Success Rate of Individual Pollinizers for the Pear Cultivars "Ingeborg" and "Celina" in a Nordic Climate

Abstract

Norwegian pear production is low due to climatic limitations, a lack of well-adapted cultivars and suitable pollinizers. However, nowadays it is increasing as a result of newly introduced and bred pear cultivars. Since cross pollination is necessary for high yields and good fruit quality, the aim of this investigation was to find the most suitable pollinizers for the pear cultivars "Ingeborg" ("Conference" x "Bonne Louise") and "Celina" ("Coloree de Juillet" x "Williams"). Self-pollination of "Ingeborg" and "Celina", together with "Conference", "Belle Lucrative", "Anna", "Clara Frijs", "Herzogin Elsa", "Kristina" and "Fritjof" as potential pollinizers, were studied in this experiment during the 2017 and 2018 seasons in Norway. The success rate of each pollinizer was tested under field conditions, while the monitoring of pollen tube growth was done using the fluorescence microscopy method. All reproductive parameters (pollen germination, number of pollen tubes in the upper part of the style, pollen tube number in the locule of the ovary, number of fertilized ovules, initial fruit set, and final fruit set) in all crossing combinations were higher in 2018 due to much warmer weather. Based on the flowering overlap and success rate of each individual pollinizer and fruit set, the cultivars "Anna" and "Clara Frijs" can be suggested as pollinizers for the cultivar "Ingeborg", while "Fritjof", "Anna", "Kristina" and "Herzogin Elsa" for the cultivar "Celina". An even distribution of two compatible pollinizers having overlapping flowering times with the main commercial pear cultivar is a general recommendation for commercial pear production.