The assessment of the variety and rootstock genotypes interaction in apple ( Malus domestica Borkh.) grafted trees using biometric methods

In grafted fruit plants with vegetative propagation the scion (variety) and rootstock influence each other in newly-formed variety-rootstock combination. Under intensive technologies of fruit production based on maximal realization of grafted fruit plants’ bio potential it is very important to obtain accurate knowledge about quantitative traits which characterize productivity and biometrical parameters of fruit plants. To forecast the productivity of apple ( Malus domestica Borkh.) trees, we studied the possibility of math modeling for the prediction of variety and rootstock influence on formation of quantitative traits in grafted plants using formulas offered by biometric genetics to estimate the same indexes in parent forms and their F 1 hybrids. The data of apple trees productivity obtained in Prikubanskaya zone of Krasnodar region in 1983 to 2003 years (a total of 22 years) were analyzed. We studied the variety-rootstock combinations (VRC) of four apple varieties (Idared, Golden Delicious, Jonathan, Korah) as scions and seven rootstocks (I-48-1, I-47-55, I-48-46, M2, M3, M4, M7) with regard to yields, the width of the crown from North to South and from West to East, the tree height and trunk diameter. An impact of the year conditions, the genotypes of the variety and the rootstock and their interaction on the yield of the variety-rootstock combinations was proven using math statistics. It was shown that the conditions of the year have the greatest effect (37 % of the total variance). Strength of the variety influence on the VRC yield was determined to be expressed with a several years interval. The rate of the rootstock impact and the cumulative effect of the scion and the rootstock were found to be roughly equial. For the first time for biological objects, which are characterized by non-linear relationship of traits, it is revealed that the forecasting models of VRC productivity based on multiple linear regression analysis with a linearized model is more effective and promising approach which takes into account the inadequacy of linear models previously considered. The histogram of residuals showed their normal distribution that is in conformity with correct use of the applied regression analysis. It provides a basis for adequate non-linear (quadratic) model of the yield production in each variety-rootstock combination as related to morphological and anatomical characteristics of grafted trees. Thus, based on theoretical analysis and the 22 year survey, we suggested the mathematical models for the variety and rootstock genotypes influence on quantitative traits in a grafted plant, primarily its productivity. It has been developed for the first time. This model enables more accurate control of stable and effective yield production in perennial crops.