The Systematic of Wild Banana Species (Musa L.) in Sulawesi: Morphology and Molecular Studies

Abstract

Information of wild banana species in Sulawesi was lack since there were no systematic study have been done before. Therefore, the systematic study of wild banana species (Musa L.) in Sulawesi was carried out. The study consist of (a) species delimitation of wild banana species (Musa L.) in Sulawesi to provide information of diversity and distribution of wild banana species in Sulawesi, and to provide species description and an identification key; (b) phylogenetic studies based on morphological characters and on internal transcribed spacer (ITS) regions of nrDNA sequences to determine the phylogenetic relationship between the species. A total of 110 specimen consisted of old and new collections deposited in BO and digital type specimen from MEL were examined morphologically. Phylogenetic tree used fifty three morphological characters was performed by Maximum Parsimony (MP) method using PAUP*4.0b10. While phylogenetic tree reconstruction based on ITS regions sequences used MP and Bayesian (MrBayes ver. 3.0) methods. Ensete and Musella were selected as the outgroup, whereas the ingroup represented by Musa species obtained from species delimitation study. Total DNA was extracted from silica-gel dried leaves by the modified CTAB method. ITS-5 and ITS-4 primers were used to amplify the ITS regions. Data of sequences were edited by using ChromasPro programme and were aligned by Muscle software. Species delimitation based on morphological characters showed 6 Musa and 1 incompletely known specimen housed in Sulawesi. There were 2 species (Musa acuminata var. tomentosa and M. celebica) considered as endemic to Sulawesi. The existence of M. balbisiana and M. itinerans are noted as new records. In Sulawesi, M. balbisiana represented by a specimen collected from Manado (North Sulawesi), while M. itinerans represented by specimens collected from Mt. Nokilalaki (Central Sulawesi), and Lore Lindu National Park (Central Sulawesi). Observation on the morphology of each species in this study enables the selection of important characters for species delimitation and identification. Position of suckers, petiole canal leaf, bract imbrications, bract behavior before falling, bract colour, fruit shape, and seed surface are important characters for delimiting and identifying taxa of wild banana species (Musa) in Sulawesi. Phylogenetic tree used morphological characters showed M. balbisiana and M. textilis placed in clade I in which they shared some similar characters for instance bract imbrication and behavior before falling. While Musa acuminata ssp. banksii, M. acuminata var. tomentosa, M. celebica, and M. itinerans were placed in clade II. The phylogenetic study based on morphological characters is incongruent with the phylogenenetic study based on ITS regions of nrDNA sequences. Phylogenetic tree used ITS regions of nrDNA sequences using MP and Bayesian methods showed M. textilis was placed in clade I and separated from M. balbisiana, M. itinerans, M. celebica, M. acuminata ssp. banksii, and M. acuminata var. tomentosa. Nevertheless, M. textilis and M. balbisiana have closed relationship. By using MP analysis, M. itinerans together with M. acuminata ssp. banksii, M. acuminata var. tomentosa and M. celebica were placed in the same clade, whereas Bayesian analysis showed M. itinerans was separated from M. acuminata ssp. banksii, M. acuminata var. tomentosa as well as M. celebica, and was placed in different clade. This study revealed that phylogenetic study of wild banana species (Musa) in Sulawesi based on morphological characters and ITS regions of nrDNA sequences support the monophyly of genus Musa and also support the taxonomic status of M. acuminata ssp. banksii as intraspecific taxa of M. acuminata. Moreover, analysis of ITS regions also showed that sequences of ITS regions of nrDNA could be used for phylogenetic tree reconstruction at the species level.