Studies On The Systematics Of Triarrhena Nakai (Gramineae)

Triarrhena is a small-sized gunus of Gramineae with only two species, which occurs in eastern Asia, particularly in China, but its taxonomic treatment has been a controversial matter. It was treated as an independent gunus, or a species under Miscauthus or Imperata. Triarrhena and its related species were studied by using integral methods involving leaf morphology and anatomy, cytotaxonomy, ITS sequences and ISSR analysis. The main points are as follows:1. Morphology and AnatomyLeaf morphological and anatomical characters in 5 varieties, 8 species of Triarrhena and its related genera were investigated under both light microscope (LM) and scanning electron microscope (SEM). Stomatal apparatuses were found on both upper and lower epidermis. Stomatal subsidiary cell, dome-shaped to triangular. Intercostal long cells, rectangular, slightly or markedly elongated between the veins. The walls of long cells between veins are rather straight, or sinuolate and sinuous. Silica-bodies, mostly dumb-bell shaped, occasionally double dumb-bell shaped, nodular and cross-shaped. Micro-hairs common in all species, prickle-hairs present in all species exept Imperata. Hook-hairs are only found in T. lutarioriparia var. humilior. Macro-hairs are found in Saccharum arundinaceum, I. cylindrical and Triarrhena lutarioriparia var. shachai. The number, shape and distribution of papillae in epidermal cells existed to some extent regular patterns in the taxa. Papillae widely spread in Triarrhena and I. koenigii. S. arundinaceum are not found on both epidermis. M. sinensis only on abaxial, not adaxial, epidermis, I.cylindrica on adaxial, not abaxial, epidermis. Only 4 rod like papillae on the individual stomata of Imperata. All the species belong to the panicoid type in terms of their leaf transverse sections, but the various taxa differ. Miscanth with single bundle-sheaths, others with double bundle-sheaths. Both leaf morphological and anatomical features possess important value for classification of Triarrhena and its related genera. 2. CytotaxonomyThe karyotypes of 4 varieties and 7 species in Triarrhena and its related species were reported. The chromosome numbers and karyotype formulae are as follows: M. sinensis , 2n = 38 = 28m+10sm ; M. floridulus, 2n=38=24m+14sm; T. sacchariflora, 2 n=38=22 m+16 sm ; T. lutarioriparia, Hanshou population 2 n=38=26 m+10sm+2st ,Nanchang population2 n=38=24 m (2SAT) +14 sm (2SAT) ; T. lutarioriparia var. levationodis, 2 n=38=30 m(2SAT) +8sm, T. lutarioriparia var. humilior , 2 n=76=52 m+20 sm+4 st, T. lutarioripariavar.planiodis, Anqing population 2 n = 38=22 m+14 sm (2SAT) +2st, Guichi population 2n= 38=26 m+12 sm, Jiujiang population 2 n=38=30 m (2SAT) +6 sm+2 st, Pengzepopulation 2 n=38=26m+10 sm+2 st; I. koenigii, 2n=2x=20=9m+lsm; S. arundinaceum,2 n=40; S. spontaneum, Nanchang population 2 n=64, Shicheng population 2n =70. All the karyotypes belong to 2B except I. koenigii with 1B type. The chromosome numbers of diploid and its karyotype of T. sacchariflora and the karyotypes of M. sinensis, M. floridulus, T. lutarioriparia var. lutarioriparia, T. lutarioriparia var. humilior , T. lutarioriparia var. planiodis and I. koenigii reported for the first time. The results of karyotype analysis indicate that Triarrhena closely related with Miscanthus Imperata. It is unreasonable to separate T. lutarioriparia and T. sacchariflora from Miscanthus to establish a new genus Triarrhena. We supported the point that T. lutarioriparia is a new species in Miscanthus, with its new name Miscanthus lutarioriparius.3. ISSR analysisEleven species in Triarrhena and its related genera were analyzed, by using ISSR genetic markers. One hundred primers were screened, 11 selected primers produced clear polymorphic patterns. 18～26 polymorphic bands could be amplified from each primer, with an average of 20.91 bands. The average genetic identity value of species was 0.714 ranging from 0.551 to 0.878. The ISSR marker data were analyzed using Nei's genetic distance. A dendrogram was constructed by using UPGMA method. Cluster analysis showed that all materials could be distinguished by ISSR markers. The different species in a genus were clustered together respectively, and had genetic variation in molecular levels. Distinct genetic differences exist among the species; The results are in agreement with the views of that Triarrhena has a very close relationship with Miscanthus. It is a supplemented method for analysis of the genetic variation in Triarrhena and its related species. ISSR was also used to investigate 50 accessions of five varieties of T. lutarioriparia from Jangxi, Hunan, Hubei and Anhui Province. Results showed that T. lutarioriparia possessed abundant and complicated genetic diversity.4. ITS sequences analysisThis study is to assess the phylogeny of Triarrhena and its related genera in Saccharinae (Gramineae) based on internal transcribed spacer (ITS) and the 5.8 s coding region of the nuclear ribosomal DNA. Neighbor-joining (NJ), maximum parsimony (MP), and maximum likelihood (ML) methods were employed to analyze the data sets with Phragmites australis as outgroup. The phylogenetic trees based on the data set show that the genus Miscauthus (including Triarrhena) formed a monophyletic group. Imperata cylindrica and Saccharum arundinaceum were sister group and formed a subclade, indicating their close affinity. The present authors suggest that Triarrhena should be merged with Miscanthus. The results of phylogenetic analysis also indicate that Saccharum arundinaceum has a closed relationship with Imperata, followed by Narenga and Miscauthus. However it is the most distant to the other species of Saccharum. Since the genera of Saccharum, Narenga and Erianthus are shown to be polyphyletic, further studies on their phylogenetic relationships are still needed.