Systematic Studies On Sporobolus

The Sporobolus is annual or perennial herbaceous which belongs to Poaceae. There are about 160 species, distributed in tropics, including 8 spices(one introduced) in China. The systematic position of Sporobolus has been disputed for a long time.In this study, the Poaceae division of data in experiments is based on �Flora of China�. For understanding the systematic position of Sporobolus, the morphological and molecular methods were conducted respectively. In morphology analysis, leaf epidermis and caryopsis morphology of Sporobolus and its related genera were scanned by light microscope and scanning electron microscope. In molecular study, the ITS sequence of nuclear genome and psbA-trnH sequence of chloroplast genome were used to build phylogenetic tree. The results were as follows:The epidermal morphology of leaves of 57 species of Sporobolus and 29 genera were analyzed by using light microscope and scanning electron microscope. According to the character of long cell, short cell, silica bodies, stomatal apparatus, papillae, prickle hairs and micro-hairs, the 57 species were divided into five types and four subtypes. Type I included the taxa of subfamily Pooideae. Type II represented subfamily Oryzoideae. Type III was consistent with subfamily Panicoideae. Type IV equaled to subfamily Eragrostoideae and Arundinoideae. Sporobolus and Crypsis belong to the same subtype. We suggested that Sporobolus should be assigned to tribe Sporoboleae of subfamily Eragrostoideae. Muhlenbergia should be assigned to tribe Muhlenbergiieae. The morphology of Spartina leaf epidermis was different from that of Sporobolus and Crypsis, which not belong to tribe Sporoboleae.Caryopsis morphology: Light microscope and scanning electron microscope were used to examine caryopsis features of 50 species which represent 28 genera. Based on the combination of the information of the size, colour, compressed mode, embryo ratio, stylopodium hilum and sculpturing patterns. Based on the comprehensive analysis of the character of caryopsis, the studied species was divided into three types and five subtypes, the results were consistent with the traditional classification. Type I was equal to subfamily Oryzoideae and Panicoideae. Type II corresponded to the subfamily Pooideae. Type III equivalent of subfamily Eragrostoideae and Arundinoideae. Sporobolus and crypsis belong to the same type, it should be attributed to tribe Sporoboleae of subfamily Eragrostoideae. The Muhlenbergia should belong to tribe Muhlenbergiieae.Finally, the ITS sequence and psbA- trnH chloroplast genome sequence were used to discover the systematic relation of Sporobolus. The maximum likelihood and bayesian method were used for Sporobolus and its related genera to construct molecular phylogenetic tree. Results showed that the Leersia group corresponded to the subfamily Oryzoideae. Poa, Alopecurus, Agrostis, Calamagrostis, Polypogon, Aniselytron and Phaenosperma were in the same clade of phylogenetic tree and respected the subfamily Pooideae. The clade which including Arundo and Phragmites was equal with subfamily Arundinoideae. Panicum and Arundinella got together, they equivalent of subfamily Panicoideae. The rest clade corresponded to the subfamily Eragrostoideae, including Sporobolus, Crypsis, Muhlenbergia, Cleistogenes, Eragrostis, Eleusine, Leptochloa, Dactyloctenium, Zoysia, Chloris, Cynodon, Spartina and Neyraudia. Sporobolus and Crypsis held together, corresponding to the tribe Sporoboleae. The trib Muhlenbergiieae as a sigle clade. The systematics position of Spartina needed to be verified further.