Genomic behavior of hybrid combinations between elephant grass and pearl millet

Abstract

-The objective of this work was to evaluate the genomic behavior of hybrid combinations between elephant grass (Pennisetum purpureum) and pearl millet (P. glaucum). Tetraploid (AAA'B) and pentaploid (AA'A'BB) chromosome races resulting from the backcross of the hexaploid hybrid to its parents elephant grass (A'A'BB) and pearl millet (AA) were analyzed as to chromosome number and DNA content. Genotypes of elephant grass, millet, and triploid and hexaploid induced hybrids were compared. Pentaploid and tetraploid genomic combinations showed high level of mixoploidy, in discordance with the expected somatic chromosome set. The pentaploid chromosome number ranged from 20 to 34, and the tetraploid chromosome number from 16 to 28. Chromosome number variation was higher in pentaploid genomic combinations than in tetraploid, and mixoploidy was observed among hexaploids. Genomic combinations 4x and 5x are mixoploid, and the variation of chromosome number within chromosomal race 5x is greater than in 4x.Index terms: Pennisetum glaucum, Pennisetum purpureum, DNA content, interspecific hybrids, mixoploidy. Comportamento genômico de combinações híbridas entre capim-elefante e milhetoResumo -O objetivo deste trabalho foi avaliar o comportamento genômico de combinações híbridas resultantes do cruzamento entre capim-elefante (Pennisetum purpureum) e milheto (P. glaucum). Raças cromossômicas tetraploides (AAA'B) e pentaploides (AA'A'BB), resultantes do retrocruzamento do híbrido hexaploide com seus parentais capim-elefante (A'A'BB) e milheto (AA), foram avaliadas quanto ao número cromossômico e ao conteúdo de DNA. Foram comparados os genótipos de capim-elefante, milheto e de híbridos triploides e hexaploides induzidos. As combinações genômicas pentaploides e tetraploides mostraram elevado grau de mixoploidia, em desacordo com o complemento cromossômico somático esperado. O número cromossômico dos pentaploides variou de 20 a 34, e o dos tetraploides de 16 a 28. A variação do número cromossômico foi maior nas combinações genômicas pentaploides do que nas tetraploides, e a mixoploidia foi verificada entre hexaploides. As combinações genômicas 4x e 5x são mixoploides, e a variação do número de cromossomos na raça cromossômica 5x é maior do que na 4x.Termos para indexação: Pennisetum glaucum, Pennisetum purpureum, conteúdo de DNA, híbridos interespecíficos, mixoploidia.

Genetic diversity of elephant grass (Cenchrus purpureus [Schumach.] Morrone) for energetic production based on quantitative and multi-category traits

“…Similar results were found by Leão et al (2011), who evaluated the genetic diversity of 136 accessions of grape by quantitative morpho-agronomic traits and obtained 30 groups, with the largest concentrating only 30.14% of the accessions, indicating genetic variability and good division of the accessions among groups. Other studies have demonstrated that the number of groups formed is not always a synonym of high variability, because there may be a great accumulation of genotypes in a single group (Campos et al, 2010;Silva et al, 2013).…”

“…These results indicate variability in the germplasm bank, since although 40% of genotypes are gathered in only one group, 10 groups were formed. Similar results were obtained by Leão et al (2011), who evaluated 136 accessions of grape by multi-category descriptors and obtained nine groups formed, with good dispersion of the genotypes in each group, given that the group with the most accessions had 35.3% of the total 136, indicating great variability. Silva et al (2013), however, obtained 12 groups, evaluating 88 accessions of coffee, but also reported low variability, with 54.5% of the accessions in only one group.…”

“…Silva et al (2013), Neitzke et al (2010), and Leão et al (2011) also found a different number of groups and differentiated distribution of the accessions into the groups when comparing the cluster formed by quantitative and multi-category traits with 88 accessions of Coffea ssp., 17 accessions of pepper, and 136 accessions of grape, respectively. For that reason, Coimbra et al (2010) stated that these pieces of information on similarity should be used together.…”

“…Other studies have demonstrated that the number of groups formed is not always a synonym of high variability, because there may be a great accumulation of genotypes in a single group (Campos et al, 2010;Silva et al, 2013). In interbreeding (crossing), one expects to obtain maximal heterotic effect on the segregating generations, so it should be performed with parents belonging to different dissimilarity groups (Leão et al, 2011).…”

KARYOTYPE ALTERATIONS AFTER HYBRIDIZATION BETWEEN Pennisetum purpureum AND Pennisetum glaucum

“…The reunion of two genomes in a single nucleus results in intergenomic conflicts, leading to genetic and epigenetic reorganizations (Riddle;Birchler, 2003). This has been evidenced in works carried out with natural and synthetic hybrids, which have demonstrated that the new genomic constitution, resulting from hybridization, leads to elimination of DNA sequences (Feldman et al, 1997;Shaked et al, 2001;Leitch;Bennett, 2004;Leão et al, 2011;Nunes et al, 2013), chromosome rearrangements (Pires et al, 2004;Pontes et al, 2004;Udall;Quijada;Osborn, 2005), chromosome elimination (Germand et al, 2005;Ishii et al, 2010;Sanei et al, 2011;Andrade-Vieira et al, 2013), epigenetic alterations such as methylation of coding and non-coding DNA sequences Feldman, 2004;Salmon;Ainouche;Wendel, 2005;Lukens et al, 2006), gene silencing (Lee;Chen, 2001;Doyle et al, 2008;Gaeta et al, 2007;) and activation of genes and retroelements that alter the expression of adjacent genes (Adams;Wendel, 2005;Feldman;Levy, 2002Levy, , 2003.…”