To the experimental confirmation of the hypothesis about an eco-genetic nature of the phenomenon genotype x environment interaction for woody plants

The hypothesis of the eco-genetic nature of the phenomenon genotype _ environment interaction (GEI) was developed by Russian scientists in 1984 after discovering an epigenetic phenomenon, the change in the spectra of genes that determine the same quantitative trait in annual crops with a change in the limiting factor. Perennial fruit trees are ideal objects for studying mechanisms of genotype _ environment interaction. Genetic diversity within a fruit tree variety is practically zero as the trees are genetically homogeneous clones due to grafting, plants in a commercial garden are of the same age because of simultaneous planting, and they have the same soil area of nutrition, that is, there is no superposition of genetic and environmental competition. Annual growth in thickness of trunk and branches is very informative, and the pattern of a tree's annual growth rings records information about growth conditions, above all weather conditions, for many years. We studied apple ( Malus domestica Вorkh.) and apricot ( Prunus armeniaca L.) varieties of northern and southern origin which possess different tolerance to weather stressors. To reveal alterations in the spectra of genes determining an increase in the thickness of a tree trunk and branches, we compared annual rings in the commercially grown trees of different adaptiveness which undergone the action of various limiting weather factors changing over a long period, particularly the effects of dry and hot years in contrast to the wet and cool years. It was revealed that wet and cold weather caused a bigger increase in branch thickness in the northern-originated apple variety Krasa Severa from Ekaterinburg with better genetic and physiological systems for cold resistance, whereas dry and hot weather similarly affected the southern-originated variety Bahorn from Uzbekistan. Pubescence of leaves and cuticle thickness which contribute to drought resistance can not contribute to an increase in cold resistance. Hence, a change in the incremental thickness grades suggests a change in the set of component traits, and, therefore, the sets of genes that determine these traits, with a change in the limiting factors of the environment. Thus, due to the choice of the varieties of different origin and adaptability and the years with contrasting limiting environmental factors, we succeeded to discover the facts that were predicted by the hypothesis of the nature of the genotype _ environment interaction phenomenon.