博士（応用生命科学）

学位授与の日付

平成 1９年２月２０日

論「Studies on Diversity and Conservation of the Genus Begonia L.

文

名管開雲Kaiyun Guan

称号及び氏名(Begoniaceae) in China（中国におけるベゴニア属（シュウカイドウ科）の多様性と保全に関する研究）」
論文審査委員

主査 山口 裕文
副査 前中 久行
副査 森 源治郎

論文要旨
The understanding of the diversity and ecological nature of a plant group isfundamental necessity for conservation and sustainable use of plant and genetic
resources. The genus Begonia L. is among the ten most species-rich angiosperm
genera and has approximately 1,500 species comprising nearly all the species of thefamily Begoniaceae. It is considered as one of the most diversified genera inmorphological characters and habitats among the plant kingdom. The genus ismainly distributed in tropical and subtropical regions in Central and South America,Africa and Asia. Begonias are the famous ornamental plants.
China is one of the richest regions of Begonia species in the world. Studies on
Chinese begonias have been continuously carried out since 1940s. A detailed reviewof these studies revealed discrepancies and uncertainties in sectional and specificassignment. There were 255 Begonia species (legitimate taxa by 2006) described in
China. However, there is no clear systematic classification of them. It is, therefore,scientific and pragmatic merit to clearly delimit the species and systematic revisionof the Chinese Begonia.
Since previous researches on Chinese Begonia merely focused on systematicaltaxonomy, a comprehensive study on its biodiversity would be of great significanceto the effective conservation and sustainable utilization as genetic resources. The
present study aims to revise the known species, acquiring more basic scientific dataof specific, genetic and ecological diversities as well as the threatened status ofBegonia in China and accumulation of basic knowledge of horticulture.
Based on the published papers, herbarium specimens and field investigations aswell as observation on the live plants cultivated in the begonia house of Kunming
Botanical Garden, 210 taxa (including species, subspecies and varieties) wererecognized as real representatives of Begonia in China. The majority of Chinese

Begonia species are distributed in the provinces and regions south of theChangjiang River, especially in southwest China. The natural distribution ofBegonia in China ranges from 90 m to 3,400 m above sea level. Over 190 Begonia
species grow in the areas of 700-2,000 m in altitude. It was confirmed that themajority Chinese Begonia species are typical subtropical plants.
The Chinese Begonia has high morphological diversity in its growth habit, leaf,inflorescence, flower, fruits and seed. The leaf anatomy was studied on thirty
species in China. The leaf constitution characters were highly variable amonginter-section, unable to use for discrimination of sections. However, similarity of leaf
constitution was recognized between the species within the horticulturalclassification groups. The micro-morphological study on seeds of 68 species
indicated high interspecific diversity but unable to use at sectional level.
The chromosome numbers of 14 species were newly described. Cytologicalreview showed high diversity of Chinese Begonia in chromosome numbers. The
diverse chromosome numbers suggested that aneuploidy and polyploidization may
have played an important role on the speciation of Begonia.
The threatened status of Chinese Begonia was determined on the basis of IUCNRed List Categories and Criteria (Version 3.1). Among 210 Chinese Begonia taxa,
126 are critically endangered (CR), 45 endangered (EN), 28 vulnerable (VU), 4 nearthreatened (NT), 4 least concern (LC), 1 extinct (EX), and 2 data deficient (DD). The
results suggested that both external and internal factors cause to the threat ofendangered Begonia species in China. The main external cause is owing to thedecrease of natural forests and human activities. The internal cause is theextremely local distribution of Begonia. Around 60% of the Chinese Begonia species
are known only from single localities, and some of their populations are very small.
In an endangered species, B. parvula, pollination and reproductive nature weremonitored. B. parvula is insect pollinating and its four most frequent flower visitors
were Halictus sp., Luciola sericata, Amellia sp. and Nomia sp. The efficient visitors
discriminated female flowers. B. parvula could reproduce by particular bulbils,
which were produced from the vein of back surface of leaves. This phenomenon isunique to this species. That the flower visitors discriminated female flowers
explained the fact of not many fertile seeds and seedlings of this species in the wild.
The fertilization of female flowers of B. parvula is highly dependent on pollinatorvisits suggesting variation of pollination impacts on the reproduction.
The survival status of 277 introductions, including 146 species and/or taxa ofChinese Begonia, under cultivation was examined. Eighty-nine introduced species
could healthily or normally grow in Kunming, which occupied 61% of the total
introduced species. Fifty-five introduced species (ca. 38%) could survive in thebegonia houses, slightly damaged either by frost or heat, and the majority of themgrew again next year.
The Chinese Begonia species were classified into three horticultural groups on
the basis of their morphological characteristics and growing habits. Among 210 taxa
of Begonia in China, 131 species belong to rhizomatous type, 44 erect-stemmed type,and 35 tuberous begonias. Some Chinese Begonia species were suggested to have ahigh ornamental merit. And some are precious genetic resources for breeding
purpose. The species like B. asperifolia and other species growing in high altitude
will be valuable genetic resource for development of cold resistant cultivars. Thespecies like B. silletensis will be used for breeding of scented begonia cultivars.
The majority Chinese Begonia can be propagated by sexual or vegetative
propagation. However, some species were difficult to propagate. Tissue culture often species with high ornamental value or difficult naturally to propagate wasunsuccessful. Most begonias could grow well in humus or compost soil with pH
6.0-6.8. Suitable temperature is around 20oC for growing most begonias. Some
Chinese Begonia species were damaged by a temperature below zero, despite a hightemperature (above 34oC) didn’t cause serious damage. The hybridization
experiments showed high interspecific cross-compatibility. Twenty new begonia
cultivars were bred and registered through hybridization or selection of
spontaneous mutants including one scented cultivar.
Twenty-six Chinese Begonia species were used traditionally as medicine, food,beverage and pig feed. The antimicrobic activity of volatile emissions wasrecognized in 16 Chinese Begonia species to Staphyllococcus epidermidis,

