Study On Morphology And Molecular Phylogeny Of Melilotus Spp.

Melilotus is an important leguminous forage including annual and biennial types and comprises 19 species. Morphology and molecular phylogeny of 48 populations of 18 species in Melilotus genus were studied. M. alba and M. officinalis are 2 cultivated species and widely used for forage production. The genetic diversity of 91 populations within these 2 species was investigated.1. A total of 48 populations of 18 species of Melilotus were collected, and 5 seed morphological traits (seed length, seed width, seed width to length ratio, seed circumference, total weight of 100 seeds) and 9 agronomic traits (plant height, fresh matter yield and dry matter yield, stem to leaf ratio, chlorophyll content, leaf area, leaf color) were measured to compare the seed morphological and plant agronomy diversity among populations. The seed color was found to be yellow or gray and varied among species. The significant difference was found among species. Seed sizes ranged from 1.48 to 3.48 mm in length and 1.04 to 2.63 mm in width. The coefficients of variation (CV) of seed length and seed width were 89.30% and 86.00%, respectively, the CVs of the remaining traits were low. In addition to width-to-length ratio, seed length, seed width, seed circumference, total weight of 100 seeds showed a significant difference among populations (p< 0.05). Leaf color contains two types, light green and dark green. The chlorophyll content and leaf area were extremely significant difference among populations (p<0.01). Plant height, fresh matter yield and dry matter yield, photosynthetic rate also showed difference among populations (p<0.05). Among them the heaviest plants are the population of Ames18402 of M. spicatus which can reach 37.33g. Stem to leaf ratio showed no significant difference among populations.2. Three genes matK, rbcL and trnL-trnF of cpDNA and ITS of nrDNA were used to study the interspecific relationships among 48 populations of 18 species within Melilotus genus. The results showed that the Melilotus genus is clearly monophyletic in the legume family. The nrDNA ITS providing more informative characteristics (9.8%) than cpDNA (3.0%). Both Bayesian and maximum-parsimony approaches were used to analyze the data, the four trees showed that Melilotus genus has closely relationships with Medicago and Trifolum in Leguminous. Melilotus include two closely related groups, especially are clade I and clade II. M. spicatus, M. indicus and M. segetalis form a clade. M. infestus, M. siculus and M. sulcatus are closely related.3.91 populations including 44 M. alba populations and 47 M. officinalis populations were collected. The diversity of sequence, haplotypes, among (within) species, among (within) regions were studied by ITS gene and trnL-trnF gene. The results showed that the aligned length of trnL-trnF sequences were 459bp and ITS sequences were 714bp and there were 14 variable sites, 6 single site and 8 parsimonious informative sites. TrnL-trnF sequence comprising 7 haplotypes, among them 3 sites are indels. ITS sequence comprising 13 haplotypes and they are all substitution. The genetic diversity of M. officinalis was higher than M. alba in two squences through analyzing the diversity. Haplotypes of M. alba and M. officinalis in the phylogenetic tree showed that two species have gene flow and genetic resources communication.