Regionally Adapted Model of an Ideal Malus×domestica Borkh Apple Variety for Industrial-Scale Cultivation in European Russia

Abstract

Apple is one of the most common fruit crops in the Russian fruit-growing industry, with huge varietal diversity and a vast cultivation area. The key regions for industrial-scale apple cultivation are the Central, Central Chernozem, and North Caucasian Districts. The main disadvantage of the relevant apple cultivars, especially the ones intended for intensified horticultural practices, is their low resistance against abiotic stresses and the fruit’s low quality and poor marketable condition. In Russia, apple is a crop of strategic importance that is consistently included in the household food basket, so fruit producers hold new varieties to higher standards and expect them to outperform their predecessors in terms of yield per plant, resistance against abiotic and biotic stresses, and quality, as well as show strong competitiveness and a more rapid return on investment, while satisfying stricter requirements. The objective of the present study was to summarize the data on the phenotypic manifestations of economically valuable traits of the apple cultivars approved for use in the Russian Federation depending on the region of cultivation; to determine the parametric characteristics of the most valuable traits in the form of a model of an “ideal” regionally adapted industrial cultivar, and to identify the sources of the traits in the regions suitable for their production. A regionally adapted model of commercial apple cultivars, characterized by 28 features and properties divided into three groups and defining the cultivar’s resistance against abiotic and biotic stresses, yield per plant, product quality, and suitability for mechanized harvesting, is presented in this paper. In the European part of Russia, the optimal parameters of a commercial apple tree cultivar are as follows: plant height on a medium-sized rootstock under 3 m; potential yield per plant of at least 25–50 kg; high fruit uniformity above 80%; winter and late-winter harvest maturity period; high storability of over 210 days and good transportability; average fruit mass from 120 g to 220 g; juicy and shattering crisp pulp; small seed cavity; fragrant fruits with taste rating of at least 4.5 points; appearance rating of 5 points and attractive, mostly red, glossy color with natural wax bloom; regular, symmetric, but diverse shapes; content of sugar above 10%, ascorbic acid above 15 mg/100 g, organic acids up to 1% (for dessert varieties); content of soluble dry solids of at least 20%. The cultivars that come closest to the regionally adapted model of an ideal variety based on the set of features discussed are as follows: Feya, Soyuz, Orfej, Margo, Sirius, Noktyurn, Vasilisa Karmen, Florina, Dayton, Early Mac, Gala and Gala Schniga in the North Caucasian District; Svezhest’, Orlovskoe Poles’e, Aprel’skoe, Ven’yaminovskoe, Bolotovskoe, Vympel, Uspenskoe, Fregat, Bylina, Flagman, and Akademik Kazakov in the North Caucasian District; and varieties Imrus, Mayak Zagor’ya, and Bolotovskoe in the Central District. These cultivars are characterized by high resistance against weather anomalies, scab immunity, high yields, marketable quality, and storability. In addition, in southern regions, a prolonged bloom period acts as a protective adaptive response to low-temperature stress.