João Bosco dos Santos

Comparison of similarity coefficients based on RAPD markers in the common bean

The alterations caused by eight different similarity coefficients were evaluated in the clustering and ordination of 27 common bean (Phaseolus vulgaris L.) cultivars analyzed by RAPD markers. The Anderberg, simple matching, Rogers and Tanimoto, Russel and Rao, Ochiai, Jaccard, Sorensen-Dice, and Ochiai IIs coefficients were tested. Comparisons among the coefficients were made through correlation analysis of genetic distances obtained by the complement of these coefficients, dendrogram evaluation (visual inspection and consensus fork index - CIC), projection efficiency in a two-dimensional space, and groups formed by Tochers optimization procedure. The employment of different similarity coefficients caused few alterations in cultivar classification, since correlations among genetic distances were larger than 0.86. Nevertheless, the different similarity coefficients altered the projection efficiency in a two-dimensional space and formed different numbers of groups by Tochers optimization procedure. Among these coefficients, Russel and Raos was the most discordant and the Sorensen-Dice was considered the most adequate due to a higher projection efficiency in a two-dimensional space. Even though few structural changes were suggested in the most different groups, these coefficients altered some relationships between cultivars with high genetic similarity.

Genetic progress after four cycles of recurrent selection for yield and grain traits in common bean

The objective of this study was to evaluate the genetic progress after four cycles of recurrent selection in common bean. The base segregating population was obtained from 10 parents, and derived the S0:1 and S0:2 families that were evaluated. The S0:3 families with higher grain yield and grain color, like the standard carioca were selected, and were intercrossed to generate the population of the following cycle. This process was repeated for four cycles. The best families were evaluated in each cycle by many generations and locations, and the five best lines of each cycle were identified. The 20 lines thus obtained were evaluated in two growing seasons, sown in July and November 2002. The grain yield (kg/ha) and grain type (scale of scores) were evaluated. Genetic progress was confirmed for both traits. The mean annual gain with selection for the grain type was 10.5% and 5.7% for grain yield, with no evidence of variability reduction in the population. These results show that recurrent selection is a good alternative for improving common bean quantitative traits.

Diversidade genética entre acessos de açaizeiro baseada em marcadores RAPD

One characterized the genetic diversity among accessions of assai palm using RAPD markers. One hundred and sixteen accessions conserved in the Embrapa Eastern Amazon germplasm collection, in Belem, PA, were analyzed using 28 primers. The data of the binary matrix were used to estimate the genetic dissimilarities using the arithmetical complement of Dice similarity coefficient and also for the bootstrap analysis. The genetic dissimilarities were represented in a dendrogram generated by the UPGMA method. The primers revealed 263 polymorphic RAPD loci presented wide genetic diversity among the accessions, varying from 0,06 to 0,67, being two accessions of the Chaves, PA the most divergent. But, some accessions of the same origin presented low dissimilarities. The dendrogram allowed the formation of eight groups delimited by the genetic mean dissimilarity (dgm: 0,40): two formed by a single accession; two constituted by two accessions and the others for several sub-groups with accessions of different origin. The ideal number of bands for estimating the genetic diversity among 116 accessions was 180. Therefore, the number of bands used in this study was efficient to characterize with precision the genetic relationship among the accessions of assai palm. The accessions divergent should be useful in the formation of nuclear collections and genetic breeding.

Variabilidade genética de isolados do cogumelo Agaricus blazei por meio de marcadores RAPD

Agaricus blazei (Murrill) ss. Heinem. e um cogumelo nativo do Brasil que vem despertando a atencao de varios pesquisadores em todo o mundo, devido as suas propriedades farmacologicas e nutricionais. Este trabalho teve por objetivo, analisar a variabilidade genetica de alguns isolados utilizados comercialmente, por meio de marcadores RAPD. Foram analisados nove isolados de A. blazei, provenientes de diferentes regioes do Brasil e, como controle, dois isolados de A. bisporus. Todos eles fazem parte da colecao de fungos do Laboratorio de Cogumelos Comestiveis e Medicinais do DBI/UFLA. Diferentes primers aleatorios foram utilizados, gerando um total de 139 bandas polimorficas. Procedeu-se a avaliacao de similaridade genetica entre os isolados pelo coeficiente de Dice e analise de agrupamento pelo metodo UPGMA. Os resultados revelaram que dos 9 isolados de A. blazei, 6 (CS1, CS3, CS4, CS6, CS8 e CS9) apresentaram uma alta similaridade genetica, sendo considerados isolados de uma mesma origem ou clones. O isolado CS2 foi o que apresentou a maior divergencia genetica em relacao aos demais, seguido dos isolados CS5 e CS7, os quais formaram cada um, um grupo a parte, com medias de 60,6%, 88,7% e 91,3% de similaridade genetica, respectivamente.

