Inheritance of aluminum tolerance in maize

The purpose of this study was to investigate aluminum tolerance in maize. For this purpose, a nutrient solutionwas used with the tolerant (L922) and sensitive (Ast214) homozygous parental lines, with the segregating generation F2 andwith the F2:3 lines derived thereof. Seeds were germinated on paper and seedlings transferred to a nutrient solution containing4.5 mg L-1 aluminum. In the experiments involving F2:3 derived lines groups of rows with F2:3 plants were intercropped withrows of eight seedlings of the parental lines in a completely randomized block design. Results of the F2 generation demonstrateda bimodal distribution of relative frequencies, with approximately three times more seedlings in the tolerant group. Thissuggests the participation of only one locus in tolerance inheritance. The narrow-sense heritability (F2, F2:3) of seminal rootlength of F2 plants and means of F2:3 lines was 0.49, which partially explained the bimodal frequency distribution of means ofF2:3 lines, but was not accurate enough to differentiate tolerant from sensitive groups

Heteroplasmia para o gene mitocondrial T-urf13 do citoplasma texas de milho

In maize (Zea mays L.), the Texas (T) cytoplasm carries male sterility (cms-T) and susceptibility to host-specific fungal toxins and to the insecticide methomyl, traits of great interest both for basic research and plant breeding. These traits are apparently inseparable, and they are directly associated with the T-urf13 mitochondrial gene, which encodes a 13-kilodalton protein (URF13). Reversion to male fertility, associated with toxin/methomyl resistance, has been observed in progenies of cms-T somaclones regenerated from methomyl resistant calli. Diversity for PCR amplification of T-urf13 sequence and URF13 expression was observed within revertant progenies. Apparently, this diversity occurred among tissues within ear and tassel, and between ears and tassels of individual plants. The results demonstrate heteroplasmy in T-urf13 sequence persisting through several generations of T-cytoplasm mutants, that apparently consisted of deletions and sequence alterations. Furthermore, URF13 deficiency suggested that total or partial cytoplasmic reversions to male fertility in cms-T somaclones are caused by T-urf13 heteroplasmyEm milho (Zea mays L.), o citoplasma texas (T) condiciona macho-esterilidade (cms-T) e susceptibilidade à toxina de fungos e ao inseticida metomil, características de grande interesse para estudos básicos e melhoramento de plantas. Essas características são aparentemente inseparáveis e estão diretamente associadas ao gene mitocondrial T-urf13, que codifica uma proteína de 13 kilodaltons (URF13). Reversão para fertilidade masculina, associada à resistência à toxina/metomil, tem sido observada em progênies de somaclones cms-T, derivados de calos resistentes ao metomil. Foi encontrada diversidade para amplificação via PCR do gene T-urf13 e para expressão da proteína URF13 nesses somaclones revertentes. Aparentemente, esta diversidade ocorre dentro de tecidos de espiga e panícula e entre espiga e panícula de uma mesma planta. Os resultados demonstram heteroplasmia na seqüência T-urf13, que persistiu em várias gerações desses mutantes, consistindo aparentemente de deleções e alterações na seqüência de DNA. Além disso, deficiência da proteína URF13 em somaclones férteis sugeriu que a reversão total ou parcial da macho-fertilidade é causada pela heteroplasmia no gene T-urf1

<b>Molecular variants in populations of <i>Bryconamericus</i> aff. <i>iheringii</i> (Characiformes, Characidae) in the upper Paraná river basin</b> - doi: 10.4025/actascibiolsci.v35i2.11451

There are evidences that Bryconamericus aff. iheringii represents a species complex. DNA molecular markers have been effective in studies on phylogeny, taxonomy, and identification of cryptic species. In this study, partial sequences of genes of ATPase 6 and 8 were used to assess genetic diversity within and among populations of B. aff. iheringii of sub-basins of Tibagi, Pirapó and Ivaí rivers, belonging to the Upper Paraná river basin. The analysis of the sequences of genes pointed out high genetic diversity in B. aff. iheringii from the sub-basins studied with genetic distance values comparable to those found among different species. There was a division of the individuals into five groups. The comparison with other species of Bryconamericus that have sequences available in GenBank confirmed that the individuals studied have relevant values of genetic distance, found among different species. Nevertheless, with the available data it is not possible to refute the hypothesis that the populations correspond to a group resulting from hybridization or that there might have been introgression of mitochondrial DNA among different species

