Magno Antonio Patto Ramalho

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.

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.

Combining ability of elite clones of Eucalyptus grandis and Eucalyptus urophylla with Eucalyptus globulus

In Brazil, eucalyptus breeding programs for cellulose production has used two species, Eucalyptus grandis and Eucalyptus urophylla. Nevertheless, it would be useful to introgress alleles from other species to improve wood quality and volume. The objective of this research was to evaluate the hybrid potential of elite clones of E. grandis and E. urophylla from the Aracruz Celulose Company S. A. with Eucalyptus globulus clones. To do so, six elite clones were crossed with ten E. globulus clones in a half-diallel mating design. The resulting hybrid combinations as well as the four check clones were evaluated in randomized complete block experiments with single plant plots and 40 replicates from September to October 2001 at three Brazilian sites, Aracruz and Sao Mateus in the Espirito Santo state and Caravelas in Bahia State. Two years later the circumference at breast height (CBH) and the wood density (WD) were measured. The means were submitted to diallel analysis according to the Griffing method (1956), adapted by Geraldi and Miranda Filho (1988). Although the number of clones involved was small, the crossings of elite clones of E. grandis and E. urophylla with clones of E. globulus were promising, especially for wood quality gains.

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.

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.

Chemical composition as related to seed color of common bean

This study aimed to quantify the levels of protein and minerals in common bean lines from the Germplasm Bank of Universidade Federal de Lavras and to investigate the relationship between color and the mineral and protein contents of the beans. One hundred common bean lines with carioca, black and other grain color patterns were assessed for the protein levels and the mineral contents of phosphorus, potassium, calcium, magnesium, copper, manganese, zinc, and iron. Genetic variability was detected among the different groups and also between lines within each group. In general, the protein, iron and zinc contents were highest in the black bean lines. The carioca grain was outstanding for manganese and magnesium and the other grain colors for calcium. Positive correlations between most nutrients were observed. This indicates the possibility of obtaining lines with higher nutritional value by selection.