Cytogenetics of Pennisetum purpureum Schumack x Pennisetum glaucum L. hybrids and their parents

Abstract

Cytogenetic studies were carried out on five accesses of interspecific hybrids of Pennisetum purpureum and Pennisetum glaucum and their parentals, which are part of the Forage Germplasm Bank of the Centro Nacional de Pesquisa de Gado de Leite of EMBRAPA, Brazil. The mitotic cytogenetic analysis, performed using stain by Schiff reactive, confirmed the chromosome number of 2n = 14, 28 and 21 for the accesses of P. glaucum, P. purpureum and their hybrids, respectively. For each access, descriptions of the chromosome complement and idiograms are presented which allowed to establish the karyotypic relationships between the hybrids and their parentals. Based on the total chromosomal length data it was possible to establish the karyotype classification of the accesses concerning symmetry. While the karyotype of P. glaucum accesses was considered symmetric, hybrids presented asymmetric karyotypes. For P. purpureum, two accesses (BAGs 63 and 75) showed symmetric karyotype and three (BAGs 54, 65 and 91) were asymmetric. For the interspecific hybrids it was possible to infer the origin of some parental chromosomes based on the total chromosomal length measurements, satellite presence and chromosome morphology. INDEX TERMS:Elephant grass, pearl millet, interspecific hybrids, cytogenetic, ideograms, chromosome. CITOGENÉTICA DE HÍBRIDOS ENTRE Pennisetum purpureumSchumack E Pennisetum glaucum L. E SEUS GENITORES RESUMO Foram realizados estudos citogenéticos em quinze acessos do Banco de Germoplasma Forrageiro, da Embrapa Gado de Leite, sendo cinco híbri-dos interespecíficos de Pennisetum purpureum e Pennisetum glaucum e seus genitores. As análises citogenéticas mitóticas realizadas mediante coloração com reativo de Schiff confirmaram o número cromossômico de 2n =14, 28 e 21 para os acessos de P. glaucum, P. purpureum e híbridos, respectivamente. Para cada um desses acessos, foram realizadas descrições do complemento cromossômico e idiogramas, as quais possibilitaram estabelecer relações cariotípicas entre os híbridos e seus genitores. Com base nos dados de comprimento total do cromossomo, foi estabelecida a classificação do cariótipo dos acessos com relação à simetria. Os cariótipos dos acessos de P. glaucum foram considerados simétricos, ao passo que os híbridos apresentaram cariótipos assimétricos. Para P. purpureum, dois acessos (BAGs 63 e 75) mostraram cariótipos simétricos e três (BAGs 54, 65 e 91) assimétricos. Nos híbridos interespecíficos entre P. purpureum e P. glaucum, foi possível inferir a procedência de alguns cromossomos parentais com base nas medidas de comprimento total do cromossomo, presença de satélite e morfologia do cromossomo.

Meiosis in elephant grass (Pennisetum purpureum), pearl millet (Pennisetum glaucum) (Poaceae, Poales) and their interspecific hybrids

“…Barbosa et al (2003) showed that mitotic metaphases of accessions M36 and M38 had two chromosomes with satellites but for accession M24 only one chromosome presented a satellite, indicating that there was variation among pearl millet varieties in respect to the occurrence of satellites and supporting previous work by other authors (Pantulu, 1968;Burton and Powell, 1968;Jauhar, 1981). Such variations may be attributable to chromosomal rearrangements or to mistakes in the interpretation of chromosomal morphology during mitotic analysis.…”

“…Barbosa et al (2003), in the mitotic analysis of these accessions, observed that the largest BAG 75 and BAG 91 chromosome was associated with a satellite, while for BAG 63 satellites were observed in the 1st and 4th chromosomes of the complement. The observation of three nucleolar bivalents in elephant grass ( Figure 2B) has not previously been reported by other authors.…”

Characterization of interphase nuclei from triploid hybrids between Pennisetum purpureum Schumach and Pennisetum glaucum (L.) R. Br.

“…The present results agree with those reported by Guerra (1987Guerra ( , 2000 concerning chromosome size. According to that author, species presenting chromosomes with length inferior to 3µm, such as napier grass (Barbosa et al, 2003), generally have areticulate nuclei containing condensed chromatin. In species presenting median chromosomes, ranging from 3µm to 5µm length, such as pearl millet (Barbosa et al, 2003), the heterochromatin is irregularly distributed and the nuclei are semi-reticulate.…”

“…According to that author, species presenting chromosomes with length inferior to 3µm, such as napier grass (Barbosa et al, 2003), generally have areticulate nuclei containing condensed chromatin. In species presenting median chromosomes, ranging from 3µm to 5µm length, such as pearl millet (Barbosa et al, 2003), the heterochromatin is irregularly distributed and the nuclei are semi-reticulate. For Barlow (1977) such correlation is more evident between DNA content and the interphase nucleus type.…”

“…Such hybridization results in the production of a sterile triploid hybrid (2n=3x=21), which requires a chromosomal duplication to recover fertility and make viable the use of this hybrid combination in improvement programs. Attempts of chromosomal duplication have led to the production of both hexaploid and mixoploid plants due to chromosomal elimination (Abreu et al, 2006;Barbosa et al, 2007;Campos et al, 2009).…”