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White mold caused by Sclerotinia sclerotiorum is an important disease that may lead to severe crop losses. The resistance of common bean (Phaseolus vulgaris) to white mold is quantitative and affected by environmental conditions. In this case, QTL identification of higher effect and stable in several populations and environments (Meta-QTL) can be useful in marker-assisted breeding. This study aimed to analyze the expression of candidate genes within Meta-QTL regions in two common bean lines Cornell 605 (resistant) and Beryl (susceptible), inoculated with S. sclerotiorum, at different evaluation times. We did so by conducting a phenotypic analysis of the reaction lines were evaluated at 3, 7 and 11 days after inoculation (DAI), with the aim of verifying the reaction discrepancy between the lines in the test environment, and assessing the the expressions of seven genes (PvPKF, PvF-Box, PvERF1, PvPGIP4, PvPR1, PvPOD and PvMYB) within Meta-QTL intervals were analyzed in the lines, at 0, 24, 48 and 72 h after inoculation (HAI). The phenotypic evaluation showed high susceptibility in Beryl and suggested that most of the interaction between lines and evaluation times occurred due to the rapid development of symptoms in the susceptible line. Based on RT-qPCR results, the genes PvPKF and PvPOD were the most promising to explain partial Cornell 605 resistance conditioning. Differences in the genetic backgrounds of the lines used in this study and the fact that the evaluations were performed in a greenhouse may help to explain why the other candidate genes were not highly expressed in Cornell 605.

White mold, caused by the fungus Sclerotinia sclerotiorum (Lib.) de Bary is currently one of the major diseases affecting bean cultivars, especially in irrigated crops, and extremely difficult to control. Genetic improvement in the form of more resistant lines has been sought for inclusion in the integrated management of this disease. When selecting resistant genotypes, an efficient, fast and simple evaluation method regarding plant reactions to the pathogen is required. In this context, the aim of the present study was to compare straw and seedling phenotyping methods in the evaluation of disease progression by nonlinear models and evaluate the interaction of the phenotyping method with genotype resistance and evaluation timeframes. The results indicate that both phenotyping methods are well correlated regarding bean resistance groups. The applied methods lead to distinct inferences on genotype resistance, and disease progress is closely linked to the resistance level of the evaluated genotype. Both phenotyping methods are efficient, but in different situations. The symptom progression models display similar adjustments to the symptom levels of both methods.

In many species, low levels of polymorphism prevent the assembly of linkage maps that are used to identify genetic markers related to the expression of quantitative trait loci (QTLs). This study compared two methods of locating QTLs in association studies that do not require a previous estimation of linkage maps. Method I (MI) was a Bayesian multiple marker regression and Method II (MII) combined multiple QTL mapping and "moving away from markers". In this method, markers are not directly regressed to the phenotype, but are used as pivots to search for QTLs along the genome. To compare methods, we simulated 300 individuals from an F2 progeny with two levels of marker loss (20 and 80%). A total of 165 markers and seven QTLs were spread along 11 chromosomes (roughly emulating the genetic structure of the common bean, Phaseolus vulgaris). A real data example with 186 progenies of a F2:4 generation of the species was analyzed using 59 markers (17 simple sequence repeats, 31 amplified fragment length polymorphisms, and 11 sequence-related amplified polymorphisms). MII was more precise than MI for both levels of marker loss. For real data, MII detected 17 candidate positions for QTLs, whereas MI did not detect any. MII is a powerful method that requires further studies with actual data and other designs such as crossover, and genome-wide studies.

Genetic diversity is an essential factor for the success of any plant breeding program and should be considered to ensure genetic gain through breeding. In Brazil, research on the genetic diversity and population structure of soybean is required since the species is an important commodity of the country. The study addressed the genetic diversity and population structure of 77 soybean genotypes using 35 SSR markers. The estimate of the diversity index showed that the level of genetic diversity in the soybean collection is low. Similarly, the Jaccard coefficient and Bayesian model based on clustering analysis confirmed the low diversity among soybean genotypes, providing evidence for the assumption of a genetic bottleneck effect on Brazilian soybean genotypes. The results also reinforced the importance of finding and incorporating new genetic resources of soybean in the genetic pool of Brazilian soybean to warrant genetic gain in soybean breeding in the future.

