus) is a 400+ year-old cultivar that originated in France, but comprises the majority of sour cherry production in the United States, where it is grown primarily on Prunus mahaleb seedling rootstocks. The general history of all major fruit cultivars, including subtropicals like Citrus as well as temperate-zone fruit and nut trees, is similarly based on the propagation of superior fruiting genotypes on different rootstock genotypes. Not only does this provide a way to reliably reproduce the superior traits of the scion, but also a way to adapt its production to different localized soils, climates, and production systems. Historically, seedlings were used as rootstocks for deciduous fruit tree species such as apple, pear (Pyrus communis), peach (Prunus persica), tart and sweet (Prunus avium) cherry, apricot (Prunus armeniaca) and plum (Prunus domestica and Prunus salicina) (Sax, 1949). The classic way to produce a rootstock is to plant seeds and when the young seedling is 30-50 cm tall, bud or graft onto that seedling the desirable scion cultivar. However, with the exception of some peach and almond rootstocks, since each seedling rootstock is a unique genotype, there can be considerable variability in its own growth characteristics as well as the characteristics it may impart to the scion due to the heterozygosity of each fruit species, resulting in variability in tree performance in the orchard. Potential variations in seedling rootstocks include vegetative vigor, tree shape and size, yield, precocity of fruit bearing, fruit size, and susceptibility to root diseases and abiotic stresses. Nevertheless, almost all commercial orchards used seedling rootstocks until the 20th century. While this chapter focuses mostly on apple, it exemplifies the various inherent rootstock properties and rootstock-induced qualities on grafted scions that can be found in other temperate fruit rootstocks.