Genome constructing opens new opportunities in apple (Malus domestica Borkh.) breeding for scab immunity, fruit quality and easy orcharding

Varieties which are immune to scab, triploid, with the fruits of high commercial quality, columnar, for growing in superintensive gardens, are a priority in apple ( Malus domestica Borkh.) breeding. In addition, the varieties must have a high adaptiveness and productivity in specific agro climatic conditions. Scab caused by Venturia inaequalis (Cke. Wint.) is one of the most harmful diseases of apple ( Malus domestica Borkh.) trees. This publication gives brief results of apple breeding for scab resistance. All-Russian Research Institute of Breeding Fruit Crops (RIBFC) is a pioneer in the development of scab immune home apple cultivars the development of which has been conducted since 1977. A list and origin of the best ten immune cultivars from twenty-two ones developed at the institute are given. The development of the digenic cultivars ( Vf + Vr, Vf + Vm ) with more prolonged and stable resistance to scab in contrast to monogenic cultivars is undertaken. Genetic and immunologic principles of breeding have been developed along with practice approaches. Methods of the artificial scab infection have been improved. Scientific recommendations on the intensification and acceleration of breeding have been worked out on a new genetic basis, i.e. with the donors having Vf gene. Another priority in breeding is the development of triploid apple cultivars, which are characterized by less year periodicity of fruit-bearing, higher fruit marketability and heightened autogamy. Using donors of diploid gametes, which have been cytoembryologically studied, for the first time in Russia and in the world a series of triploid cultivars have been developed at the RIBFC, nine of which are zoned (Avgusta, Bezhin Lug, Alexandr Boiko, Darena, Maslovskoe, Orlovskii Partizan, Osipovskoe, Patriot and Yablochnyi Spas). It has been found that 2×/4× and 4×/2× are the most promising crossing combinations for obtaining triploid seedlings. Breeding for columnar apple cultivars have been conducted at the RIBFC since 1984. Eight columnar apple cultivars developed at the RIBFC allow establishing super intensive orchards. Combining scab immunity ( Vf), triploidy (3×) and columnar habit ( Co ) in one genotype is difficult task. This problem can be solved by hybridization of columnar cultivars with Vf + 4× donor 30-47-88 (Liberty × 13-6-106) which has been obtained due to pre-breeding. A pattern of obtaining seedlings which combine scab immunity (Vf), columnar type ( Co) and triploid set of chromosomes, is given.