Molecular genetic variability, population structure and mating system in tropical forages

Melissa Garcia,Liana Jank,Lucimara Chiari,Tatiana T Souza-Chies,Sueli S Pagliarini,Guilherme Toledo-Silva,C T Karia ,L Jungmann ,Cacilda Borges Do Valle ,Francisco Humberto Dübbern De Souza ,F G Faleiro ,Priscila Maria Stolses Bergamo Francisco ,Maria Imaculada Zucchi ,R Godoy ,Fernanda Witt Cidade ,Marcelo Ayres Carvalho ,Miguel Dall’agnol ,Adna Cristina Barbosa De Sousa ,R M S Resende ,B B Z Vigna ,Anete Pereira De Souza

doi:10.17138/tgft(1)25-30

Abstract

Microsatellite (SSR) markers were developed for the following tropical forage species, using accessions available from the plant genetic resources (PGR) collections held by EMBRAPA (Brazilian Agricultural Research Corporation): Brachiaria brizantha, B. humidicola, Panicum maximum, Paspalum spp., Stylosanthes capitata, S. guianensis, S. macrocephala, Calopogonium mucunoides and Centrosema spp. The markers were used to analyze population structure and genetic diversity, evolution and origin of the genetic variability in the center of origin, mating systems and genetic resources in EMBRAPA’s germplasm bank. The results shed light on the amount of genetic variation within and between populations, revealed the need in some cases for further plant collection to adequately represent the species in PGR collections, allowed us to assemble core collections (subsets of the total collections) that should contain most of the available diversity and (in the case of the legumes) showed the need to avoid unwanted outcrossing when regenerating conserved material. The data will allow plant breeders to better select accessions for hybrid production, discriminate between genotypes and use marker-assisted selection in breeding programs. Our results will also underpin the construction of genetic maps, mapping of genes of agronomic interest and numerous other studies on genetic variability, population structure, gene flow and reproductive systems for the tropical forage species studied in this work.

Highlights

Grasses from the genera Brachiaria, Panicum and Paspalum and legumes from the genera Stylosanthes, Calopogonium and Centrosema are among the most widely sown tropical forage species
A grouping analysis using the neighbor-joining method was consistent with the STRUCTURE analysis, and a combination approach suggested that this germplasm collection exhibits limited genetic variability despite the presence of 3 distinct allelic pools
This study revealed that the collection of accessions from the P. maximum region of origin was a rich source of genetic variability

Summary

Introduction

Grasses from the genera Brachiaria, Panicum and Paspalum and legumes from the genera Stylosanthes, Calopogonium and Centrosema are among the most widely sown tropical forage species. Despite the importance of sown tropical forages for the Brazilian cattle industry and the extensive literature on genetic diversity of the species mentioned above, little information is available on the molecular genetic diversity to be found in the germplasm collections and on the mating systems of some of these species, hindering advances through plant breeding programs. We have used simple sequence repeats (SSR) to evaluate the genetic diversity and population structure of the Brazilian germplasm collections of all species cited above and to estimate mating systems for some of them.

Results

Conclusion