Obtaining 5S rDNA molecular markers for native and invasive Cichla populations (Perciformes – Cichlidae), in Brazil - DOI: 10.4025/actascibiolsci.v30i1.1467

The 5S rDNA gene is informative and has high conservation rates along the eukaryotic genome, having unique hereditary characteristics. Molecular studies with the 5S rDNA gene have been carried out with several groups, including some species of fish, aiming at solving phylogenetic relationship problems, ancestral patterns and genetic diversity among groups in natural populations. Species of the Cichla genus, introduced in the Upper Paraná River basin, present some genetic polymorphisms detected by RAPD and SPAR analyses. These species have been intercrossing and forming viable hybrids, with greater genetic variability. The objective of this work was to standardize the amplification methodology for the non-transcribed regions of 5S rDNA multigenic family of Cichla, and to obtain specific markers for parent species that could also be identified in the hybrids. Sixty-five specimens of Cichla collected from the Upper Paraná River and Amazon basins were analyzed. Although molecular markers that could be useful in the identification of hybrids were not obtained, genetic molecular 5S rDNA species-specific markers for Cichla temensis that can be employed to identify of this species, as well population markers that can be useful in population genetic variability studies, were obtainedO gene DNAr 5S é informativo e possui altas taxas de conservação ao longo do genoma dos eucariotos, possuindo características únicas que são hereditárias. Estudos moleculares do gene DNAr 5S vem sendo realizados com diversos grupos, inclusive em algumas espécies de peixes, com o intuito de solucionar problemas de relações filogenéticas, padrão de ancestralidade e diversidade genética, entre grupos de populações naturais. Espécies do gênero Cichla, introduzidas na bacia do alto rio Paraná, apresentam polimorfismos genéticos, detectados por análise de RAPD e SPAR. Essas espécies estão intercruzando-se e formando híbridos viáveis, com maior variabilidade genética. O objetivo desse trabalho foi padronizar a metodologia de amplificação de regiões não-transcritas da família multigênica rDNA 5S de Cichla e obter marcadores específicos para as espécies parentais que pudessem, também, ser identificados nos híbridos. Foram analisados 65 espécimes de Cichla, das bacias do alto rio Paraná e Amazônica. Apesar de não se obter marcadores moleculares que pudessem ser úteis à identificação de híbridos, foram obtidos marcadores moleculares genéticos DNAr 5S espécie-específicos para Cichla temensis, que podem ser utilizados para identificação de exemplares dessa espécie e, também, marcadores populacionais, que podem ser úteis para estudos de variabilidade genética populaciona

Diferenciação genética entre populações de <em>Pseudoplatystoma corruscans</em> (Agassiz, 1829) (Osteichthyes, Pimelodidae) isoladas pelos saltos de Guaíra do rio Paraná Genetic differentiation among populations of <em>Pseudoplatystoma corruscans</em> (Agassiz, 1829) (Osteichthyes, Pimelodidae) isolated by the Guaíra Falls in the Paraná River

