| Sweet osmanthus (Osmanthus fragrans) is a kind of noteworthy horticultural plant and enjoys a reputation of being one of the Top Ten Traditional Flowers in China. The cultivars in other species as well as in sweet osmanthus are classified systematically aiming at establishing a rational cultivar classification system. The main results are summarized as follows:A criteria and terminology for describing cultivars are revised based on a morphologic analysis of the variation and evolutionary trend. The cultivar taxa (culta) of Osmanthus are proposed as consisting of cultivar system (originated species), cultivar groups (if needed) and cultivars based on approaches of principles and ranks for cultivar classification. Ornamental cultivars in the genus Osmanthus derived from 5 different species, and could be categorized to 5 cultivar systems as O. fragrans, O. heterophyllus, O. fortunei, O. delavayi and O. cooperi cultivar system. In O. fragrans, 4 cultivar groups are recognized as Siji Group, Albus Group, Lute us Group and Aurantiacus Group.After a comparative study on morphology of 4 cultivar groups, a new thought is proposed that Siji Group is supposed to be hybrid originated and that the evolutionary tendency of flower colors is from white or yellowish white to yellow and to orange or orange-red. The evolutionary sequence of cultivar groups from primitive to evolutionary in O. fragrans is Siji Group, Albus Group, Luteus Group and Aurantiacus Group orderly. This opinion contrasts to traditional ideas. Two types of lamina are found in Siji Group cultivars. It has never been reported before. The scientific names of 4 cultivar groups are verified.Sweet osmanthus cultivars in China are comprehensively identified and revised with detailed description and verified scientific names. 157 cultivars are recognized, including 18 cultivars in Siji Group, 57 in Albus Group, 45 in Luteus Group and 37 in Aurantiacus Group; 44 cultivar names are reduced as synonyms; some incorrect identification is corrected; 46 cultivars are recorded and described as new. In addition, 12 cultivars in O. heterophyllus, 3 in O. delavayi, 4 in 0. X fortunei, and 2 in O. cooperi are recorded and some cultivar names in O. heterophyllus are verified and corrected.Pollen morphology of 12 species and 41 cultivars in 0. fragrans is examined with SEM. Pollen grains of the genus are tricolporate, N3P4C5 type according to Erdtman's NPC system, spheroidal, sub-spheroidal, or ellipsoidal in equatorial view, 3-lobed sub-spheroidal in polar view, with reticulate ornamentation. Principle component analysis shows that pollen size, shape, and ratio of colpus length to polar axis length are the main consideration in classification. Cluster analysis shows that pollen morphology is very important for species differentiations in Osmanthus, but not efficient for differentiations of cultivar groups. It also shows that O. fordii,O. X fortunei and O. cooperi are close to sweet osmanthus cultivars, which is in accordance with the results of orthodox taxonomy.Sweet osmanthus is an indigenous plant to China. Although it is difficult to discern the exact distribution area, it is certain that sweet osmanthus had distributed widely in the areas south of Yangtze River in ancient China, not just limited in Southwest China. Even now, there are still some survival wild communities of sweet osmanthus in Fujian, Zhejiang, Jiangxi and Hunan Province. Cultivars in 0. fragrans are originated in China, by ways of accumulating of minute variations, bud mutations, and hybridizations, etc. Many variations are existed in blossoming habits, flower colors, flower types, number of flower buds, pedicle length, flower scent, development status of pistil, flower diameter, branch gesture and lamina.The genus Osmanthus is of East Asia & North America Distributed Type, the species, however, can be divided into 3 types, namely North America, Tropical Asia and East Asia Distributed Types, and some subtypes based on their geographic distribution. East Asia Distributed Type, which accounts for 75.86% (22 speci... |
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