MACROSCOPIC, MICROSCOPIC AND MOLECULAR EVALUATIONS FOR THE IDENTIFICATION OF ERYTHRINA SPECIES DISTRIBUTED IN THAILAND

Abstract

Plants in the genus Erythrina belong to the family FABACEAE. There are six species distributed in Thailand (Erythrina fusca Lour., Erythrina stricta Roxb., Erythrina crista-galli L., Erythrina subumbrans (Hassk) Merr., Erythrina variegata L., and Erythrina indica Lam.). Due to the similarity of the morphological characters and synonym in a vernacular name, the identification of these species is ambiguous. Therefore, an accurate investigation of their identities is essential. This research aimed to distinguish six Erythrina spp. through the macroscopic, microscopic, and molecular genetic analyses. The anatomical characteristics of each species (cross section of midrib) and the constant values of leaves including stomatal number, epidermal cell number, stomatal index, epidermal cell area, vein islet number and palisade ratio were investigated. The macroscopic characters and anatomical characteristics of the midrib of six investigated Erythrina species were illustrated. The stomatal type of all six species was paracytic type which was consistent with unique characteristics of plants in this family. In terms of microscopic leaf constant numbers, the stomatal number and stomatal indices in lower epidermis among these six species were overlapping, whereas the stomata in the upper epidermis were found only in E. crista-galli, E. subumbrans and E. variegata (60-136, 12-44 and 4-28 stoma/mm2 respectively). E. crista-galli demonstrated the highest number of upper stomata which could be used as an indicator for the identification. In addition, E. subumbrans and E. variegata exhibited distinct upper epidermal cell number (1080-1820 and 404-532 cell/mm2 respectively). This study revealed the overlapping of the palisade ratio among six Erythrina species. Nevertheless, vein islet number could be used to identify E. subumbrans from other species (12.75-20.75 and 3.50-11.00 cell/mm2 respectively). Moreover, the cross sections of the midrib of six investigated Erythrina species revealed the distinguished arrangement of tissue especially the vascular bundle. None of the trichome was found in these species. Additionally, the nucleotide sequences of five regions; ITS, matK, psbA_trnH, rpoC and ycf1 gene, were evaluated and compared among these species and 2 outgroups. The sequence lengths of gene among six Erythrina species were 650, 790, 375, 416 and 634 base pairs in length, respectively. The genetic relationship was demonstrated as phylogenetic tree constructed from each gene region. All studied of Erythrina were classified into 6 groups. E. stricta and E. subumbrans were close related these other species. In conclusion, leaf macroscopic and microscopic characteristics of six Erythrina species distributed in Thailand, both qualitative and quantitative, could be used as a tool for these plants authentication. Molecular genetic characteristics using ITS, matK, psbA_trnH, rpoC and ycf1 gene sequences provided valuable information to evidently support the identification of six Erythrina species.