Effect of pollination mode on fruit set in blue honeysuckle (Lonicera caerulea L.)

Honeyberry’s popularity has been increasing because of its valuable traits: nutritional value of fruits (a high amount of ascorbic acid, potassium and polyphenolic compounds), early ripening (14 days before strawberry), exceptional hardiness and easy cultivation. However, there is still little known about the pollination biology of this species, which is essential for practical breeding purposes. In this study we evaluated pollen fertility in five cultivars and three breeding clones of this species. The impact of the manner of pollination on the fruit set and forming seeds has also been studied. The highest percentage of viable pollen was found in cultivars ‘Duet’ and ‘Wojtek’ (96%), whereas the pollen of ‘Chelyabinka’ cultivar had the lowest fertility (90%). The percentage of blue honeysuckle fruits obtained from open-pollinated flowers was high (on average 94.7%) compared to isolated flowers (on average 8.6%). The effect of cross-pollination with cv. ‘Duet’ indicates that the percentage of the fruit set, fruit weight and mass of produced seeds was higher when this cultivar was applied as maternal than paternal form. The number of seeds affected significantly the weight of the fruit in the case when cv. ’Duet’ was used as a paternal (correlation coefficient r = 0.45) or maternal form (r = 0.66), while for other methods of pollination this effect was insignificant. These results may be used to the most efficient establishment of plantations as well as for the realization of the breeding program of this valuable species.