APS_April 2023

J ournal of the A merican P omological S ociety

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Figure 6. Ripe fruit from Michurin’s cultivars: A) ‘Rubinovaya’ (PI 635902), B) ‘Burka’ (PI 635903), C)‘Granatnaya’ (PI 699312) Photo credit: Ryan King, USDA, 5 August, 2021. Figure 6. Ripe fruit fromMichurin’s cultivars: A) ‘Rubinovaya’ (PI 635902), B) ‘Burka’ (PI 635903), C)‘Granatnaya’ (PI 699312) Photo redit: Ryan King, USDA, 5 August, 2021.

oped many cultivars in each of these gen era. Michurin was able to facilitate crosses among species and genera that were unable to naturally cross through sexual hybridiza tion. One of the methods that he developed for overcoming these barriers is “vegetative rapprochement,” in which he grafted spe cies or genera to each other and then crossed to the scion years after the successful graft union was formed (Sokolov, 2015). Michurin wrote “this operation is much more likely to succeed in such cases, because by the time the crossing is performed the plants have de veloped a mutual affinity in their vital func tions” (Michurin, 1949). Using vegetative rapprochement, Michurin was able to cross “apple with pear, Amygdalus [almond] with plum, Amygdalus with peach, apricot with plum, bird cherry with sour cherry, moun-

tain ash with pear, apple with hawthorn, and quince with pear.” He suggests that by using this technique, “an infinite prospect opens here for the possibility of obtaining entirely new species of fruit plants with unprecedent ed forms and properties” (Michurin, 1949). Michurin noted the wide array of po tential quality traits available in Sorbus . “Fruit breeders both here in our Union and abroad have paid absolutely no attention to the improvement of mountain ash variet ies” (Michurin, 1949). He made numerous improvements in Sorbus and released sev eral cultivars. In a recent study, Michurin’s hybrids were noted to have large, dark fruits with lower astringency and exceptionally high levels of antioxidants and polypheno lics, compared to other S. aucuparia, which is likely due to having Aronia in their pedi-