Definition of Eight Mulberry Species in the Genus Morus by Internal Transcribed Spacer-Based Phylogeny

Abstract

Mulberry, belonging to the order Rosales, family Moraceae, and genus Morus, has received attention because of both its economic and medicinal value, as well as for its important ecological function. The genus Morus has a worldwide distribution, however, its taxonomy remains complex and disputed. Many studies have attempted to classify Morus species, resulting in varied numbers of designated Morus spp. To address this issue, we used information from internal transcribed spacer (ITS) genetic sequences to study the taxonomy of all the members of generally accepted genus Morus. We found that intraspecific 5.8S rRNA sequences were identical but that interspecific 5.8S sequences were diverse. M. alba and M. notabilis showed the shortest (215 bp) and the longest (233 bp) ITS1 sequence length, respectively. With the completion of the mulberry genome, we could identify single nucleotide polymorphisms within the ITS locus in the M. notabilis genome. From reconstruction of a phylogenetic tree based on the complete ITS data, we propose that the Morus genus should be classified into eight species, including M. alba, M. nigra, M. notabilis, M. serrata, M. celtidifolia, M. insignis, M. rubra, and M. mesozygia. Furthermore, the classification of the ITS sequences of known interspecific hybrid clones into both paternal and maternal clades indicated that ITS variation was sufficient to distinguish interspecific hybrids in the genus Morus.

Peer Review #2 of "Molecular phylogeny of mulberries reconstructed from ITS and two cpDNA sequences (v0.1)"

“…An alignment of the ITS sequences of the mulberry accessions is shown in Figure 1. We detected the 13-bp InDel reported previously (Zeng et al 2015). Further, we found three types of 13-bp sequences among the 33 mulberry accessions (CGTATACAATGCG, TGTGTGCAATGCG, and CGTACACAATGCG).…”

“…Morus yunnanensis was obtained from the Institute of Sericulture and Apiculture, Yunnan Academy of Agricultural Sciences, Mengzi, Yunnan province, China. The other mulberry accessions were obtained from the Mulberry Germplasm Nursery at Southwest University, China (He et al 2013;Zeng et al 2015), where they are preserved by propagation through grafting. The relatively closely related species Artocarpus heterophyllus was selected as the outgroup for the phylogenetic analyses based on ITS sequence (KT002551) and cpDNA sequences (MG434693).…”

“…atropurpurea (KU355276.1)) using VISTA viewer (http://genome.lbl.gov/vista/index.shtml) (Frazer et al 2004), we selected the two variable cpDNA sequences, trnL-trnF and trnT-trnL, for analyses. The ITS and the trnL-trnF sequences were amplified using primers described elsewhere (Taberlet et al 1991;Zeng et al 2015). We PeerJ reviewing PDF | (2019:06:38248:2:0:NEW 19 Oct 2019)…”

“…Manuscript to be reviewed Phylogenetic analyses of ITS sequences and cpDNA sequences were conducted using maximumlikelihood (M-L) and Bayesian inference (BI) methods. The first phylogenetic analysis was conducted using the ITS sequences of the 33 mulberry accessions determined in this study and those from another nine species (M. mesozygia HM747171 (Zeng et al 2015). The best-fit model SYM+G for BI analyses of ITS sequences was selected by the lowest AIC (Akaike Information Criterion) scores in MrModelTest 2.3 (Klaus-J et al 2004).…”

“…We wittiorum (clade B), and M. australis (clade B) in the phylogenetic analyses, as they represented six of the eight clades classified in a previous study (Zeng et al 2015). We constructed M-L and BI trees.…”