Esherichia coli and Candida albicans, respectively. Begonias may be used for
medicinal and ecological phytodesign.
Two hundred and ten taxa of Begonia were recognized as real representatives inChina. The Chinese Begonia has high specific, genetic and ecological diversities.
Around 81% of the species are endangered. Both external and internal factors cause
to the threat of endangered Begonia species in China. The majority species can beprotected by ex situ conservation. Many species have ornamental merit or areimportant genetic resources. The results in this study are considered to be muchuseful for sustainable use of genetic resources and for effective conservation ofendangered species in the genus Begonia.

審査結果の要旨
ベゴニア属植物は 1500 種を含む世界の 10 大属のひとつで，形態および生態ともに多様性高く，観賞用をはじめとして有用かつ自然資源として重要な群である。中国はその多様性中心のひとつで，約 255 種が亜熱帯を中心に記録されている。このような植物の有効利用や遺伝資源の活用には，その多様性と生態を十分に把握する必要がある。
本研究では，中国の自生ベゴニアについて分類学的整理，形態的多様性および細胞遺伝学的特性の評価，稀少種としての現状把握，導入評価手法や保全手法にわたって網羅的に研究を行い，資源植物の多様性の保全と活用について考察している。
まず，ベゴニア属植物について資源植物学上のこれまでの情報と分類学的研究を整理した後， 中国に実存する種を 210 種（分類群）と査定し，それらの大多数が長江以南に分布し，標高 90m から 3400ｍにおよぶベゴニア属の垂直分布のうち 190 種が標高700m から 2000m の亜熱帯気候帯に生育分布することを指摘した。次に，形態的生態的多様性について考証し，生活型，葉形，花序，花器，果実，種子について外部形態，組織，表面構造がベゴニア属においては極めて多様で，種としてのまとまりはみられる
ものの従来の属内分類として提唱されていた節とは対応しないことを明らかにした。細

胞学的研究では 14 種の染色体数をあらたに明示するとともに，従来から調査していた中国産ベゴニア属植物の染色体変異と全世界の種の染色体数の変異パターンを分析し，大陸間で基本染色体数を異にする基本２倍体種から倍数化と異数性をともなった種分化によってベゴニア属の多様化がすすんだと考察している。
また，フィールド研究に基づいて中国に自生するベゴニアについて種ごとに稀少化・絶滅の程度を国際自然保護連合の国際基準に従って分析し，210 種のうち，126 種はレッドリストカテゴリーの絶滅危惧ⅠＡ類（CR）に，45 種は絶滅危惧ⅠＢ類（EN）に，
28 種は絶滅危惧Ⅱ類（ＶＮ）に，４種は準絶滅危惧（NT）に，さらに４種は LC にあたり，１種は絶滅（EX）し，２種は情報不足(DD)にあたるとし，ベゴニア属植物の稀少化や絶滅の原因には人間活動による影響の大きいことを指摘している。希少種のうち，B. parvula においては種生物学的解析を行い，送粉者の行動実態，花の性分化の生態学的意義，送粉者欠乏にともなう有性繁殖からの逃避など，希少種にみられる特性の進化を考証した。
さらに，中国産ベゴニアの 146 種について 277 回の昆明植物園への導入試験を行い，61％にあたる 89 種は導入可能で，55 種（38％）は通常の条件で維持できることを明らかにした。生育形については 130 種が園芸品種分類系における根茎型，44 種が直立茎型，35 種が球根型にあたると査定し，その特性は良くまとまった傾向を示し，この分類系による評価がベゴニアの園芸的利用のうえでは極めて有効であるとしている。中
国産ベゴニアの栽培方法についても分析し，育成に適切な土壌条件や温度条件を明らかにし，繁殖方法も分析している。また，いくつかの種については交雑実験を行い，種間交雑親和性の程度を明らかにするとともに，交雑による具体的な育種を試み，多数の新品種を育成し，ベゴニアにおける実際育種の基盤を構築した。
中国産ベゴニアは，観賞用として使われるだけでなく，多面的な有用性をもつことを，フィールド研究と耐菌性試験によって明らかにし，伝統的には様々な種が食用，薬用，醸造，飼料用に使われることと，その耐菌性の高い種においては室内デザイン植物としての意義を指摘した。
以上のように本論文は，これまで不明瞭であった中国のベゴニア属植物の分類，形態，生態，遺伝的特性，資源価値に関する実態を包括的に明らかにするとともに，多様性の保全と遺伝資源としての意義を考究している。本論文のモノグラフ的成果は，遺伝資源の保全と活用を含む資源植物多様性学および生態保全学における学術基盤を構築するだけでなく，育種学，植物分類学，景観植物学など，植物バイオサイエンスとその関連領域へ大きく貢献すると考えられる。したがって，学力確認試験の結果と併せて，申請者に博士（応用生命科学）の学位を授与することを適当と認める。