The aim of this study was to investigate changes in defence compounds of common bean cultivars with different levels of resistance to the fungus Sclerotinia sclerotiorum and determine the relation of the compounds to pathogen tolerance. The lines were inoculated with the pathogen and assessed for enzymatic and non-enzymatic parameters related to plant defence: peroxidases (POX), polyphenol oxidases (PPO), catalase (CAT), superoxide dismutase (SOD) and ascorbate peroxidase (APX), total soluble phenol and lignin contents. Stem tissue samples were collected from two regions of the plant for biochemical analyses. Stem tissue samples were collected from two regions of the plant for biochemical analyses. In the position one, 5 cm of the stem was collected from the region with necrosis caused by the pathogen, and in the position two, 5 cm of the stem was collected from the end of the position one at the times of 12, 24, 48, 72, 96 and 120 h after inoculation (HAI). Greater lignin and total soluble phenol contents and greater induction of POX and SOD activity in inoculated plants in the region near the inoculation (position one) indicate local activation with later signalling for activation of defence mechanisms in other regions of the plant. The genotype with a greater level of resistance was superior to the susceptible one in regard to lignin production and the activities of POX, APX and SOD defence enzymes. These results suggest that a combination of these defence responses in common bean may contribute to greater plant resistance to the pathogen and that these enzymes have potential use in selection of common bean genotypes.

White mold, caused by Sclerotinea sclerotiorum (Lib.) de Bary is one of the most important diseases of the common bean (Phaseolus vulgaris L.) worldwide. Physiological resistance and traits related to disease avoidance such as architecture contribute to field resistance. The aim of this study was to verify the efficiency of recurrent selection in physiological resistance to white mold, “Carioca” grain type and upright habit in common bean. Thirteen common bean lines with partial resistance to white mold were intercrossed by means of a circulant diallel table, and seven recurrent selection cycles were obtained. Of these cycles, progenies of the S0:1, S0:2 and S0:3 generations of cycles III, IV, V and VI were evaluated. The best (8 to 10) progenies of the seven cycles were also evaluated, in two experiments, one in the greenhouse and one in the field. Lattice and/or randomized block experimental designs were used. The traits evaluated were: resistance to white mold by the straw test method, growth habit and grain type. The most resistant progenies were selected based on the average score of resistance to white mold. Subsequently, they were evaluated with regard to grain type and growth habit. Recurrent selection allowed for genetic progress of about 11 % per year for white mold resistance and about 15 % per year for the plant architecture. There was no gain among cycles for grain type. Progeny selection and recurrent selection were efficient for obtaining progenies with a high level of resistance to white mold with “Carioca” grain type and upright habit.

We aimed to identify simple sequence repeat (SSR) markers linked to quantitative trait loci (QTLs) associated with white mold resistance in a segregating population derived from a cross between common bean cultivars Jalo and Small White, in the Southern State of Minas Gerais. Parents were crossed to obtain the F2 generation of 190 plants. From these, F2:3 and F2:4 progenies were obtained for phenotypic evaluation. DNA was extracted from F2 plants and parents for genotyping with SSR primers. For phenotypic assessment by the straw test, we used 190 F2:3 progenies and six lines in a triple-lattice design of 14 x 14 m. Nine trials were conducted for phenotyping by the oxalic acid method to evaluate 177 F2:4 progenies, in addition to the two parents and two common treatments represented by the Jalo and Corujinha lines. The experimental design for the oxalic acid method was completely randomized with three replicates. Adjusted means of evaluations related to F2:3 and F2:4 were used to identify QTLs by using the moving away method from the marker under Bayesian analysis. The markers GATS91, BM197, and X60000 stood out with high heritability and with effects on disease reduction by the straw test; therefore, these markers are promising for selection. The markers BM183, BM189, and SSR-IAC143 were associated with the QTLs identified by oxalic acid, providing greater effects in white mold resistance with high heritability. Based on the oxalic acid and straw test methods, the most prominent marker was PVBR189.

The interaction between polygalacturonase-inhibiting proteins (PGIPs), produced by plants, and endopolygalacturonases (PGs), produced by fungi, limits the destructive potential of PGs and can trigger plant defense responses. This study aimed to i) investigate variation in the expression of different common bean (Phaseolus vulgaris L.) genotypes and its relationship with resistance to white mold (Sclerotinia sclerotiorum); ii) determine the expression levels of PvPGIP genes at different time points after inoculation with white mold; and iii) investigate differences in PvPGIP gene expression between two white mold isolates with different levels of aggressiveness. Four bean lines were analyzed, including two lines from a recurrent selection for white mold (50/5 and 84/6), one resistant line that was not adapted to Brazilian conditions (Cornell 605), and one susceptible line (Corujinha). Gene expression was investigated at 0, 1, 2, 3, and 5 days after inoculation. The isolate UFLA 03 caused no significant difference in the relative expression of any gene examined, and was inefficient in discriminating among the genotypes. For the isolate UFLA 116, all of the genes were differentially expressed, as they were associated with resistance to white mold, and the expressions increased until the third day after inoculation. The 50/5 line was not significantly different from the Corujinha line for all of the genes analyzed. However, this line had a resistance level that was similar to that of Cornell 605, according to the straw test. Therefore, the incorporation of PvPGIP genes can increase the resistance of lines derived from recurrent selection.

