Location: Plant Genetic Resources Unit (PGRU)Title: Evaluating and improving rootstocks for apple cultivation
Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: 5/15/2017
Publication Date: 7/6/2017
Citation: Fazio, G. 2017. Evaluating and improving rootstocks for apple cultivation. In: Evans, K., editor. Achieving sustainable cultivation of apples. Burleigh Dodds Science Publishing Limited. p. 135-153.
Technical Abstract: The foundations of a productive and healthy orchard are the rootstocks that provide anchorage, water and nutrients essential to the above ground portions of the trees. The utilization of composite trees has increased the efficiency of breeding productive apple trees by dividing the selection of scion traits and rootstock traits into two genetically (and functionally) different specimens which are then brought together through grafting. The central component of high-density systems is the rootstock, the part of the tree which provides size control to allow for high-density plantings. As part of the tree, the rootstock influences many factors in addition to tree size, particularly productivity, fruit quality, pest resistance, stress tolerance, and ultimately profitability. Breeding and evaluation of new apple rootstocks can be a very lengthy process; there are two ways to accelerate the process: the application of marker assisted breeding in the pipeline and/or the intensification of later stages of field testing. The first aims to eliminate substandard germplasm (non-precocious, non-dwarfing, susceptible to diseases, etc.) from the parental and progeny pools via the development and application of robust diagnostic markers. The second is to increase the number of clonal plants tested for each elite genotype and subject them to multiple phenotyping tests and environments that represent production regions. Tree-fruit growers must look to alternative, economically and environmentally sustainable management schemes of production to remain competitive in the international fruit market. They are doing this by establishing high-density plantings with much smaller trees using new cultivars. These high-density plantings may cost 10 to 20 times more to establish than low-density plantings, thus greatly enhancing the economic risk. Potential returns of high-density plantings, however, far exceed those of low-density plantings, particularly during the first 10 years after planting, often returning the grower's initial investment much sooner than the initially less-costly, low-density plantings. This book chapter describes traits aimed for improvement of sustainable apple cultivation and the evaluation efforts that transfer new rootstock technologies to apple growers worldwide.