Os saltos de Guaíra, também denominados Sete Quedas, constituíam até 1982 uma barreira para a dispersão de peixes migradores. Este trabalho teve por objetivo verificar se populações de <em>Pseudoplatystoma corruscans</em> (Osteichthyes, Pimelodidae) eram isoladas pelos saltos de Guaíra. Amostras provenientes da planície de inundação do alto rio Paraná (PL), do reservatório Itaipu (IT) e de jusante de Yacyretá (YA), foram comparadas por RAPD. O <em>F_ST</em> de Lynch foi significativo entre PL e IT (0,090) e PL e YA (0,112). O fluxo gênico estimado (<em>Nm</em>) variou de 2,0 entre PL e YA a 8,1 entre IT e YA, e a distância genética de Nei de <em>D =</em> 0,0638 entre PL e YA a <em>D =</em> 0,0174 entre IT e YA. Estes resultados indicam existência de diferenciação genética e que, possivelmente, Sete Quedas isolavam reprodutivamente as populações. Sugerem, também, a possibilidade de áreas diferentes de desova, impedindo parcialmente a homogeneização genética das populações IT e PL.<br>Until 1982, the Guaíra Falls, also named the Seven Falls, constituted a barrier to the dispersion of migratory fish in the Paraná River. The objective of this work was to verify if populations of <em>Pseudoplatystoma corruscans</em> (Osteichthyes, Pimelodidae) were isolated by the Guaíra Falls. Samples from the Upper Paraná River floodplain (PL), the Itaipu reservoir (IT), and downstream Yacyretá reservoir (YA) were compared by RAPD markers. Lynch's <em>F_ST</em> was significant between PL and IT (0.090), and PL and YA (0.112). Estimated gene flow (<em>Nm</em>) varied from 2.0 between PL and YA to 8.1 between IT and YA. Nei's genetic distance varied from <em>D =</em> 0.0638 between PL and YA to <em>D =</em> 0.0174 between IT and YA. These results indicate the existence of genetic differentiation and that, possibly, the Guaíra Falls isolated the populations reproductively. They also suggest the possibility of different spawning areas, partially avoiding the genetic homogenization of the IT and PL populations

Identificação do gene mcyA em florações naturais de Radiocystis fernandoi, em um tributário do reservatório de Rosana, Brasil - doi: 10.4025/actascibiolsci.v33i3.6802

Cyanobacterias are known as toxin producers. Within the same species, toxic and non-toxic varieties can be found and it is impossible to differentiate them only by morphology. The most important toxin produced by cyanobacteria is microcystin. This protein is synthesized by a cluster of genes known as mcy. The detection of these genes by PCR allows the differentiation of the producing toxin strain from the non-producing toxin strain. Thus, the goal of this work was to investigate the occurrence of toxigenic blooms of cyanobacteria in the Corvo River through PCR amplification of mcyA gene. For this, two samples of blooms of cyanobacteria were collected in Corvo River. Both samples were dominated by Radiocystis fernandoi and presented positive results for the presence of the mcyA gene, which may confirm the potential toxigenicity for that species. These results are an alert about water quality in the Corvo River. Here we demonstrate that amplification of the mcyA gene by PCR is a fast, cheap and efficient method for the detection of toxin- producing cyanobacteria.As cianobactérias são conhecidamente produtoras de toxinas. Dentro de uma mesma espécie, podemos encontrar variedades tóxicas e não-tóxicas, impossíveis de diferenciação apenas pela morfologia. A principal toxina produzida pelas cianobactérias é a microcistina. Esta proteína é biossintetizada por um grupo de genes conhecidos como mcy. A detecção destes genes a partir de PCR permite a distinção das variedades tóxicas e não-tóxicas. Desse modo, o objetivo desse trabalho foi investigar a ocorrência de florações produtoras de toxinas em um rio tributário do reservatório de Rosana, via amplificação do gene mcyA por PCR. Foram coletadas duas amostras de água da subsuperfície. As duas amostras coletadas no rio do Corvo foram dominadas pela espécie Radiocystis fernandoi e apresentaram resultados positivos para a presença do gene mcyA, confirmando o potencial tóxico dessa espécie. Os resultados representam alerta sobre a qualidade da água do rio do Corvo. A técnica PCR foi eficiente para a rápida detecção de cianobactérias produtoras de toxinas, inclusive podendo ser utilizada antes mesmo do agravamento das condições ambientais pela produção de toxinas, além de apresentar baixo custo

Obtaining 5S rDNA molecular markers for native and invasive Cichla populations (Perciformes – Cichlidae), in Brazil = Obtenção de marcadores moleculares 5S rDNA para populações nativas e introduzidas de Cichla (Perciformes – Cichlidae), do Brasil