The analysis of multiples traits has been largely employed in animal and forestry crop breeding; however, in annual crops such as common bean this approach is practically lacking. This study examined the selective accuracy and estimates of genetic parameters in common bean using single- and multi-trait analyses in several designs of genetic correlations and heritabilities by means of simulated- and real-traits. We also compared the efficiency of the Bayesian and REML methods as regarding its selective accuracy and estimates of genetic parameters. In real data experiments, 100 endogamic families of common bean were assessed for grain yield (GY) and grain type (GT) in three environments using a 10 × 10 triple lattice design. Single- and multi-trait analyses were applied for these traits using REML-based BLUP analysis and Bayesian methods. In simulated experiments, traits corresponding to GY and yield components in common bean were simulated under several levels of genetic correlations and evaluated under different levels of heritability in order to verify in which genetic/experimental design it is advantageous to apply single- or multi-trait analyses. The results obtained in this study indicated that GY and GT present low genetic correlation and, therefore, multi-trait analysis may be unjustifiable for these traits. The Bayesian and REML multi-trait analyses were equivalent in point and interval estimates of genetic parameters and predictive accuracy, both for the field and simulated experiments. In addition, it was found that multi-trait analysis is justified in situations where the traits present low/moderate heritability and medium/high genetic correlations among them. It also was found that GY in common bean may be outstandingly favored in accuracy when evaluated jointly with its components. Thus, one can conclude that the simultaneous analysis of GY and yield components in common bean may provide superior gains accuracy and selection efficiency, being the response to selection better obtained by use of the multi-trait heritability.

This study aimed to determine the minimum number of plants per plot to assess the field resistance in common beanto white mold. Thirteen cultivars were inoculated with six isolates of Sclerotinia sclerotiorum and evaluated in a randomized blockdesign with three replications and plots consisting of 1-m rows with 15 plants. Plants were inoculated by the straw test as proposedby Petzoldt and Dickson (1996), to evaluate partial resistance in a greenhouse. Eight days after inoculation the disease severity wasevaluated on a 1-9 diagrammatic scale, where 1 = asymptomatic plants to 9 = plant death. To determine the minimum number ofplants per plot, the following methods were used: maximum curvature, segmented linear model, quadratic segmented model and therelative CV model. There were significant differences among cultivars and isolates and no significant cultivar - isolate interaction.It was observed that eight plants per plot is an adequate number to assess the reaction of common bean to white mold.

Vegetative propagation of potato allows the dissemination of viruses that can cause drastic drops in tuber yield. Potato virus Y (PVY) is one of the most important viruses of potato due to the non-persistent mode of transmission through vector insects. Genetic resistance is the recommended control measure since the chemical control of vector insects is not effective. This study aimed to identify PVY-immune clones through potato grafting onto virus-infected tobacco plants, check their genetic constitution for the Ry allele through PCR and evaluate the clones' field performance. Sixty-two clones were identified as PVY-immune through grafting. The SCAR marker allowed the identification of two duplex clones for the Ry allele (RyRyryry), which can be used as parents to originate progenies with about 80% PVY-immunity in crossings with susceptible clones. Besides, the clones were productive and presented high tuber dry matter content.

The effect of natural selection on microsatellite simple sequence repeat (SSR) alleles was investigated in two distinct common bean (Phaseolus vulgaris) generations (F8 and F24) derived from the cross between the P. vulgaris cultivars Carioca MG x ESAL 686. The F2 segregant population was propagated by the bulk method and 107 plants were sampled in two generations (F8 and F24). Each plant generated one family which was replicated by the bulk method to F8:11 and F24:27 families from which DNA was extracted. Thirty pairs of microsatellite primers were polymorphic for the parents and the bulk of the F24:27 families. Out of 30 loci selected by natural selection, 29 microsatellite alleles came from the Carioca MG parent and one allele came from the ESAL 686 parent. Natural selection affected all the generations and its intensity was specific for each locus and generation. Therefore all the alleles selected at each locus must be important for adaptation in a breeding program.

