Ângela de Fátima Barbosa Abreu

Phenotypic recurrent selection in the common bean (Phaseolus vulgaris L) with carioca-type grains for resistance to the fungi Phaeoisariopsis griseola

The efficiency of recurrent selection was assessed in obtaining common bean (Phaseolus vulgaris L) plant lines resistant to the phytopathogenic fungi Phaeoisariopsis griseola. The base bean population was obtained from the partial diallel between seven lines with carioca-type grains and 10 sources of resistance to P. griseola. The plants most resistant to the pathogen were selected in the F2 (S0) generation of the populations (C-0). The best S0:1 plants that presented carioca-type grains were intercrossed to obtain cycle I (C-I). The same procedure was adopted to obtain cycles C-II to C-V. In each recurrent selection cycle, S0:1 progenies selected were also assessed in experiments carried out in Lavras, Brazil, always using as check the Carioca MG (susceptible to P. griseola) and Perola (tolerant) cultivars. The response to selection for resistance to the pathogen was estimated from the general mean of the S0:1 progenies from each selective cycle compared to the susceptible check Carioca MG. The estimated gain was 6.4% per cycle and the indirect response in grain yield by selection for resistance to the pathogen was 8.9% per cycle. The variability detected among the progenies in the last selective cycles enabled the prediction of additional responses to recurrent selection.

Seleção recorrente para três caracteres do feijoeiro

The objective of this study was to estimate the genetic progress after three recurrent selection cycles in common bean. The progenies in each cycle were evaluated over three generations S0:1, S0:2 and S0:3 on the experimental field of the Department of Biology at the Federal University of Lavras (UFLA), in Lavras, Minas Gerais, from 2001 to 2006. In the experiments, grain yield, grain type and plant architecture were evaluated. Analyses of variance and the estimates of genetic and phenotypic parameters were obtained in all progeny evaluations. The progress per trait was estimated and, upon standardization of variables, the progress for the three traits simultaneously. Since the cycles refer to different years, the performance of two lines that participated in all evaluations was used as base to lessen the environmental effect in the estimates. The difference between the bs of the linear regression, of the number of cycles, the independent variable (x), and the mean performance of the trait under selection, the dependent variable (y), of the progenies and of the controls, provided the estimate of the genetic progress. Considering the three traits simultaneously after three recurrent selection cycles the genetic progress was 3.1% per cycle,. The existence of genetic variability in the progenies suggests the possibility of continuous success with selection.

Selection potential for seed yield from intra- and inter-racial populations in common bean

Common bean populations from crosses between lines of different races are thought to be more promising for selection of high yield potential than those from intra-racial crosses. Three distinct diallel crosses were made to test this hypothesis and to determine the possibility of substituting diallel crosses for multivariate techniques that estimate genetic divergence. The crosses were between races Mesoamerica × Mesoamerica, Mesoamerica × Durango and Jalisco, and Mesoamerica × Nueva Granada. The parents and the resulting F4 populations were evaluated at Lavras-MG, Lambari-MG and Patos de Minas-MG, Brazil. The diallel analysis of seed yield was done and the genetic divergence estimated by Mahalanobis distance. Estimates of general and specific combining ability indicated that some inter-racial populations were more promising for selection to increase seed yield than intra-racial populations. However, due to their undesirable seed color and size, and growth habit, especially in a short term breeding program, the chances of obtaining high yielding lines with an acceptable bean is reduced. Genetic divergence was not a good measure to choose the parents because usually, the most divergent groups included were not adapted lines.

Resposta diferencial de linhagens de feijoeiro ao nitrogênio

It was evaluated 100 breeding lines of common bean in the presence and absence of N in cover in four conditions aiming at identifing the lines of beans which would be tolerant to nitrogen (N) stress and/or also responsive to this nutrient. In each condition there were two distinct experiments with and without N, in a 10 x 10 triple lattice design, being the plot constituted by a line with three meters of length. It was estimated the index of efficiency of nitrogen utilization, through the average grains yield. The obtained yield with N was 12% above the one without N, in the average of the four conditions. By decomposing the effect of levels for each line, in 77% of them there was no answer to the nitrogen fertilization in cover. This, only 22 lines positively responded to nitrogen fertilization and among them the efficiency of N utilization ranged from 11.3 to 18.3kg of grains per kg of applied N.

Trinta e dois anos do programa de melhoramento do feijoeiro comum em Minas Gerais

Conduziu-se este trabalho, com o objetivo de proceder a analise critica do Programa de melhoramento genetico do feijoeiro comum em Minas Gerais nos ultimos 32 anos com enfase nas implicacoes da interacao linhagens x ambientes, alem de avaliar se houve progresso genetico. Para isso, foram utilizados dados de 169 experimentos conduzidos no periodo de 1974 a 2004 e que envolveram 16 locais e tres safras. A media da cultivar Carioca, comum em todos os experimentos, foi utilizada como estimador do efeito ambiental e a media das cinco melhores linhagens sob avaliacao de cada bienio, como efeito fenotipico. A diferenca entre essas duas medias forneceu o desvio genetico. O coeficiente de regressao linear entre desvio genetico Y (variavel dependente) e o bienio X (variavel independente) forneceu a estimativa do progresso genetico. As interacoes linhagens x safras e linhagens x anos foram, na maioria dos casos, significativas, contudo, suas contribuicoes para a variacao total foram inferiores a de linhagens x locais. Desse modo, fica clara a necessidade de que os experimentos sejam conduzidos em um maior numero de locais. O programa de melhoramento genetico do feijoeiro da UFLA tem sido eficiente e tem obtido linhagens com menor risco de adocao.

