Evaluation of Pollen Quality and Self-Fertility in Selected Cultivars of Asian and European Pears

Asian pears have become increasingly popular in the European market, but their cultivation history in Europe is rather short. Pear is a demanding species in terms of pollen - donor cultivar. The self-fertility phenomenon in Asian pear cultivars is not currently known. The study was conducted in a 6-year pear orchard (of 23 Asian and 5 European cultivars) at the Mendel University in Lednice (Czech Republic). The following traits were assessed: number of pollen grains, pollen viability, pollen grain germination, self-fertility and the pollen germination index (PGI). European cultivar - 'Clapp's Favourite' and Asian cultivars - 'Zao Su Li', and 'Shinko' were characterized by the highest number of pollen grains (over 50,000 grains). Asian cultivar 'Dangshansu Li' had the lowest number of pollen grains (less than 10,000 grains). The pollen viability of Asian pears ranged between 90 and 100%. Among European pears, 'Williams Bon Chretien' and 'Clapp's Favourite' exhibited the highest pollen viability (90%), while the lowest viability was observed for the pollen of cultivars 'Beurre Bosc' and 'Alexander Lucas' pear (60-70%). Additionally, it was found that the germination capacity of the latter two cultivars was very weak (40-70%). After open-pollination all investigated cultivars exhibited greater pollen germination index (PGI) comparing to selfpollination. After the cross-pollination the percentage of pollen tubes below the 20% value at half the length of the pistil suggested a strong incompatibility between the crossed cultivars. The results clearly showed that none of the Asian cultivars are self-fertile, and they require a pollen - donor to produce fruits.