Objective of the present study was to select common bean lines wit the traits anthracnose and angular leaf spot- resistance, high yield, Carioca type grains and an upright plant type. One hundred and fifty-three lines were selected from five segregating families derived from backcrosses using G2333 (donor parent) and the lines ESAL 696 and CI 140 (recurrent parents). The lines were evaluated and selected in three seasons under inoculation with the races 2047, 1545 and 81 of C. lindemuthianum and also tested with the SCAR marker of allele Co-5. Lines with high grain yield, Carioca type grains, upright plant type, and anthracnose- resistance were selected. The SCAR marker was not effective for the selection of resistant lines with Co-5 allele. No angular leaf spot- resistant lines were identified.

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. Made available in DSpace on 2022-05-15T05:10:34Z (GMT). No. of bitstreams: 1 euphytica-2005.pdf: 807386 bytes, checksum: 9615d3ae20925b5d30ea7c91310c9fb4 (MD5) Previous issue date: 2005

RAPD markers were used to assess the potential five inbreeding methods have to release genetic variability. These methods were employed until family selection in the F 5 generation, plus the parents Carioca and Flor de Mayo, and the test cultivar Perola. DNA was extracted from 16 plants per family for RAPD reaction. Twenty-two primers amplified DNA fragments linked to a number of grain yield loci, weight of 100 seeds, number of days to flowering, and reaction to the oidium and angular leaf spot. To estimate genetic similarities between every genotype pair in each inbreeding method 42 polymorphic bands amplified among the families and parents were used. Genetic similarities were UPGMA-clustered and grouped by multidimensional scaling. The bulk method was most efficient to release genetic variability, followed by bulk in F 2 families, SSD, bulk in F3 families, and pedigree. The bulk method created families with higher similarities close to the Carioca, which is one of the regionally most grown cultivars.

The objective of this study was to identify RAPD and SSR markers associated with a resistant allele for angular leaf spot (Phaeoisariopsis griseola) from the line 'ESAL 550', derived from the Andean 'Jalo EEP 558' cultivar, to assist selection of resistant genotypes. The resistant line 'ESAL 550' and the susceptible cultivar 'Carioca MG' were crossed to generate F1 and F2 populations. One hundred and twenty F2:3 families were evaluated. The DNA of the 12 most resistant families was bulked and the same was done with the DNA of the 10 most susceptible, generating two contrasting bulks. One RAPD and one SSR marker was found to be linked in coupling phase to the resistant allele. The SSR marker was amplified by the primer PV-atct001(282C), and its distance from the resistant allele was 7.6 cM. This is the most useful marker for indirect selection of resistant plants in segregating populations. The RAPD marker was amplified by the primer OPP07(857C) linked in coupling phase to the resistant allele, and distant 24.4 cM. Therefore, this RAPD marker is not so useful in assisting selection because it is too far from the resistant allele.

The Carioca MG (susceptible = P 1 ) and Perola (resistant = P 2 ) cultivars were used as parents in a cross aiming at investigating the genetic control of the common bean plant reaction to Phaeoisariopsis griseola. Two hundred and fifty-one families (141 F 2:3 , 53 F 2 RC 11 and 57 RC 12 ) from this cross were evaluated for angular leaf spot severity in the leaves and pods, in two generations, under natural incidence of the pathogen. The genetic variance components, heritability in the broad ( 2 h ) and narrow ( 2 h ) senses and number of genes that control the reaction to angular leaf spot were estimated. The families were genetically different for level of resistance to the pathogen, and varied from 59.20% to 72.41% and varied from 19.32% to 73.79% for the leaf analysis. For reaction to the pathogen in the pods, the varied from 55.00% to 68.22% and was nil, indicating the presence of dominant alleles in the control of the trait, and of genes different from those responsible for the control of the disease in the leaves. Only one gene was estimated for the genetic control of the reaction to the pathogen in the leaves and two genes in the pods.

