Samuel Pereira de Carvalho

Avaliação de caracteres quantitativos relacionados com o crescimento vegetativo entre cultivares de café arábica de porte baixo

O objetivo deste trabalho foi estudar associacao entre caracteres quantitativos relacionados com o crescimento vegetativo em cultivares de porte baixo de cafe arabica (Coffea arabica L.). O experimento foi desenvolvido na Unidade Experimental da Empresa Pernambucana de Pesquisa Agropecuaria (IPA), municipio de Brejao (PE), localizado na mesorregiao do agreste e na microrregiao de Garanhuns, no ano agricola de 2004/2005. O delineamento usado foi em blocos ao acaso, com quatro blocos e doze tratamentos constituidos por cultivares de porte baixo. Os caracteres foram avaliados atraves da analise de variância, estimativa dos parâmetros dos componentes da covariância e determinismo genetico e dos coeficientes de correlacoes. Os resultados detectaram nas cultivares estudadas diferencas para altura das plantas e comprimento dos ramos palagiotropicos. As cultivares Topazio MG 1189, Catucai, Obata IAC 1669-20 e Topazio MG 1190 sao as melhores em desenvolvimento nos 12 primeiros meses de crescimento. O diâmetro de caule esta fortemente correlacionado positivamente com o comprimento de ramos plagiotropicos quando avaliada o incremento de crescimento. Quando avaliada aos 12 meses, o carater altura de plantas correlacionou-se negativa e altamente significativa com o diâmetro de copa e o comprimento dos ramos plagiotropicos, negativamente a numero de ramos plagiotropicos secundarios e positivamente com o numero de internodios de ramos plagiotropicos.

Caracterização morfoagronômica e coeficientes de trilha de caracteres componentes da produção em mandioca

The objectives of this work were to perform the agronomic characterization of 100 cassava plants (Manihot esculenta Crantz) and to obtain path coefficients analysis between the storage root production (basic variable) and five production components (explanative variable). The experiment was conducted at a research farm of Universidade Federal de Lavras, Minas Gerais State, Brazil, in square lattice (10x10), with two replications, using 100 clones and four plants per plot. Statistical analyses were accomplished considering the eight characteristics individually. The Scott-Knotts test was used for grouping the means. Clones 87 and 88 showed to be promising both to be used in crossings and to be fixed as new cultivate, due to their excellent performance in the characteristics: length, number and storage roots production per plant. Path coefficient analysis demonstrates that root number per plant and aerial part weight can be used as criteria of indirect selection for storage roots production.

Seleção de progênies F4 de cafeeiros obtidas pelo cruzamento de Icatu com Catimor

The objective of this work was to select progenies of productive and rust resistant coffee plants. An experiment was installed and carried out in Machado, MG, Brazil, where 29 progenies obtained from the Icatu x Catimor cross were evaluated and selected by the coffee plant genetic improvement program coordinated by EPAMIG. Cultivar Ruby MG 1192 was used as control. The experiment was arranged in a randomized block design with three repetitions. Production of processed coffee in 60 kg bags.ha-1 from six harvests, from 2001/2002 to 2006/2007, vegetative vigor evaluated after the 2006/2007 harvest and the incidence and severity of rust in the first semester of 2006 were analyzed. Variability was observed for production and rust resistance, which was confirmed by heredability estimates of good magnitude, varying from 58.5% for production to 92.6% for rust incidence. These results allied to good production means, low rust incidence and severity and good vegetative vigor of some progenies, show that it is possible to select superior progenies on the basis of production and rust resistance.

Anatomia foliar de mandioca em função do potencial para tolerância à diferentes condições ambientais

Cassava is an important plant, cultivated in tropical regions, possessing great genetic variability which has still hardly been studied. The objective of this work was to examine the leaf anatomy of thirteen genotypes to assess their potential for adaptation in different environmental conditions. Fully unfolded leaves were collected from thirteen cassava genotypes being analyzed for quantitative changes in internal structure using optical microscopy. The experimental design was completely randomized with 12 replications and 13 treatments, the data were submitted to ANOVA and the Scott-Knott test. The different genotypes displayed great anatomical plasticity for most characters, with the most important changes occurring in the density and size of the stomata, tissue thickness of the abaxial epidermis, of the palisade and spongy parenchyma, in the phloem and xylem. The UFLA E, IAC 14 and UFLA J genotypes displayed as possibilities for xeric conditions, due to a high stomatal density, smaller stomata, a thicker adaxial epidermis, thicker palisade and spongy parenchyma, lower vulnerability of the xylem and greater thickness of the phloem, which would allow reduction in transpiration and better use of a large amount of incident radiation. The other genotypes exhibit more mesophytic features. Thus, cassava genotypes have anatomical plasticity, and can display the potential for selection of desirable characteristics for different environmental conditions.

Importância das interações cultivares x locais e cultivares x anos na avaliação de milho na safrinha

Com o objetivo de verificar a importância da interacao cultivares x locais e cultivares x anos e de identificar entre os hibridos ja disponiveis os que sejam mais adaptados e estaveis para o cultivo em safrinha, foram estimados os parâmetros de adaptabilidade e estabilidade a partir de dados obtidos em experimentos de avaliacao de cultivares de milho na safrinha, nos anos de 1993, 1994 e 1995. Esses experimentos foram conduzidos nos Estados de Sao Paulo, Goias e Parana. O delineamento utilizado foi em blocos casualizados com tres repeticoes. Constatou-se que a magnitude da variância da interacao cultivares com anos dentro de locais foi mais expressiva do que entre locais, o que indica a necessidade de que as avaliacoes de cultivares na safrinha sejam realizadas num maior numero de anos. As cultivares diferiram quanto a adaptabilidade e estabilidade de producao de graos. Os materiais que se destacaram como mais adaptados e estaveis foram o hibrido simples Zeneca 8452, o hibrido triplo C 805 e o hibrido duplo Agromen 2012. Ja os hibridos duplos BR 201, Planagri 411, AG 303 e C 125 foram os que mostraram menor adaptacao e maior instabilidade.

