Antônio Vander Pereira

Repeatability of elephantgrass forage traits

The repeatability coefficient is widely used by geneticists as a measure of the upper limit of the heritability and as an efficient tool for predicting genotype value from successive measurements on individuals. It also allows to estimate whether the number of evaluations is sufficient to determine genotype superiority within a certain degree of reliability. The purpose of this research was to evaluate the coefficient of repeatability of crude protein concentration on stems and leaves, in 77 accesses of the Embrapas Elephantgrass Germplasm Active Bank. The experimental design consisted of was randomized blocks, with two replicates. Forage was cut on 30, 45, 60 and 75 days of croping, using 15 sprouts of each experimental unit. ANOVA was performed for each trait data set, and genetic and environmental parameters were determined. The repeatability coefficients were estimated by the methods: Analysis of variance, principal components - correlation matrix, principal components - co-variance matrix and structural analysis - correlation matrix. Genetic variability was found among the genotypes for the appraised traits, which allowed the identification of genetically superior material that can be used in breeding programs. The coefficients of estimated repeatability were not different for the traits studied. Four cuts were enough for a coefficient of determination of 0.80, for all the methods. The use of seven cuts may enable predictions with 0.90 reliability for the studied traits, using any method.

Avaliação de cultivares de alfafa e estimativas de repetibilidade de caracteres forrageiros

The objective of this study was to evaluate the performance of 42 cultivars of alfalfa (Medicago sativa L.) and to estimate the repeatability coefficient for dry matter production, leaf and stem protein content and disease tolerance features during the dry (April to September) and rainy (October to March) seasons with six cuts. Dry matter yield and leaf protein content presented signifi- cant variation in both seasons, although stem protein content and tolerance to diseases were different only during the dry season. Cultivars Crioula and Cibola had the best performance in most features. In general, the repeatability coefficient showed a low magnitude estimate (below 0,40). Regarding dry matter production, the cultivars showed similar behavior in both seasons, with repeatability coeffi- cient ranging from 0.3195 to 0.4270, genotypic determination around 65% and the possibility to predict the real value after seven to nine cuts.

Avaliação agronômica de híbridos interespecíficos entre capim-elefante e milheto

O objetivo deste trabalho foi avaliar o comportamento agronomico de hibridos entre capim-elefante (Pennisetum purpureum Schum.) e milheto (P. glaucum (E.) Leek), a fim de determinar seu potencial para o melhoramento da forragem e a selecao de hibridos para futuras avaliacoes. Foram utilizadas 12 cultivares de milheto e 11 clones de capim-elefante, cruzados em esquema de dialelo parcial. As 132 combinacoes hibridas, alem de duas testemunhas, foram avaliadas em experimentos em blocos casualizados, com tres repeticoes. Anotaram-se dados de producao de materia seca, altura de plantas, porcentagem de materia seca, relacao entre folha e caule e de qualidade da forragem (porcentagem de proteina bruta, porcentagem de fibra em detergente neutro e acido e digestibilidade in vitro da materia orgânica). Foi verificada existencia de variabilidade entre os hibridos interespecificos de capim-elefante e milheto, na maioria das caracteristicas. A superioridade de alguns hibridos, em relacao as testemunhas, demonstra o potencial do cruzamento entre P. purpureum e P. glaucum para a obtencao de cultivares melhoradas. Considerando-se tanto caracteristicas de producao como de qualidade da forragem, os melhores hibridos avaliados foram 108 (F91-2-5 x M-60), 53 (F93-4-2 x M-27), 35 (F94-28-3 x M-42), 36 (F94-28-3 x M-60) e 4 (F92-101-2 x M-35).

