Karyotipic asymmetry of both wild and cultivated species of Pennisetum

Abstract

This study aimed the establishment of the relation between karyotipic asymmetry values obtained for different accessions of both wild and cultivated species of Pennisetum from Germplasm Bank of Embrapa Gado de Leite/Juiz de Fora-Minas Gerais State, Brazil. Conventional cell cycle synchronization protocols and Feulgen staining method were used to obtain metaphases plates. The wild-type accessions corresponded to the species P. setosum (2n=6x=54), P. nervosum (2n=4x=36), and P. orientale (2n=4x=36), and the cultivated to P. purpureum (2n=4x=28) and P. glaucum (2n=2x=14). No significant difference was found for the total length of chromosomes (p≥0.05) among the species. The analysis of intra-chromosomal asymmetry (A1) and inter-chromosomal asymmetry (A2) has shown that P. setosum has a tendency to chromosome asymmetry. P. nervosum, P. orientale, and P. purpureum have presented an intermediary level of asymmetry and P. glaucum, low asymmetry. Considering Stebbins criteria, the karyotype of P. glaucum and those from the three wild species fitted into the category 1A-symmetrical. With regard to P. purpureum, karyotypes of the accessions BAGs 54, 65 and 91 fitted into the category 2B and the other two genotypes (BAGs 63 and 75) fitted into the 1A. Comparison between the karyotype classification according to the inter-and intra-chromosomal asymmetry and Stebbins methodologies revealed that this last one alone was not able to detect small variations between karyotypes of the taxa closely related.Key words: Pennisetum purpureum, Pennisetum glaucum, germplasm, karyotype. RESUMO ASSIMETRIA CARIOTÍPICA DE ESPÉCIES SILVESTRES E CULTIVADAS DE PENNISETUMO objetivo deste estudo foi estabelecer a relação entre os valores de assimetria cariotípica obtidos para diferentes acessos de espécies silvestres e cultivadas de Pennisetum do Banco de Germoplasma da Embrapa Gado de Leite em Juiz de Fora (MG). Para obtenção das metáfases, utilizaram-se os protocolos convencionais de sincronização do ciclo celular e coloração pelo método de Feulgen. Os acessos silvestres correspondem às espécies P. setosum (2n=6x=54), P. nervosum (2n=4x=36) e P. orientale (2n=4x=36) e os cultivados a P. purpureum (2n=4x=28) e P. glaucum (2n=2x=14). Para o comprimento total dos cromossomos não foram observadas diferenças significativas (p≥0,05) entre as espécies. Pela análise da assimetria intra (A1) e intercromossômica (A2) observa-se que P. setosum tem maior tendência à assimetria. P. nervosum, P. orientale e P. purpureum tiveram grau intermediário de assimetria e P. glaucum, menor assimetria. Considerando os critérios de Stebbins, os cariótipos de P. glaucum e das três espécies silvestres analisadas enquadraram-se na categoria 1A-simétrico. Para P. purpureum, os cariótipos dos acessos BAGs 54, 65 e 91 enquadraram-se na categoria 2B e os outros dois genótipos (BAGs 63 e 75), na 1A. A comparação entre as classificações dos cariótipos obtidas conforme as metodologias de assimetria inter e intracromossômica e a de Stebbins revelou que esta última não perm...

Fitotoxicidade do chumbo na germinação e crescimento inicial de alface em função da anatomia radicular e ciclo celular.

“…e ácido acético glacial na proporção de 3:1) e armazenadas em freezer a -18ºC. As lâminas foram confeccionadas pelo método de esmagamento (TECHIO et al, 2010). Para tanto, os meristemas apicais foram hidrolisados com ácido…”

Karyotype diversity analysis and nuclear genome size estimation for Pennisetum Rich. (Poaceae) ornamental grasses reveal genetic relationship and chromosomal evolution

“…belonging to the Heterostachya section were closer to the members of the primary gene pool belonging to the Pennisetum section, according to their cross ability, than members of the other morphological sections. Techio et al (2010) also found that P. orientale and P. purpureum were limited to closer areas in a graphic of dispersions, indicating more karyotypic homogeneity between them and a better possibility of gene exchange. However, in the present study, members belonging to these two sections were clustered in two respective groups, either morphologically or cytologically.…”

“…The increase in karyotype asymmetry occurs due to the change of the centromere to terminal or sub-terminal positions and to differences in the relative size of the chromosomes of the complement, making the karyotype more heterogeneous (Stebbins, 1971;Techio et al, 2010). Moreover, diversity in chromosome asymmetry and size reflects chromosome re-patterning during evolution within the genus (Schubert, 2007), and these might have played an important role in the speciation of the Pennisetum genus.…”

“…Generally, species with more symmetric karyotypes, small genomes and a higher number of chromosomes are considered more primitive in a certain group of plants (Leitch et al, 2007;Peruzzi et al, 2009;Techio et al, 2010;Bennett and Leitch, 2011). For Pennisetum, the ancestral traits of the genus have been widely reported to belong to the group that presents a basic chromosomal number x = 9, small chromosomes, apomictic mode of reproduction and a perennial life cycle (Pantulu and Krishna, 1982;Martel et al, 2004;Chemisquy et al, 2010).…”

“…Among the nine Pennisetum taxa used as ornamental grass mentioned above, the chromosome characters of the following five taxa have been reported: P. orientale (Narayan, 1951;Chatterji and Timothy, 1969;Rangasamy, 1972;Vardhan and Lakshmi 1983;Techio et al, 2002Techio et al, , 2010, P. alopecuroides (Ono and Tateoka, 1953), P. villosum (Rangasamy, 1972), P. setaceum (Simpson and Bashaw, 1969), and P. glaucum × P. purpureum (Techio et al, 2002;Barbosa et al, 2003). These early studies, however, focused primarily on overall counts of chromosomes, rather than their individual morphology or genetic implications among species as revealed by karyotype parameters.…”