Genetic Diversity and Population Structure of Brachiaria Species and Breeding Populations

Abstract

Several apomictic Brachiaria (Trin.) Griseb. (syn. Urochloa P. Beauv.) species are commercially important tropical forage grasses, but little is known about the interspecific diversity and population structure within this genus. Previously published genus‐level Brachiaria phylogenies were conducted with few genotypes and contradicted well‐established morphological evidence and proven interspecific fertility in the B. brizantha (Hochst. ex A. Rich.) Stapf., B. decumbens Stapf., and B. ruziziensis (R. Germ. & C.M. Evrard) agamic complex. In this study, we characterized the genetic diversity and population structure of 261 genotypes from 14 Brachiaria species and a Panicum maximum Jacq. outgroup using 39 simple sequence repeat primers with 701 polymorphic bands. The genotypes included in the panel included germplasm accessions, commercial cultivars, and sexually reproducing breeding populations. Results of STRUCTURE, neighbor joining, unweighted pair group method with arithmetic mean, and multiple correspondence analyses confirmed the relatedness of the important commercial species B. brizantha, B. decumbens, and B. ruziziensis. Brachiaria decumbens was most closely related to B. ruziziensis, and the diploid sexual and tetraploid apomict B. decumbens accessions formed into two related but distinct groups. The close relationship between B. humidicola (Rendle) Schweick and B. dictyoneura (Figari. and De Not) Stapf. and the unique genetic makeup of the lone sexually reproducing B. humidicola accession were also corroborated by these results. Our findings largely supported morphology‐based taxonomic groupings in Brachiaria and indicated that genus‐level phylogenies are made more robust by the inclusion of many polymorphic markers and multiple genotypes from each species.

Genetic Diversity and Population Structure of Brachiaria (syn. Urochloa) Ecotypes from Uganda

“…The mean PIC values (0.89) deduced for markers in this study were comparable to studies of Silva et al for the top 30 most informative markers [21], Kuwi et al [30], and Pessoa-Filho et al [47] although it was higher than those reported in other studies [31,48,49]. Interestingly, the number of SSR alleles detected in this study (n = 584) was higher than those reported by Vigna et al [49], Jungmann et al [1], and Pessoa-Filho et al [47], but was lower than in the study of Trivino et al [50]. Differences in PIC values and SSR alleles among these studies could be attributed to several factors such as differences in number, genetic background, and genetic complexity of Brachiaria genotypes; variation in numbers and types of markers used in the analysis, and the difference among studies in allele scoring system and combinations thereof.…”

Genetic Mapping With Allele Dosage Information in Tetraploid Urochloa decumbens (Stapf) R. D. Webster Reveals Insights Into Spittlebug (Notozulia entreriana Berg) Resistance

“…Previous molecular studies have increased knowledge of U. decumbens genetics, including the development of sets of microsatellite markers (Ferreira et al, 2016; Souza et al, 2018) and the first transcriptome (Salgado et al, 2017) of the species as well as linkage maps from the interspecific progeny of U. decumbens × U. ruziziensis (Worthington et al, 2016). Other studies with molecular markers have analyzed the genetic relationships of this species to other species in the Urochloa genus (Almeida et al, 2011; Pessoa-Filho et al, 2017; Triviño et al, 2017).…”

Flow cytometry-based determination of ploidy from dried leaf specimens in genomically complex collections of the tropical forage grass Urochloa s. l

“…Urochloa tropical forage grasses and related genera studied here, including Andropogon, Pennisetum, Paspalum , and Panicum have a great potential for sustainable agriculture and intensive grazing management of cover crops. Some of them are included in the current breeding programs at CIAT and EMBRAPA, now mainly focused on crossing tetraploids within ‘ brizantha ’ and ‘ humidicola ’ agamic complexes and Urochloa maxima (Triviño et al ., 2017). These tropical forage grass group is genomically complex (Tomaszewska et al ., 2021), having species recognized as being very variable in number of chromosomes, and ploidy levels which is the result of apomictic reproduction, and reflecting the genetic diversity present in a given population (Jank et al ., 2011).…”

“…These tropical forage grass group is genomically complex (Tomaszewska et al ., 2021), having species recognized as being very variable in number of chromosomes, and ploidy levels which is the result of apomictic reproduction, and reflecting the genetic diversity present in a given population (Jank et al ., 2011). The ploidy levels of some Urochloa accessions have been previously measured (Penteado et al ., 2000; Jungmann, 2009; Jungmann et al ., 2010; Nitthaisong et al ., 2016; Triviño et al ., 2017), but some data vary between papers and reports (Tomaszewska et al ., 2021): thus values may requires checking for a particular accession name.…”