Choice of common bean parents based on combining ability estimates

The obtention of genetically improved cultivars is the main objective of breeding programs, whose efficiency is increased by a careful choice of parents. Based on both general (GCA) and specific (SCA) combining abilities for grain yield, the purpose of this research was to choose the most promising populations of common beans, for line selection. GCA and SCA were measured by means of a complete diallel without reciprocals, using twelve cultivars/lines. Parents and corresponding F2 segregating populations were evaluated for grain yield by a 9 x 9 triple square lattice design. It was found that the segregating populations differed in grain yield, with predominant SCA effects, but with significant GCA effects as well. Among the populations derived from parents with positive GCA values, Apore x CI-128, CI-128 x Perola, PF-9029975 x Ouro Negro, and CI-128 x Ouro Negro also showed positive SCA values and high grain yields, therefore being the most promising populations for grain yield improvement. The highest values of specific combining ability were observed in populations H-4-7 x ESAL 693, CI-128 x Perola, and A-285 Ruda x IAC Carioca Arua, which must be the most segregating ones. Hybrid combinations with a high SCA deriving from at least one parent with high GCA were: Perola x CI-128 and Ouro Negro x Perola. Although line ESAL 693 presented the lowest GCA value, one of its derived populations, ESAL 693 x H-4-7, had the highest SCA and heterosis values. The high correlation between heterosis and SCA indicates that heterosis can be useful when SCA is not available.

Linhagens de feijoeiro com resistência à antracnose selecionadas quanto a características agronômicas desejáveis

O objetivo deste trabalho foi identificar entre as linhagens de feijoeiro resistentes a antracnose, aquelas com alta produtividade, tipo de graos Carioca, resistencia a mancha-angular (Phaeoisariopsis griseola) e porte arbustivo. Foram avaliadas 256 linhagens oriundas de um programa de melhoramento genetico por retrocruzamentos. Quatro experimentos foram conduzidos em tres locais no Estado de Minas Gerais, em que foram avaliadas a producao e o tipo de graos, o porte e a reacao a mancha-angular. Observaram-se acentuadas diferencas geneticas entre as linhagens e, consequentemente, as herdabilidades foram tambem elevadas e propiciaram acentuados ganhos com a selecao. A maioria das correlacoes fenotipicas estimadas entre os caracteres nao foi significativa, indicando a possibilidade de selecao de linhagens superiores em todos os fenotipos de interesse. Foram selecionadas cinco linhagens com alto potencial produtivo, graos do tipo Carioca, porte arbustivo e maior nivel de resistencia a mancha-angular, sendo que duas delas possuem uma pirâmide de alelos de resistencia a antracnose.

DIVERGÊNCIA GENÉTICA ENTRE GENÓTIPOS DE FEIJOEIRO A PARTIR DE TÉCNICAS MULTIVARIADAS

Multivariate techniques were used to evaluate the genetic divergence among genotypes of common bean, aiming to identify segregating populations with large genetic variability. The multivariate techniques used were: the average Euclidean distance based on standardized variables (de), on scores of the three first canonical variables (dvc), on scores of the first three principal components (dcp), on the first three factor loads (dft), and the Mahalanobis generalized distance (D2). Twelve common bean genotypes were used (Apore, H-4-7, PF-9029975, CI-128, Carioca MG, CI-21, Carioca 300V, Ouro Negro, A-285 Ruda, ESAL 693, Perola e IAC Carioca Arua), and evaluated in four seasons (Jul-Nov/97, Nov/97-Feb/98, Feb-Jun/98 and Jul-Nov/98), based on ten morpho-agronomic traits. A randomized block design with three replications was utilized. The multivariate techniques showed similar results mainly for identifing the more divergent genotypes. Among them, ESAL 693 and Ouro Negro were genetically different between themselves and among the other genotypes. PF-9029975 and Carioca MG were genetically similar, although different of other genotypes according to average Euclidean procedures. It should be pointed out that Apore genotype was divergent of Perola genotype, although the last one is a selected line in the Apore. Therefore, all of those genetically divergent genotypes are promissing to cross for obtaining higher segregating populations, specially ESAL 693 with the others that have a carioca grain type. A resonable correspondence was found in the identification of traits with smallest contribution to genetic diversity.