Divergência genética entre cafeeiros do germoplasma Maragogipe

This study aimed to identify the genetic divergence among coffee trees of the Maragogipe group in the active germplasm coffee bank in Patrocinio, Minas Gerais, Brazil, using multivariate analyzes. In the study, 27 morpho-agronomical descriptors were assessed. Mahalanobis generalized distance was applied to quantify the genetic divergence among genotypes. The following methods were used: Tocher clustering, Unweighted Pair-Group Method Using Arithmetic Averages (UPGMA) hierarchical clustering and the canonical variables analysis. The cluster analysis by Tocher method and the UPGMA separated the accessions into three and six groups, respectively. The analysis of the relative contribution of each characteristic to the genetic dissimilarity highlighted the intensity of curling leaf, inflorescence number per leaf axil and average yield as those that contributed most to the achievement of genetic divergence. It was observed that the first three canonical variables explained more than 90% of the total variance contained in the set of the analyzed characteristics. The combination between MG0167 and MG0170 accessions is the most promising for a possible crossing for immediate use in breeding programs.

Estimating gain by use of a classic selection index under multicollinearity in wheat (Triticum aestivum)

It was shown that the classic selection index, under multicollinearity, could not give simultaneous gains for wheat grain production and its primary components. This was due to the instability and, consequently, low precision of the coefficient index estimates. A modification of the prediction process of the index was proposed to avoid the adverse effects of multicollinearity, adopting a procedure based on ridge regression theory. The modified classic selection index, or ridge index, gave more statistically viable index coefficient estimates and gains for all of the characters evaluated. However, lower gains for number of grains per spike and grain yield were obtained, when compared to those obtained with selection for grain yield.

Avaliação da diversidade genética entre acessos de mamoneira (Ricinus communis L.) por meio de caracteres morfoagronômicos

Genetic divergence is one of the most important breeding parameters evaluated in the initial phase of a genetic improvement program. The objective of this work was to characterize 15 accessions of castor bean using morphoagronomic traits. The trial was carried out in Lavras, MG, Brazil, from February to August 2008. The experimental design was a randomized complete block design with three replicates and 25 plants per plot. The traits evaluated were: plant height (cm), stem height (cm), number of nodes, diameter of stem and number of clusters. Significant differences (F test: P < 0.01) were found for accession effects on all studied traits. Genetic distances among accessions were estimated using the Euclidean method. Four distinct groups were formed using the methods of Tocher and the hierarchical nearest neighbor clustering, based on the Euclidean distance. The results of this work indicate crossings between accessions from groups I and IV, II and IV and III and IV.

Genetic variability among cassava accessions based on SSR markers

Objetivou-se caracterizar e estimar a similaridade genetica entre 93 acessos de mandioca. A amplificacao do DNA foi realizada com 14 primers microssatelites. Os produtos de amplificacao foram separados por eletroforese em gel de poliacrilamida, evidenciando-se a formacao de bandas polimorficas, por meio das quais os acessos foram discriminados. A similaridade genetica entre os acessos de mandioca foi estimada por meio do coeficiente de Dice. A analise de agrupamento foi feita com o metodo UPGMA. 26 alelos foram amplificados com 2 a 4 alelos por loco. O coeficiente de similaridade genetica variou de 0,16 a 0,96. Os valores medios para heterozigosidade observada e esperada foram 0,18 e 0,46, respectivamente. 20 agrupamentos de similaridade genetica foram detectados, demonstrando a existencia de diversidade entre os acessos, sugerindo a possibilidade de geracao de hibridos heteroticos.

Observações anatômicas em plantas de Coffea arabica L. obtidas por enraizamento de estacas

Uma forma para se obter diminuicao significativa de tempo e recursos despendidos nos programas de melhoramento de Coffea arabica L. e a clonagem de hibridos F1 por meio de estacas caulinares. Alguns estudos, em diferentes instituicoes, foram realizados buscando-se definir um metodo eficiente para esse tipo de clonagem. Com o objetivo de verificar-se a presenca de barreiras anatomicas ao enraizamento de estacas caulinares do cafeeiro e a origem das raizes adventicias, bem como compara-las as raizes provenientes de plantas obtidas por semeadura, foram realizadas analises anatomicas no Departamento de Biologia da Universidade Federal de Lavras (UFLA), Lavras, MG. Utilizaram-se estacas caulinares de cafeeiro dos cultivares Acaia e Rubi e mudas obtidas por semeadura direta e por estaquia. Os cortes realizados nas estacas caulinares mostraram nao existirem barreiras anatomicas ao enraizamento adventicio. Nas estacas enraizadas, a origem do primordio radicular foi proxima aos tecidos vasculares. Cortes histologicos nas raizes formadas nas estacas e nas raizes de mudas obtidas por semeadura confirmaram que elas apresentam as mesmas estruturas primarias.