The 5S rDNA gene is informative and has high conservation rates along the eukaryotic genome, having unique hereditary characteristics. Molecular studies with the 5S rDNA gene have been carried out with several groups, including some species of fish, aiming at solving phylogenetic relationship problems, ancestral patterns and geneticdiversity among groups in natural populations. Species of the Cichla genus, introduced in the upper Paraná river basin, present some genetic polymorphisms detected by RAPD and SPAR analyses. These species have been intercrossing and forming viable hybrids, withgreater genetic variability. The objective of this work was to standardize the amplification methodology for the non-transcribed regions of 5S rDNA multigenic family of Cichla, and to obtain specific markers for parent species that could also be identified in the hybrids. Sixty-five specimens of Cichla collected from the upper Paraná river and Amazon basins were analyzed. Although molecular markers that could be useful in the identification of hybrids were not obtained, genetic molecular 5S rDNA species-specific markers for Cichla temensis that can be employed to identify of this species, as well population markers that can be useful in population genetic variability studies, were obtained.O gene DNAr 5S é informativo e possui altas taxas de conservação ao longo do genoma dos eucariotos, possuindo características únicas que são hereditárias. Estudos moleculares do gene DNAr 5S vem sendo realizados com diversos grupos, inclusive em algumas espécies de peixes, com o intuito de solucionar problemas de relações filogenéticas, padrão de ancestralidade e diversidade genética, entre grupos de populações naturais. Espécies do gênero Cichla, introduzidas na bacia do alto rio Paraná, apresentam polimorfismos genéticos, detectados por análise de RAPD e SPAR. Essas espécies estão intercruzando-se e formando híbridos viáveis, com maior variabilidade genética. O objetivo desse trabalho foi padronizar ametodologia de amplificação de regiões não-transcritas da família multigênica rDNA 5S de Cichla e obter marcadores específicos para as espécies parentais que pudessem, também, ser identificados nos híbridos. Foram analisados 65 espécimes de Cichla, das bacias do alto rio Paraná e Amazônica. Apesar de não se obter marcadores moleculares que pudessem ser úteis à identificação de híbridos, foram obtidos marcadores moleculares genéticos DNAr 5S espécie-específicos para Cichla temensis, que podem ser utilizados para identificação deexemplares dessa espécie e, também, marcadores populacionais, que podem ser úteis para estudos de variabilidade genética populacional

Spar genetic analysis of two invasive species of Cichla (Tucunaré) (Perciformes: Cichlidae) in the Paraná river basin - doi: 10.4025/actascibiolsci.v33i1.4855

The introduction of exotic species in lake ecosystems has been greatly highlighted in the literature worldwide. Since introduction may threaten diversity of native fish, the issue turns up to be of paramount importance. Ecological effects may be predation, competition, parasitism or genetic, that is, changes in the genetic pool of populations owing to the occurrence of hybrids. Although the Tucunaré fish (Cichla) is native to the Amazon region, it can be found in other hydrographic basins in which it has been introduced. RAPD molecular marker research showed that there are two species (Cichla kelberi and C. piquiti) belonging to the genus Cichla in the rivers of the Paraná basin. Different morphotypes in the region may also be due to hybridization. Current research used SPAR molecular markers to confirm the presence of hybrids and the rupture of isolation mechanisms. Seventy-two specimens collected in several sites of the river Paraná and Amazon basins were analyzed. Since exclusive SPAR molecular markers were obtained for Cichla kelberi and C. piquiti populations, the introduction of the two species in the region has been confirmed. Identification of the markers in specimens of the Paraná river basin confirmed hybridization between these exotic species.The introduction of exotic species in lake ecosystems has been greatly highlighted in the literature worldwide. Since introduction may threaten diversity of native fish, the issue turns up to be of paramount importance. Ecological effects may be predation, competition, parasitism or genetic, that is, changes in the genetic pool of populations owing to the occurrence of hybrids. Although the Tucunaré fish (Cichla) is native to the Amazon region, it can be found in other hydrographic basins in which it has been introduced. RAPD molecular marker research showed that there are two species (Cichla kelberi and C. piquiti) belonging to the genus Cichla in the rivers of the Paraná basin. Different morphotypes in the region may also be due to hybridization. Current research used SPAR molecular markers to confirm the presence of hybrids and the rupture of isolation mechanisms. Seventy-two specimens collected in several sites of the river Paraná and Amazon basins were analyzed. Since exclusive SPAR molecular markers were obtained for Cichla kelberi and C. piquiti populations, the introduction of the two species in the region has been confirmed. Identification of the markers in specimens of the Paraná river basin confirmed hybridization between these exotic species