Evaluation of genome size and phylogenetic relationships of the Saccharum complex species

“ Saccharum complex” is a hypothetical group of species, which is supposed to be involved in the origin of modern sugarcane, and displays large genomes and complex chromosomal alterations. The utilization of restricted parents in breeding programs of modern cultivated sugarcane has resulted in a genetic blockage, which controlled its improvement because of the limited genetic diversity. The use of wild relatives is an effective way to broaden the genetic composition of cultivated sugarcane. Due to the infrequent characterization of genomes, the potential of wild relatives is diffused in improving the cultivated sugarcane. To characterize the genomes of the wild relatives, the genome size and phylogenetic relationships among eight species, including Saccharum spontaneum , Erianthus arundinaceus , E. fulvus , E. rockii , Narenga porphyrocoma , Miscanthus floridulus , Eulalia quadrinervis, and M. sinensis were evaluated based on flow cytometry, genome surveys, K-mer analysis, chloroplast genome sequencing, and whole-genome SNPs analysis. We observed highly heterozygous genomes of S. spontaneum , E. rockii , and E. arundinaceus and the highly repetitive genome of E. fulvus . The genomes of Eulalia quadrinervis , N. porphyrocoma , M. sinensis , and M. floridulus were highly complex. Phylogenetic results of the two approaches were dissimilar, however, both indicate E. fulvus displayed closer relationships to Miscanthus and Saccharum than other species of Saccharum complex. Eulalia quadrinervis was more closely related to M. floridulus than M. sinensis ; E. arundinaceus differ significantly from Miscanthus , Narenga, and Saccharum , but was relatively close to Erianthus. We proved the point of E. rockii and E. fulvus should not be classified as one genus, and E. fulvus should be classified as the Saccharum genus.