Divergência genética entre acessos de açaizeiro fundamentada em descritores morfoagronômicos

The objective of this research was to estimate the genetic divergence among accessions of the assai palm, sampled in the germplasm collection of Embrapa Amazonia Oriental based on morphoagronomic traits, at Belem, PA. The 22 morphoagronomic traits were evaluated in 87 accessions, from 1995 to 2001. Among the 22 traits, seven were relative to the plant, three to the flowering, three to the fruit, and nine to the fruit production. The traits were analyzed using univariate and multivariate analysis. The estimates of the dissimilarities were obtained by the average Euclidian distance with standardized data, and the groupings by UPGMA and Tocher methods. The accessions presented high variation index in the majority of the characters. Genetic distances among accession pair varied from 0.09 to 1.87, with average of 1.39. The method UPGMA divided the accessions into five groups, while the Tocher method formed 24 groupings. The five accessions indicated as more divergent must be used in breeding programs aiming at the obtention of superior genotypes.

Genetics of common bean resistance to white mold

ABSTRACT - The objective of the research was to investigate the nature and magnitude of the genetic factors involved in theresistance of the common bean to white mold. The lines G122 (resistant) and M20 (susceptible) were crossed to yield F 1 and F 2 generations and F 2:3 progenies. The experiment was set up using the random block design with two replications, each of which wasevaluated twice with fungal inoculations being performed on 28 and 38 day-old plants using the straw test method. Six to eight daysafter inoculation evaluations were conducted on individual plants and at the level of means of progenies using a diagrammatic scaleranging from 1 to 9. The additive-dominance model adopted was efficient, and the genetic control of resistance was predominantlydue additive effects. Estimates of broad-sense heritability indicated that selection would be more efficient when based on the meansof progenies and when successive inoculations are employed.Key words: Sclerotinia sclerotiorum ; Phaseolus vulgaris ; genetic parameters .

Identification of resistant genotypes considering polygenic systems in host-pathogen interaction

A resistencia de plantas a patogenos e a forma mais viavel de controle de doencas. No entanto, a identificacao de genotipos resistentes muitas vezes e dificil, principalmente pelo desconhecimento da relacao patogeno-hospedeiro. O objetivo desse trabalho foi testar uma metodologia que conseguisse, de maneira simples, informar sobre a resistencia vertical e horizontal dos hospedeiros e tambem sobre a agressividade e virulencia dos patogenos. Para isso foi realizada uma simulacao utilizando vinte, dez e cinco racas do patogeno e vinte hospedeiros. A reacao do hospedeiro era controlada por 10 genes com 2 alelos cada. Desses genes, 8 eram de pequeno efeito, 1 de medio e 1 de grande. No patogeno o controle genetico era identico ao hospedeiro. Foi considerada na simulacao apenas a presenca de locos em homozigose, com ausencia de epistasia. A simulacao baseou-se na severidade de doenca esperada com a inoculacao dos vinte hospedeiros com as vinte racas do patogeno, segundo os modelos aditivo e interativo (com modificacoes) propostos por Parlevliet e Zadoks (Euphytica 26: 5-21, 1977). A analise dos dados foi atraves do modelo IV de Griffing (1956), utilizando o esquema de dialelo parcial. Encontrou-se uma alta correlacao entre capacidade geral de reacao (GRA) e a resistencia horizontal, e tambem alta correlacao entre capacidade geral de agressividade (GAA) e a patogenicidade potencial da raca, mostrando ser indicador da agressividade. A capacidade especifica de interacao (SIA) revelou-se um indicador da resistencia vertical do hospedeiro e da virulencia do patogeno. A simulacao com numero menor de racas (10 e 5) mostrou resultados similares aos obtidos com as 20. Tanto no modelo interativo quanto no aditivo a SIA mostrou-se significativa, indicando ser possivel a existencia da interacao patogeno com hospedeiro nos dois modelos.