The effects of pollinizers, pollen and pistil quality, and fruit set of Japanese quince (Chaenomeles japonica) cultivars and perspective hybrids

Japanese quince (Chaenomeles japonica) produces a relatively small number of fruit almost every year despite many flowers blooming annually. This is probably due to pollination problems, as most genotypes are self-sterile. Therefore, pollinators play an important role in ensuring good Japanese quince yields. The aim of the study was to evaluate the quality of pollen and pistils of cultivars and promising hybrids, and to determine the degree of self-fertility and identify more suitable pollinators for Japanese quince cultivar ‘Rondo’. On average, pollen germination in vitro changed from 36.5 to 55.1% during the study. Defective pistils formed in 9.1-81.8% of all investigated cultivars, with numbers fluctuating depending on genotype. The largest number of defective pistils were found for cultivar ‘Darius’: 64.9%. A negative correlation was determined between the number of defective pistils and the final fruit set at open pollination. Artificial self-pollination was performed for 4 years. ‘Rasa’ was the only cultivar with a consistent fruit set (from 6.3 to 19.1%) every year. Due to meteorological conditions differing between years, ‘Rasa’ is now considered self-fertile, which is a valuable trait for C. japonica. The combinations of the 6 genotypes with ‘Rondo’ showed fruit set between 2.06 and 11.2% throughout the study period. ‘Rondo’ had the highest fruit set when pollinated by ‘Ada’ in both years (10.2 and 19.1%, respectively). Compared with open pollination (9.4 and 13.6%, respectively), a higher number of harvested fruits was obtained when ‘Ada’ was used as a pollinator.