Genetic Diversity and Structure of Ruzigrass Germplasm Collected in Africa and Brazil

Abstract

ABSTRACTRuzigrass [Urochloa ruziziensis (R. Germain & Evrard) Crins, syn. Brachiaria ruziziensis Germain & Evrard] is a tropical forage native to Africa, first introduced in Brazil in the 1960s. Ruzigrass is diploid, presents sexual reproduction, and is a model species for the generation of genomic resources in the Brachiaria genus. Brachiaria species are the most important livestock forage in the tropics, covering more than 70 million ha in Brazil alone. We have used multiplex panels of microsatellite markers to characterize the genetic diversity of ruzigrass germplasm collected in Africa, and of a local population collected in Brazil, to obtain information for its conservation and use in breeding programs. Fifteen SSR markers were used to Genotype 114 ruzigrass samples. Summary statistics, as well as estimates of FST and partitioning of genetic diversity were obtained. Clustering and genetic structure analyses were performed. Results showed high values of heterozygosity in the African and Brazilian populations. Although African and Brazilian samples formed distinct groups in clustering analyses, and Bayesian analysis of genetic structure distributed samples into three clusters, estimates of pairwise FST values showed no differentiation between African and Brazilian groups of samples. Results indicated that the introduction of ruzigrass in Brazil did not cause a major decrease in genetic diversity. Brazilian local populations might harbor favorable alleles that will be useful for ongoing and future breeding programs. They offer great opportunities for ruzigrass germplasm collection and conservation of genetic diversity, before attempts to access germplasm in its center of diversity are undertaken.