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

Foram realizados estudos citogeneticos em quinze acessos do Banco de Germoplasma Forrageiro, da Embrapa Gado de Leite, sendo cinco hibridos interespecificos de Pennisetum purpureum e Pennisetum glaucum e seus genitores. As analises citogeneticas mitoticas realizadas mediante coloracao com reativo de Schiff confirmaram o numero cromossomico de 2n =14, 28 e 21 para os acessos de P. glaucum, P. purpureum e hibridos, respectivamente. Para cada um desses acessos, foram realizadas descricoes do complemento cromossomico e idiogramas, as quais possibilitaram estabelecer relacoes cariotipicas entre os hibridos e seus genitores. Com base nos dados de comprimento total do cromossomo, foi estabelecida a classificacao do cariotipo dos acessos com relacao a simetria. Os cariotipos dos acessos de P. glaucum foram considerados simetricos, ao passo que os hibridos apresentaram cariotipos assimetricos. Para P. purpureum, dois acessos (BAGs 63 e 75) mostraram cariotipos simetricos e tres (BAGs 54, 65 e 91) assimetricos. Nos hibridos interespecificos entre P. purpureum e P. glaucum, foi possivel inferir a procedencia de alguns cromossomos parentais com base nas medidas de comprimento total do cromossomo, presenca de satelite e morfologia do cromossomo.

Seleção de genótipos de capim-elefante quanto à resistência à cigarrinha-das-pastagens

The objective of this work was to evaluate genotypes of elephant grass (Pennisetum purpureum Schum.) regarding resistance to the spittlebug Mahanarva spectabilis. For antibiosis evaluation, each plant was infested with six eggs near hatching, thirty days after planting, in a completely randomized design with 30 genotypes and ten repetitions. Forty-five days after the nymphs hatched, the insect survival rate was evaluated on the different genotypes. For nonpreference mechanism evaluation, the size and number of the nymphs per pot were assessed every 15 days, in plants kept at greenhouse, where adults of M. spectabilis were periodically released, in a completely randomized design, with three repetitions per genotype in two sampling periods. Cameroon de Piracicaba, Pioneiro, Cuba 169, Santa Rita, Mineiro Ipeaco, Mercker Comum de Pinda and CNPGL 96-27-3 genotypes were selected for resistance, by antibiosis mechanism. In the study of the nonpreference mechanism, the number and average size of the nymphs varied significantly as a function of the elephant grass genotype. Roxo de Botucatu and Pioneiro genotypes are, respectively, susceptible and resistant check candidates by the antibiosis mechanism, and Cameroon and Cameroon Piracicaba genotypes are promising by the nonpreference mechanism.

Cytotaxonomy of some species and of interspecific hybrids of Pennisetum (Poaceae, Poales)

Cytotaxonomic studies were carried out on 26 accessions of Pennisetum spp. originating from the Active Germplasm Bank of Embrapa Gado de Leite-Juiz de Fora, Minas Gerais, Brazil.This study presents cytogenetics and reproductive morphological data for each one of these accessions, which allowed groupings and suggest botanical identifications to be established. The metaphases of the accessions characterized as P. purpureum confirmed the presence of 2n = 28 chromosomes that have already been described for this species. For the hybrids between P. purpureum and P. glaucum and for the hexaploids, resulting from the chromosome duplication of these hybrids, 2n = 21 and 2n = 42 chromosomes were confirmed, respectively. The wild accession identified as P. setosum showed metaphases with 2n = 54 chromosomes, while those characterized as P. nervosum had cells with 2n = 36 chromosomes. The wild accession 15 was different from the others for the morphological characters, with 2n = 36 chromosomes, and was classified as P. orientale. Two statistical procedures were used (canonical variables and cluster analysis on the basis of the Mahalanobis distance), and the results confirmed the conclusions obtained from the cytogenetic and morphologic analysis.

