Characterization and taxonomical note about Thai Erianthus germplasm collection: the morphology, flowering phenology and biogeography among E. procerus and three types of E. arundinaceus

Erianthus, one of the genus in Saccharum complex, is important genetic resources for sugarcane improvement. The morphology and flowering phenology of 108 accessions belonging to Erianthus procerus and three types of E. arundinaceus collected from throughout Thailand were compared. PCA analysis based on 22 characteristics clearly supported the separation of Type II and Type III of E. arundinaceus from E. procerus and Type I of E. arundinaceus according to their morphological characteristics, particularly their bud size, and the development of root primordia, which greatly affected axis I of the PCA analysis. E. procerus and Type I showed overlapping in many of their characteristics including their flowering periods. Flower characteristics such as rachis joint length, which were used for previous taxonomic classifications, were not available for the classification of the Thai samples because of the wide variation and overlapping among them. Most of these phenotype similarities and differences are considered to have developed convergently as a result of niche adaptation. Type II and III inhabit riverbanks and streambeds where floods occur frequently, while E. procerus and Type I mainly grow in non-flooding areas such as mountainous grassland, the edge of forests, and beside fields. All Thai Erianthus show unique geographic distributions in Thailand. In particular, the biogeographic boundary between Type II and Type III appeared to be located at the Isthmus of Kra. Although some types showed morphological similarities, reproductive isolation among the four groups seemed to be maintained by differentiation in geographic distribution, habitat preference, and flowering timing.