基于花粉微观特征的芒果属种质孢粉学研究及聚类分析

Palynological Study and Cluster Analysis of Mangifera Germplasm Based on Pollen Microscopic Characteristics

芒果属全球约有69个种,我国主要分布有8个种。我国悠久的芒果栽培历史形成许多具有地方特色的天然杂交种。在不断与环境协调发展的过程中,芒果枝叶、果实等外观形态发生了一定的变化,其花粉在保持遗传保守性和稳定性下却形成了独特的形态特征。为了深入研究芒果属植物花粉形态的分类学意义,理清芒果天然杂交种之间的系统发育关系,本研究基于花粉微观特征,对芒果属种质开展孢粉学研究及遗传关系分析。利用扫描电镜系统观察芒果属2个种32份芒果材料的花粉外部形态和花粉外壁纹饰等形态特征,在此基础上,对花粉6个数量性状进行聚类分析。结果表明:32份芒果种质花粉均属于N3P4C5型,极面观呈3裂三角形,赤面观呈近椭圆形,萌发沟孔为3条,萌发沟孔开裂度几乎到达花粉粒的两极;各材料的花粉形状大小、萌发脊宽窄、花粉纹饰、花粉外壁网孔密度和大小均存在差异;条纹状或网状纹饰和纹孔布满花粉粒表面,大多数芒果花粉属于网状纹饰,网孔形状多样,主要是圆形和长条形,纹脊粗糙,网孔分布密度在不同材料间存在差异。根据花粉粒大小、花粉形态、萌发脊宽、网孔大小和网孔密度等数量性状对参试材料进行聚类分析,32份芒果种质在相似距离为15时可分成三大类群,来自东南亚的马切苏、暹罗芒、仁和吕宋等芒果资源在谱系图中聚为一类,显示出一定的地域特征;萌发脊较窄的云南土芒、布鲁斯和象牙芒26号聚为一类;扁桃、收集的扁桃–芒与国内常见芒果栽培种聚为一类。原始的野生种白花本地芒与扁桃1号、扁桃2号、扁桃3号、扁桃4号聚为一组,该类资源具有原始型、野生型的特点。本研究可为芒果花粉形态的分类、亲缘关系和演化研究提供孢粉学依据。

There are about 69 species of Mangifera in the world,and 8 species are mainly distributed in China.The long history of mango cultivation in China has resulted in many natural hybrids with local characteristics.In the process of continuous coordinated development with the environment,the appearance of mango,such as branches,leaves and fruits,has changed to some extent,but its pollen has formed unique morphological characteristics while maintaining genetic conservatism and stability.In order to further study the taxonomic significance of the pollen morphology of mango plants and clarify the phylogenetic relationship between mango natural hybrids,this study carried out palynological research and genetic relationship analysis on mango germplasm based on the microscopic characteristics of pollen,and observed the pollen morphology and pollen exine ornamentation of 32 mango materials from two species of mango us-ing scanning electron microscopy.On this basis,cluster analysis was carried out on six quantitative characters of pollen.The results showed that the pollen of 32 the mango germplasms belonged to N3P4C5 type.The polar view was 3-split triangle,and the red view was nearly elliptical.There were three germination grooves,which almost reached both ends;There were differences in the shape and size of pollen,the width of germination ridge,pollen ornamentation,the density and size of pollen outer wall mesh among the materials.Stripes or reticular ornamentation and pits were all over the surface of pollen grains.Most mango pollen belongs to reticular ornamentation.Mesh shapes were diverse,mainly cir-cular and long,with rough ridges.Mesh distribution density varied among different materials.According to the cluster analysis of quantitative characters such as pollen grain size,pollen morphology,germination ridge width,mesh size and mesh density,the 32 mango germplasms could be divided into three groups when the similarity distance was 15.Mango resources from Southeast Asia,such as Machesu M.indica,Siam Mango M.indica,Ren He Carabao M.indica,were clustered into one group in the pedigree map,showing certain regional characteristics;Yun Nan Tu Mango M.indica,Bruce Mango M.indicaand Amemwins No.26 M.indica with narrow germination ridge were divided into one type;M.persiciformis,collected M.persiciformis and common domestic M.indica.cultivation species were grouped into one group.The original wild species,Bai Hua M.indica,was grouped with No.1 M.persiciformis,No.2 M.persiciformis,No.3 M.persiciformis,and No.4 M.persiciformis.The resource had the characteristics of primitive and wild types.This study would provide palynological basis for the classification,genetic relationship and evolution of mango pollen mor-phology.