Genetic control of plant architecture in the common bean (Phaseolus vulgaris L.)

More erect plant architecture has been a goal in the development of bean cultivars. Aiming to obtain more information about genetic control of traits related to plant architecture, this work was carried out between August 1995 and July 1997 in the southern and Alto Sao Francisco regions, in the State of Minas Gerais, Brazil. Initially, analyses were performed with individual plants of parents and different segregant generations from the crosses Carioca-MG x H-4 and Carioca x FT-Taruma. In these experiments, besides degree of erectness, other traits were evaluated: ramification degree, internode length, internode diameter and height of insertion of the first pod. Mean and variance components and heritability at an individual level were estimated. Later, families derived from F2 or F3 plants of the same crosses were evaluated for degree of erectness. Genetic and phenotypic variance between family averages, heritabilities using variance components, and realized heritability were estimated. Of the morphological traits, internode length varied the most. There was a predominance of additive effect in the control of this trait. Evaluating plant architecture with individual plants for degree of erectness was not efficient. However, when families were used, genetic parameter estimates confirmed the possibility of successful selection, especially if evaluated for a few generations and/or environments, despite the strong environmental influence on trait expression.

Seleção recorrente fenotípica para florescimento precoce de feijoeiro 'Carioca'

O objetivo deste trabalho foi avaliar a eficiencia da selecao recorrente fenotipica em relacao ao numero de dias para o inicio do florescimento em feijoeiro e verificar se a selecao afeta outros caracteres. Utilizou-se uma populacao proveniente da mistura das populacoes F2 (S0) de 11 combinacoes hibridas, avaliadas para a precocidade. As plantas S0 (ciclo 0), que floresceram mais precocemente, foram intercruzadas para a obtencao do ciclo I. As sementes obtidas foram utilizadas para a continuidade da selecao, e o processo foi repetido ate o quinto ciclo seletivo. O progresso genetico foi avaliado com cinquenta e tres progenies, provenientes da mistura das sementes das plantas S0 apos uma autofecundacao (S1:2) de cada ciclo. Os caracteres avaliados foram: numero de dias para o florescimento, severidade da mancha-angular (Phaeoisariopsis griseola), numero de dias para a maturacao, produtividade e tipo de graos. Constatou-se que o progresso com a selecao foi de 2,2% ao ano, o que indica que a selecao recorrente fenotipica foi efetiva em reduzir o numero de dias para o florescimento. Nao houve resposta correlacionada a selecao quanto ao numero de dias para o florescimento nos demais caracteres avaliados, do que se depreende ser possivel a selecao de progenies que associem florescimento precoce a expressao fenotipica dos demais caracteres, conforme o interesse dos melhoristas.

Eight cycles of recurrent selection for resistance to angular leaf spot in common bean

The genetic progress (GP) was evaluated after eight cycles of recurrent selection for resistance to angular leaf spot in common bean and indirect gain for yield and grain type. The base population (Cycle-0) was obtained from the diallel cross of seven lines with carioca grain and ten resistance sources. To obtain Cycle I, the most resistant S0 plants of Cycle 0 were intercrossed. The same procedure was adopted in the subsequent cycles. GP for resistance to the pathogen was estimated by the overall average of the progenies of each cycle in comparison with control Carioca MG and for productivity in comparison to the controls Carioca MG and Perola. Lines of the first six cycles were used for grain type. No GP was detected for resistance to angular leaf spot. However, the indirect yield gain was 2.3% and 2.5% in the selection for grain type, with values similar to those obtained by direct selection for these traits.

Associação entre arquitetura de planta e produtividade de grãos em progênies de feijoeiro de porte ereto e prostrado

The objective of this work was to evaluate if progenies with erect and prostrate plant habit, from the same genetic pool, have the same yield potential. Crosses between a prostrate and three erect cultivars were made yielding three populations up to the F5 generation. In this generation, erect and prostrate plants from each population were selected and evaluated in separate experiments. Generations F5:6 F5:7 and F5:8 were evaluated for plant architecture, in a scale from 1 (erect) to 9 (prostrate) and for grain yield. The expected gain for selection for plant habit and the correlated response in grain yield, as well as gain from selection for grain yield with the correlated response in plant habit were estimated. The correlation between selection for better plant habit and grain yield was low and negative. It is possible to select common bean progenies simultaneously for yield and plant habit.

Variabilidade genética associada à germinação e vigor de sementes de linhagens de feijoeiro comum

The objective of this study was to estimate the genetic variability for characters related with the germination rate and the capacity of the plants to occupy the ground quickly. Ninety four lines from the common bean (Phaseolus vulgaris L.) germoplasm from the Universidade Federal de Lavras, differing in several characters as color, size and shape of the seeds were used. Two experiments were carried out to evaluate the bean lines. The first was conducted at 120 days and the second 360 days after the beginning of storage (room temperature and humidity and under low light). Percentage of germination (%G), emergency speed rate (ESR) and dry matter (DM) were obtained. The variables were standardized and obtained the sum of the ESR + DM. Phenotypic, genetic and environmental correlations between all the characters were obtained and the expected gain was estimated with the selection and correlated response. Both the G% and ESR presented reduced levels in the evaluation at 360 days after seed storage in comparison with the evaluation at 120 days. It was possible to obtain the gain with the selection, for higher %G, ESR and DM. The higher gain was obtained in the first experiment. Among the lines evaluated, there are genetic sufficient variability to proceed the selection for germination and emergence. The lines JALO EEP 558, PI-103 and CVII 39-24 were identified as the best for germination and emergence and the lines RP-2, BP-34 and ESAL 569 were those with smaller vigor.