PROGNOSTIC ESTIMATION OF STRAWBERRY VARIETIES FOR RESISTANCE (SUSCEPTIBILITY) TO STRAWBERRY SPIDER MITE
A methodological approach, based on the projection evaluation of strawberry varieties was presented in accordance to their basic biological traits, as well as to the reproduction index of strawberry spider mite, Tetranychus atlanticus, that can demonstrate resistance (susceptibility) to phytophagan. The study included 5 varieties of strawberries: Torpeda, Troitskaya, Tsaritsa, Swede and Elsanta. Quantitative biological responses associated with leaves (number of spring and summer leaves per plant, leaf surface area, specific leaf area) were calculated to characterize their resistance (susceptibility) during 2 following years, as well as phytophagan fecundity for 6 days under optimal laboratory conditions. Relative resistant (tolerance) varieties were accepted those which had larger number of leaves, larger leaf surface area, larger specific leaf area, and where less fecundity of a strawberry spider mite was realized. It was found that correlation coefficient (r) between traits «Number of spring leaves per plant» and «Fresh leaf biomass» was 0.865, between traits «Number of spring leaves per plant» and «Leaf surface area» - 0.838. Negative correlation coefficient was found between traits «Number of spring leaves per plant» and «Specific leaf area» (r = -0.730); it showed that if the variety had a small number of leaves, than leaves had larger specific leaf area, and vice versa. Comparison between traits «Fresh leaf biomass» and «Specific leaf area», where correlation coefficient (r) was -0.854, confirmed the correlation pattern. As metrological base of prognostic estimation of strawberry varieties for resistance (susceptibility) to strawberry spider mite were taken principles of optimization and optimal management, when the biological indexes were presented to establish of possible ranges of variables resistance and to get extreme trait values. Deviations from average value for each variety were calculated within tested index. Basing on principles of optimal management, the sum of deviations from the mean values was taken to calculate total index of the prognostic estimation of strawberry varieties on resistance (susceptibility) to strawberry spider mite was taken. The varieties of strawberry were ranged in accordance to the sum of deviations. Assuming equal exposure to each variety according to strawberry spider mite it was found that the most resistant (tolerance) variety was Torpeda, that had larger leaf surface area, obvious specific leaf area, and low fecundity of strawberry spider mite on the leaf (the total difference from mean value was +20.4%). The least resistant (tolerance) variety was Swede (the total difference from mean value was -14.5%). 1t would be advisable to find specific importance of each tested trait responsible for resistant to phytophagen under conducting the same investigation in future.