Abstract
Dimocarpus longan, commonly known as the longan, belongs to the family Sapindaceae, and is one of the most economically important fruits commonly cultivated in several regions in Asia. There are various cultivars of longan throughout the Thai-Malay peninsula region, but until now no phylogenetic analysis has been undertaken to determine the genetic relatedness of these cultivars. To address this issue, 6 loci, namely ITS2, matK, rbcL, trnH-psbA, trnL-I and trnL-trnF were amplified and sequenced from 40 individuals consisting of 26 longan cultivars 2 types of lychee and 8 herbarium samples. The sequencing results were used to construct a phylogenetic tree using the neighbor-joining (NJ), maximum likelihood (ML) and Bayesian inference (BI) criteria. The tree showed cryptic groups of D. longan from the Thailand-Malaysia region (Dimocarpus longan spp.). This is the first report of the genetic relationship of Dimocarpus based on multi-locus molecular markers and morphological characteristics. Multiple sequence alignments, phylogenetic trees and species delimitation support that Dimocarpus longan spp. longan var. obtusus and Dimocarpus longan spp. malesianus var. malesianus should be placed into a higher order and are two additional species in the genus Dimocarpus. Therefore these two species require nomenclatural changes as Dimocarpus malesianus and Dimocarpus obtusus, respectively.
Highlights
From Dimocarpus longan[5, 6, 10]
We aimed to investigate the evolutionary relationship of the genus Dimocarpus including longan cultivars (Dimocarpuslongan spp. longan) commonly grown in Thailand and determine the validity of species boundaries in Dimocarpus by combining multi-gene molecular phylogeny and morphological approaches
The sizes of PCR products amplified from ITS2, matK, rbcL, trnH-psbA, trnL-I and trnL-trnF
Summary
From Dimocarpus longan[5, 6, 10]. Of these, only Dimocarpus longan has its own variety. Given the agricultural and medicinal significance of longan, a number of studies have tried to develop molecular markers to assess the diversity of the numerous longan cultivars grown locally in China, Indonesia and Thailand as well as in germplasm collections from various regions. Such markers could potentially assist breeding program and facilitate authentication strategies such as, Random Amplified Polymorphic DNA (RAPD)[19], Amplification Fragment Length Polymorphism (AFLP)[20], Inter-Simple Sequence Repeat (ISSR)[21] and Single Nucleotide Polymorphism (SNP)[17]. We aimed to investigate the evolutionary relationship of the genus Dimocarpus including longan cultivars (Dimocarpuslongan spp. longan) commonly grown in Thailand and determine the validity of species boundaries in Dimocarpus by combining multi-gene molecular phylogeny and morphological approaches. These results should be of high interest to academics concerned about the future genetic conservation of Dimocarpus in the Thai-Malay peninsula region
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