The Studies On The Pollination And Fertilization Biology Of 'Josengwhangkeum' Pear

The biological characteristics of pollination and fertilization has a great effect on plants cultivation and breeding. Using'Josengwhangkeum',a new and excellent pear (Pyrus pyrifolia) cultivar as material, we investigated the anthesis, correlation between pollen and pollination and fertilization, pollination tree selection, pollination period and the whole process of fertilization by field observation, pollination experiments, paraffin sectioning and fluorescence microscope observations, The main results are as follows:1. Both Self-pollination of'Josengwhangkeum' and cross-combination 'Josengwhangkeum'x'Shinseiki' set no fruits, displaying strong self and cross incompatibility. In other cross-pollination combinations the inflorescence fruit set and per follower fruit set reached 74% to 100%,56% to 89%, respectively, which were significantly higher than those under natural pollination conditions. The best pollination variety for'Josengwhangkeum' was determined as'Huanghua', followed by 'Hosui'.2. There are 5650 pollen grains per anther in'Josengwhangkeum'.Of its pollination varieties, the number of pollen grains of 'Huanghua' is highest,9730 per anther, whereas the number in 'Niitaka' is lowest,656 per anther. The number in other pollination varieties varied from 5000 to 8160 per anther.3.'Josengwhangkeum'has strong pollen fertility with pollen viability of 77.2% and pollen germination rate of 56.6%, thus it can be used as a good pollination variety for other pear cultivars. Of the seven cultivars used as pollen acceptors in our cross experiments,'Niitaka' has lower pollen viability (20.4%) and lower pollen germination rate (15.0%). In contrast, other 6 cultivars have higher pollen viability and higher pollen germination rate, varying from 64.3% to 85.6%, and 50.2% to 70.2%, respectively. According to the germination rate of'Josengwhangkeum'in different period, the most appropriate time for pollen collection was in the first day before blooming and the blooming day.4. Investigation on active stigma and fruit set after pollination in different period revealed that the valid pollination period for'Josengwhangkeum'was in six days:two days before flowering till the 4th day after flowering; the most appropriate period was in four days:two days before flowering till the 2nd day after flowering.5.'Josengwhangkeum' has four ventricles in each anther; the anther wall development belongs to bi-cotyledon type; glandular tapetum; The meiosis in the microspore mother cells belongs to a simultaneous type and the microspores are arranged in a tetrahedron shape in the tetrads;pollen matures seven to nine days before blooming, ripened pollen 2-cell type. Gynoecium ovary has five carpels, five ventricles, and two ovules in each ventricle; four megaspores formed from megaspore cell meiosis range in a line, the one located the extensity is valid, and develops into eight mature nucleus megaspore during the blooming day by three mitoses, and megaspore growth belongs to Polygonum type. During growing process, the microspore occurrence along with male mate formation not only have a comparative stable homologous relation with macrospore occurrence and female mate formation, but also have relative steady connection with the shape and character of blooming bud and inflorescence. The inner development process can be speculated by observing the outer configuration of pistil and androecium.6. Both self ('Josengwhangkeum'×'Josengwhangkeum')and non-self ('Josengw-hangkeum'×'Huanghua') pollen could germinate on the stigma, but there were apparent differences between self and non-self pollination and fertilization process. Self pollen geminated on the surface of stigma in two hours after pollination, whereas pollen tube stopped growth at the 1/3 location away from stigma after eight hours and the tip of which expanded into sphericity, displaying self-incompatibility. In contrast, non-self pollen geminated in one hour after pollination, and the pollen tube elongated to the middle parts of style after eight hours, entered ovary after 24 hours, reached into embryo sac after 48 hours, and double fertilization was finally finished after 72 hours.