Evolutionary Patterns Analysis Of The Main Morphology And Karyotypic Ancestral Characteristics Of The Triticeae

Triticeae Dumortier is a group of plants in the Poaceae with about 450 species worldwide.This group contains important food crops such as barley(Hordeum vulgare L.),wheat(Triticum aestivum L.)and rye(Secale cereale L.),which are closely related to human life,as well as important forage grasses(e.g.,Agropyron cristatum(L.)Gaertn.,Psathyrostachys juncea(Fisch.)Nevski).It is a germplasm resource for the improvement of wheat crops and forage varieties.In addition,some species of Triticeae have the characteristics of drought resistance,cold resistance and salt resistance.They are the main components of natural grassland and artificial grassland(such as Aegilops tauschii L.,Elymus sibiricus L.,etc.),and play an important role in windbreak and sand fixation,soil and water conservation and ecological environment construction.Therefore,studying the phylogenetic relationship and evolution history of Triticeae plants will help to better understand the genetic relationship and genetic rules among Triticeae species,and provide a theoretical basis for the scientific and rational use of Triticeae genetic resources.In this study,60 Triticeae species representing 33 genome types(covering more than 70 %of the entire Triticeae genome)were sampled from 92 plants including 22 genera(covering more than 75 % of the entire genus classification level).Brachypodium distachyon was used as the outgroup.Based on the chloroplast genome sequence in the Genbank database,the following studies were completed:(1)Reconstruction of the maternal phylogenetic framework of Triticeae plants;(2)To evaluate the differentiation time and differentiation pattern of the main branches in the wheat pedigree framework;(3)Tracing the ancestral characteristics of genome size,karyotype and key phenotypic traits of Triticeae plants.The main results are as follows :(1)Phylogenetic analysis of the Triticeae shows that Psathyrostachys and Leymus constituted the basal group;Hordeum forms monophyletic;Agropyron,Kengyilia melanthera,Eremopyrum and Henradia are closely related;Aegilops,Amblyopyrum,Triticum,Secale,Crithopsis and Heteranthelium form the main Mediterranean distribution groups;Elymus,Campeiostachys,Kengyilia,Roegneria,Lophopyrum,Douglasdeweya,Anthosachne,Dasypyrum and Pseudoroegneria formed the main distribution groups in the Arctic temperate zone.(2)The estimated divergence time and geographical distribution characteristics of the Triticeae ancestors show that the origin of the ancestors of the Triticeae can be traced back to15.3 Mya,which originated in the Arctic-temperate region-Eurasia;the ancestral lineage of Leymus and Psathyrostachys diverged in the Arctic-temperate region-Eurasia at 3.64 Mya;the maternal ancestors of Hordeum diverged in the Arctic-temperate region-Eurasia at about4.22 Mya began to diverge;Agropyron,Eremopyrum and Henradia matrilines originated from a common ancestor in the Arctic-temperate region-Eurasia;Aegilops,Amblyopyrum,Triticum,Secale,Crithopsis and Heteranthelium matrilines Ancestor ca.6.96 Mya originated in the Mediterranean region;Elymus,Campeiostachys,Kengyilia,Roegneria,Lophopyrum,Thinopyrum,Douglasdeweya,Anthosachne,Dasypyrum and Pseudoroegneria maternal ancestors of ca.3.56 Mya originated in the Arctic-temperate region-Eurasia,with concomitant genealogical divergence to form Lophopyrum,Thinopyrum and Dasypyrum in the Mediterranean region.(3)The results of the ancestral genome size and karyotype variation of the Triticeae show that the ancestral genome size is about 7.31-8.74 Gb and there is a positive correlation between genome size and the ploidy of the species;The overall evolutionary trend of the karyotype evolves from symmetry to asymmetry.(4)The results of ancestral state reconstruction in the morphological characteristics of the Triticeae show that there is an evolution of perennial to annual,heterogamous to self-pollinated,rhizomeless to rhizomatous,spikelet number at rachis nodes from more to less,glumes and glume tips from absent to present,lemma marginal membranous from absent to present,lemma tepals from present to absent,palea ridges and ridge tepals from present to absent in Triticeae plants.The spikelet number,spikelet florets,plant height,spike length,spike width,glume length,glume width,lemma length,lemma awn length,distance from the base of the widest glume and glume awn length evolve in parallel in both directions;spike shape,lemma shape and glume shape tend to evolve from ovoid-lanceolate to elliptic;The shape of the palea apex evolves from pointed to rounded and flat.