Potencial forrageiro de novos clones de capim-elefante

The objective of this experiment was to evaluate the forage potential of new selected clones of elephantgrass. The evaluation was conducted at the Dairy Cattle Research Centre - EMBRAPA, Coronel Pacheco, Minas Gerais, for two consecutive years. Twenty selected clones obtained by the elephantgrass breeding program were evaluated, and two traditional cultivars Cameroon and Taiwan A -146 were used as control. The experimental procedure was a randomized block design with four replicates. The fertilization for both establishment and maintenance was applied according to the soil chemical analysis and elephant grass nutritional requirements. Significant differences among the clones were observed regarding to forage production potential, leaf:stem ratio, and aerial and basal tillering. The majority of the evaluated new clones were superior to the traditional cultivars Cameroon and Taiwan A-146 with relation to dry matter production during the dry and rainy periods. Crude protein content in the forage did not differ among the new clones and the control cultivars (Cameroon and Taiwan A-146), during both dry and rainy seasons. The clone F 27-01, released as elephant grass cultivar Pioneiro, was superior for the most evaluated agronomic traits.

Análise de trilha de caracteres forrageiros do capim-elefante (Pennisetum purpureum Schum.)

The main goals of this work was to obtain estimates of phenotype, genotype and residual correlation coefficients and display genotype correlations in direct and indirect effects (path analysis) of height, diameter of stem at the base and number of tillers per meter (explanatory independent variables) on dry matter production (basic dependent variable) of elephantgrass clones in two harvest periods at conditions of northern Rio de Janeiro State, Brazil. Great differences among estimates in two harvest periods were observed, however it could be concluded that height of plants at cutting influenced dry matter production mainly in conditions of high tillering capable clones. Number of tillers per meter and diameter of stem explained better dry matter production potential, acting, respectively, in an direct and inverse way, alternating according to environmental conditions during growth.

Duplicação cromossômica de híbridos triplóides de capim-elefante e milheto

ABSTRACTCHROMOSE DUPLICATION OF TRIPLOID HYBRIDS BETWEEN ELEPHANTGRASSAND PEARL MILLET The aim of this study was to duble the chromose number of elephantgrass and pearl millet triploidhybrids in order to obtain hexaploid fertile plants. This strategy would allow the use of the hexaploidsin the elephantgrass breeding program as a bridge for transfering alleles of desired characteristics andmaking possible propagation by seed. Seedlings, plantlets and stem segments were cultivated in vitroand treated with 0.05% or 0.1% colchicine for 12 or 24 h. Seedlings of different hybrid genotypes andmeristems of two interspecific hybrids were cultivated in vivo and treated for 24 h with 0.05% colchicine.Chromose duplication was confirmed by countings in the root tip cells. Pollen viability, in vitro ( 1 ) Recebido para publicacao em 13 de junho de 2006 e aceito em 22 de marco de 2007.( 2 ) Departamento de Ciencias Biologicas, Universidade Federal de Alfenas, UNIFAL-MG, Rua Gabriel Monteiro da Silva, 714,Centro, 37130-000 Alfenas (MG), Brasil. E-mail: sandro@unifal-mg.edu.br (*) Autor correspondente.(

Mixoploidia em híbridos de capim-elefante x milheto tratados com agentes antimitóticos

The objective of this work was to evaluate methods of chromosome duplication, using antimitotic agents and several botanical materials as explant hybrids between napiergrass (Pennisetum purpureum Shum.) and pearl millet (Pennisetum glaucum (L.) R. Br.). Colchicine (50 mg L-1 and 100 mg L-1) and cycloheximide:8-hydroxyquinoline (1:1) (25 mg L-1:300 mg L -1) solutions have been applied in vivo to shoots and in vitro to seedlings and tillers. The antimitotic effect has been evaluated through survival rate, chromosome number and presence of cell cycle anomalies at the root tips of surviving plants. The best results have been obtained when seedlings have been treated with colchicine and tillers with cycloheximide: 8-hydroxyquinoline. Mixoploidy has been observed in cells having 14 to 42 chromosomes, indicating that duplication, followed by chromosome elimination, has occurred, which has been confirmed by chromosome aberrations. In the average, 86.4% of the analyzed cells have presented a chromosome number different from 21.