The effects of pollinizers on pollen tube growth and fruit set of European plum (Prunus domestica L.) in a Nordic climate

Abstract Norwegian plum production is characterized by climatic limitations, different flowering time, deficiently of wholly-adapted cultivars and appropriate pollen donors for cultivars that can be grown in this region. This study evaluated the progamic phase of fertilization and fruit set in four European plum cultivars (´Mallard´, ´Edda´, ´Jubileum´, and ´Reeves´) after crossing with different pollinizers over two years (2018/2019). Reproductive parameters, in vitro pollen germination, number of pollen tubes in the upper part of the style and locule of the ovary, number of pistils with ovule penetrated by pollen tube, fruit set in all crossing combinations, and fruit set in open pollination of pollen recipient cultivars showed different adaptability of both recipient and donor cultivars to the specific ecological conditions prevailing in Western Norway. The pollinizers ´Victoria´, ´Opal´ and ´C. Lepotica´ proved to be a very good pollinizers for cultivar ´Jubileum´, while pollinizers ´R. C. Souffriau´ and ´Valor´ for the cultivar ´Reeves´. Cultivars ´Opal´, ´R. E. Prolific´ and ´Mallard´ are excellent pollinizers for ´Edda´ in conditions of higher temperatures during flowering period and post-flowering period. Cultivar ´C. Lepotica´ proved to be the best pollinizer for ´Edda´ in conditions when the temperatures were lower. Cultivars ´Opal´ and ´R. E. Prolific´ can be considered as good pollinizers for ´Mallard´.