ISHS Acta Horticulturae 293: IX International Symposium on Apricot Culture
APRICOT ROOTSTOCKS: PERSPECTIVE, UTILIZATION AND OUTLOOK |
| Author: | R.C. Rom |
| Abstract:
The apricot of commerce, Prunus armeniaca, spread over time as the result of social and economic exchange or military ventures from its zone of origin in Northeast China to Northwest China, Asia, Iran, Armenia, Syria and eventually, before the birth of Christ into Europe (Crossa-Raynaud and Audergon, 1987). This spread, however, has always been severely restricted to specific locations by the narrow limits of the apricot's ecological adaptation (Bailey and Hough, 1975). The apricot's introduction as a commercial crop to North America, South America and Oceania is more recent. Ecological adaptation is found in regions with a continental climate with about 500 mm rain per year and temperatures that do not fluctuate widely in winter, yet are sufficiently warm during the growing season (Bailey and Hough, 1975; Paunovic, 1977). Where local adaptation occurred whether through natural selection of escapes to the wild or included man's continued quest for superior types, through a selection process, a wide separation and disparity of genotypes and phenotypes among the socially or geographically isolated regions resulted. Four broad eco-geographic groups eventually evolved, each with a specific eco-adaptation (Kostina, 1969). Within each is a unique gene pool resource of biological properties that may be used by breeders for cultivar development. This same gene pool, which has been used for centuries as seedling rootstocks, now appears to be a source of rootstock problems as well as promise: problems when specific adaptive characteristics are ignored or are no longer an asset, and a promise when its specific gene resources are utilized. As commercial apricot production expands to meet market demands, it is moving from the scattered and somewhat isolated geographic regions to other temperate zone areas, frequently at lower altitudes, with different and often stressful soils and climates. Three climate zones are suggested as areas for expanded production, yet each zone has unique ecological characteristics that vary among the zones, and even within a zone there may be microclimate oases. Thus site selection remains important (Paunovic, 1988). An apricot cultivar's market acceptance is dictated by use, quality, and harvest season. However, yield is primarily controlled by the scion, yet more importantly, by the rootstock's endurance to biotic and environmental stresses. Just as a cultivar from one ecologic group may have adaptation limitations when moved to another environment, rootstocks may manifest similar adaptation problems and production limitations. Therefore, specific attention is now directed to apricot rootstocks from the view of perspective, utilization and outlook. | |
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