Classification of Chinese Wintersweet (Chimonanthus praecox) Cultivars Supported by Pollen Morphology

To classify the Chinese wintersweet (Chimonanthus praecox) cultivars and to study their evolution based on pollen morphology. Pollens of 12 representative wintersweet cultivars were examined by scanning electron microscopy (SEM). Q-cluster analysis was carried out based on the observation results. Results are as follows: (1) The pollen grains were 2- lobed circular in polar view, elliptic in equatorial view. The pollen shapes were spheroidal or super-spheroidal by P/E (polar axis length/equatorial axis length) criteria. (2) According to pollen exine ornamentation, it was indicated that white wintersweet is most original. Yellow floral group could be classified into three subgroups: purple-hearted, halo-hearted and yellow-hearted type. Their evolutionary relationship was purple-hearted→halo-hearted→yellow-hearted. (3) Different wintersweet cultivars showed a different exine sculpture. Palynological analysis could be used in the classification of wintersweet cultivars. The result of cluster analysis indicated that the cultivars could be classified into three groups with a similarity coefficient of 0.41. Each group had similar pollen exine sculpture. It was found that the palynological classification coincided well with morphological classification. Our results support the suggestion that purple streaks or patches of inner-petals should be served as the first-order criteria in wintersweet classification.