Morphological Type Identification of Self-Incompatibility in Dendrobium and Its Phylogenetic Evolution Pattern.

Shan-Ce Niu,Zhong-Jian Liu,Qing Xu,Hai-Jun Yang,Yun-Xia Niu,Yi-Bo Luo,Yong-Qiang Zhang,Guo-Qiang Zhang,Jie Huang,Pei-Xing Li,Li-Jun Chen

doi:10.3390/ijms19092595

Abstract

Self-incompatibility (SI) is a type of reproductive barrier within plant species and is one of the mechanisms for the formation and maintenance of the high diversity and adaptation of angiosperm species. Approximately 40% of flowering plants are SI species, while only 10% of orchid species are self-incompatible. Intriguingly, as one of the largest genera in Orchidaceae, 72% of Dendrobium species are self-incompatible, accounting for nearly half of the reported SI species in orchids, suggesting that SI contributes to the high diversity of orchid species. However, few studies investigating SI in Dendrobium have been published. This study aimed to address the following questions: (1) How many SI phenotypes are in Dendrobium, and what are they? (2) What is their distribution pattern in the Dendrobium phylogenetic tree? We investigated the flowering time, the capsule set rate, and the pollen tube growth from the representative species of Dendrobium after artificial pollination and analysed their distribution in the Asian Dendrobium clade phylogenetic tree. The number of SI phenotypes exceeded our expectations. The SI type of Dendrobium chrysanthum was the primary type in the Dendrobium SI species. We speculate that there are many different SI determinants in Dendrobium that have evolved recently and might be specific to Dendrobium or Orchidaceae. Overall, this work provides new insights and a comprehensive understanding of Dendrobium SI.

Highlights

The genus Dendrobium in the subfamily Epidendroideae, Orchidaceae, which consists of approximately 1450 species, is one of the largest genera in Orchidaceae
The cross-pollinated capsule set rate (CPCSR) for most species is higher than 50% and reaches nearly
Based onthe theresults results from artificial pollination andphylogenetic the phylogenetic of Dendrobium, we the species containing all types of and phylogenetic clades and observed pollen tube growth selected the species containing all types of CSR and phylogenetic clades and observed pollen tube using fluorescence microscopy after selfandselfcross-pollination over 2 years

Summary

Introduction

The genus Dendrobium in the subfamily Epidendroideae, Orchidaceae, which consists of approximately 1450 species, is one of the largest genera in Orchidaceae. Most of the species in this genus are epiphytes with high ornamental, medicinal, and commercial value and are favoured by botanists and plant enthusiasts [1]. As one of the largest Orchidaceae genera, most (72%) of the Dendrobium species that are known to be self-pollinated show self-sterility [2]. Half of orchid self-incompatibility (SI) species are from Dendrobium. SI, with multiple independent origins, exists in approximately 40% of flowering plants, based on the plant species tested [3,4]. SI is closely related to the formation and maintenance of the high diversity and adaptation of angiosperm species [5,6]

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