New insights into intergeneric relationships of Hickeliinae(Poaceae:Bambusoideae) revealed by complete plastid genomes

The Hickeliinae(Poaceae:Bambusoideae) is an ecologically and economically significant subtribe of tropical bamboos restricted to Madagascar,Comoros,Reunion Island,and a small part of continental Africa(Tanzania).Because these bamboos rarely flower,field identification is challenging,and inferring the evolutionary history of Hickeliinae from herbarium specimens is even more so.Molecular phylogenetic work is critical to understanding this group of bamboos.Here,comparative analysis of 22 newly sequenced plastid genomes showed that members of all genera of Hickeliinae share evolutionarily conserved plastome structures.We also determined that Hickeliinae plastome sequences are informative for phylogenetic reconstructions.Phylogenetic analysis showed that all genera of Hickeliinae are monophyletic,except for Nastus,which is paraphyletic and forms two distant clades.The type species of Nastus(Clade Ⅱ) is endemic to Reunion Island and is not closely related to other sampled species of Nastus endemic to Madagascar(Clade Ⅵ).Clade Ⅵ(Malagasy Nastus) is sister to the Sokinochloa+Hitchcockella clade(Clade Ⅴ),and both clades have a clumping habit with short-necked pachymorph rhizomes.The monotypic Decaryochloa is remarkable in having the longest floret in Bambuseae and forms a distinct Clade Ⅳ.Clade Ⅲ,which has the highest generic diversity,consists of Cathariostachys,Perrierbambus,Sirochloa,and Valiha,which are also morphologically diverse.This work provides significant resources for further genetic and phylogenomic studies of Hickeliinae,an understudied subtribe of bamboo.

The identity of Dinochloa species and enumeration of Melocalamus(Poaceae:Bambusoideae) in China

Three woody bamboo species collected in Hainan,China in 1940 have been described as Dinochloa based on vegetative specimens.However,the identity of these species has long been in doubt,largely because the vegetative phase in species of Dinochloa is morphologically similar to that in species of Melocalamus,a climbing or scrambling bamboo genus of the paleotropical woody bamboos(Poaceae:Bambusoideae)that consists of about 15 species and one variety.To determine the phylogenetic affinity of the three Dinochloa species from Hainan,we sampled almost all recognized Chinese species of Melocalamus and representative species of Dinochloa as well as other closely related genera,performed molecular phylogenetic analysis,and compared their morphology based on herbarium and fieldwork investigation.Our ddRAD data indicate that the three species from Hainan are closely related to Melocalamus,not Dinochloa.Morphological analysis showed that these three species have a climbing habit but do not grow spirally,their culm leaves have smooth bases,and there is a ring of powder and/or tomenta above and below the nodes.Taken together our findings indicate that the three species from Hainan originally published in Dinochloa should be transferred to Melocalamus,i.e.,Melocalamus orenudus(McClure) D.Z.Li& J.X.Liu,Melocalamus puberulus(McClure) D.Z.Li & J.X.Liu,and Melocalamus utilis(McClure) D.Z.Li &J.X.Liu,respectively.This study concludes with an enumeration of Chinese species of Melocalamus,with a key to nine recognized species and one variety,and a lectotypification for M. compatiflorus.

BambooBase:A comprehensive database of bamboo omics and systematics

Dear Editor,Bamboos(Bambusoideae,Poaceae)are of significant economic and ecological importance,supporting billions of people and contributing to international trade(Wu et al.,2023).They play a crucial role in carbon fixation and support a multitude of other species including the giant panda(Clark et al.,2015).Since the release of the first draft genome of moso bamboo(Phyllostachys edulis)(Peng et al.,2013),there has been a notable increase in the sequencing,assembly,and annotation of diverse bamboo genomes(Guo et al.,2019;Zheng et al.,2022;Ma et al.,2024).An existing resource for bamboo genomics,BambooGDB(Zhao et al.,2014),provides information based on the individual draft reference genome of moso bamboo.What is needed,however,is a resource reinforcing multiple genome assemblies in Bambusoideae to enable researchers to unravel the evolutionary history of chromosomes and genes through cladespecific comparative genomic investigations.Here,we present BambooBase(https://bamboo.genobank.org/),a newly developed web-based database designed to provide a seamless user experience for bamboo omics and systematics.

Genome Sequences Provide Insights into the Reticulate Origin and Unique Traits of Woody Bamboos

Polyploidization is a major driver of speciation and its importance to plant evolution has been well recognized.Bamboos comprise one diploid herbaceous and three polyploid woody lineages,and are members of the only major subfamily in grasses that diversified in forests,with the woody members having a tree-like lignified culm.In this study,we generated four draft genome assemblies of major bamboo lineages with three different ploidy levels(diploid,tetraploid,and hexaploid).We also constructed a high-density genetic linkage map for a hexaploid species of bamboo,and used a linkage-map-based strategy for genome assembly and identification of subgenomes in polyploids.Further phylogenomic analyses using a large dataset of syntenic genes with expected copies based on ploidy levels revealed that woody bamboos originated subsequent to the divergence of the herbaceous bamboo lineage,and experienced complex reticulate evolution through three independent allopolyploid events involving four extinct diploid ancestors.A shared but distinct subgenome was identified in all polyploid forms,and the progenitor of this subgenome could have been critical in ancient polyploidizations and the origin of woody bamboos.Important genetic clues to the unique flowering behavior and woody trait in bamboos were also found.Taken together,our study provides significant insights into ancient reticulate evolution at the subgenome level in the absence of extant donor species,and offers a potential model scenario for broad-scale study of angiosperm origination by allopolyploidization.