Floral Structure and Breeding Systems of Manglietia conifera Dandy (Magnoliaceae)

Abstract

Manglietia conifera Dandy is a fast-growing tree species that has been introduced to China from Vietnam, which has great potential for commercial planting. However, plantation development is hindered by a lack of seed material, due to low natural seed-set in locally grown trees. Thus, we investigated the morphological characteristics of male and female flower organs, and conducted controlled pollination to understand the breeding systems of the species. The individual flower of M. conifera is bisexual, and the stamen group is polymerized at the base of the receptacle. Pollen is symmetrically distributed on both sides. Controlled pollination suggests that apomixis does not occur in M. conifera. Results from the flower structure, pollen-ovule ratio, outcrossing index, and controlled pollination indicated that the breeding system in M. conifera was outcrossing (partially self-compatible, pollinators required), and self-incompatibility occurred in a later stage of embryonic development. Moreover, the self-incompatibility phenomenon was revealed by the abnormal germination of pollen on the stigma. This paper provides a basis for controlled pollination programs of M. conifera.Breeding systems play a decisive role in the success of reproduction in plants [10][11][12], and research in this field mainly includes floral characteristics, pollination and mating systems [13]. Flowering pattern and flower longevity directly affect the type of breeding systems [14,15]. Flower arrangement is also an important factor that influences mating success [16]. Understanding the floral structure is the basis for studying breeding systems [17][18][19]. Murawski [20] divided mating systems into selfing, mixed mating and outcrossing. Individuals with hermaphrodite flowers may resort to self-pollination, which leads to minimum genetic variation in their offspring [21]. However, geitonogamy may also mitigate pollen limitation in self-compatible plants [22]. In addition, morphological characteristics of the flower and breeding systems of a plant are useful to research in order to explore the causes of plant abortion. The breeding systems and abortion mechanism of plants are discussed by means of the hybridization index, pollen-ovule ratio, bagging test and other methods and indicators [23,24]. Therefore, floral syndrome and breeding system investigations are not only conducive to understanding the pollination mechanism and mating patterns, but also have scientific significance for further investigating the evolution and environmental compatibility of plants [25].Thus, we analyzed the floral structure, breeding system and controlled pollination of M. conifera: (1) What are the floral structure characteristics of M. conifera? (2) What are the breeding systems, results from flower structure, pollen-ovule ratio, outcrossing index, and controlled pollination? (3) What are the results of controlled pollination, and what are the barriers to successful pollination, and fruit and seed-set? The answers to these questions can contribute to artificial pol...