The objectives were: 1 - to identify, under different environments, RAPD markers linked to loci that control the 100 seed weight of common beans; 2 - to evaluate the existence of interactions involving QTLs with planting dates and locations; 3 - to compare detection procedures of markers linked to QTLs utilizing the methods of mapping and multiple regression. One hundred and ninety-six recombinant inbred lines derived from the cross of cultivars Carioca x Flor de Mayo were evaluated under two traditional sowing dates for common beans in 1996, 1997 and 1998, in Lavras and Patos de Minas, Brazil. For the phenotypic evaluation of the families, seven field experiments were conducted. The experimental design used was a 14 x 14 partially balanced Square Simple Lattice. Results indicated that interaction of QTLs by location were significant, and some stable QTLs were identified. Multiple regression analysis identified a greater number of QTL-linked markers than the process of composite interval mapping. There was no coincidence between results obtained with the two methods studied. Molecular markers which were considered of greater potential use on marker- assisted selection for seed weight were OPN-02 (1445 pb) e OPM-06 (1096 pb).

This study was realized with the objective of verifying the resistance to white mold of common bean progenies derived from recurrent selection for resistance to angular leaf spot. The plant material used was obtained from a program of recurrent selection, which was started by crossing seven lines with carioca grain type with ten sources of resistance to angular leaf spot according to the partial diallel scheme. To evaluate the resistance to white mold, it was verified the reaction of 17 parents plus 35 selected progenies, to oxalic acid. Huge heterogeneity among the parents was observed, showing that some of them have resistance alleles to white mold, and thus, there is a possibility of recombine these alleles through the recurrent selection and obtaining progenies with high levels of resistance. Even in initial cycles, some progenies exhibited resistance to white mold similar to the one of cultivar 'G-122', which presents good level of resistance to this disease. This leads to infer that the original population already had some level of physiological resistance for the reaction to absorption of oxalic acid, and also for resistance to angular leaf spot. Thus, among the selected progenies for resistance to angular leaf spot, grain type and high yield, at least four progenies have resistance to white mold similar to the source of resistance 'G-122'. Este estudo foi realizado com o objetivo de verificar a resistência ao mofo branco de progênies de feijão, provenientes de seleção recorrente para resistência à mancha angular. O material vegetal utilizado foi obtido de um programa de seleção recorrente, iniciado com o intercruzamento entre sete linhagens com grãos tipo carioca e dez fontes de resistência à mancha angular no esquema dialelo parcial. Para avaliação da resistência ao mofo branco, foi verificada a reação desses 17 genitores mais as 35 progênies obtidas, ao ácido oxálico. Foi observada uma ampla variabilidade nos genitores, indicando que alguns possuem alelos de resistência ao mofo branco e, assim, há possibilidade de associação desses alelos no programa de seleção recorrente e obtenção de progênies com níveis superiores de resistência. As progênies que se apresentaram como mais resistentes foram MAV-1.7, MAV-3.36, MAVI-21 e MAVI-60. Mesmo em ciclos iniciais, algumas progênies apresentaram nota média de reação ao mofo branco semelhante à da cultivar 'G-122', que apresenta bom nível de resistência a essa doença. Isso leva a inferir que a população original utilizada já possuía algum nível de resistência fisiológica para a reação à absorção ao ácido oxálico e também para a resistência à mancha angular. Assim, entre as progênies selecionadas para a resistência à mancha angular, tipo de grão e produtividade, pelo menos quatro apresentam nível de resistência ao mofo branco semelhante à fonte de resistência 'G-122'.

The aim of this study was to use multiple DNA markers for detection of QTLs related to resistance to white mold in an F2population of common bean evaluated by the straw test method. The DNA from 186 F2plants and from the parents was extracted for genotypic evaluation using SSR, AFLP, and SRAP markers. For phenotypic analysis, 186 F2:4progenies and ten lines were evaluated, in a 14 × 14 triple lattice experimental design. The adjusted mean values of the F2:4progenies were used for identification of QTLs by Bayesian shrinkage analysis. Significant differences were observed among the progenies for reaction to white mold. In identification of QTLs, 17 markers identified QTLs for resistance—13 SSRs and 4 AFLPs. Themoving awaymethod under the Bayesian approach proved to be efficient in the identification of QTLs when a genetic map is not used due to the low density of markers. The ME1 and BM211 markers are near the QTLs, with the effect of increasing resistance to white mold, and they have high heritability. They are thus promising for marker-assisted selection.

Aiming at using RAPD markers to accelerate the recovery of desirable phenotypes in backcross programs, 167 common bean plants belonging to BC 1 , BC 2 and BC 3 resistant to the 2047 race of the fungus Colletotrichum lindemuthianum were selected after inoculation. The DNA of those plants and of the parents G2333 (donor), ESAL696 and CI140 (recurrents) was extracted and 70 polymorphic bands were obtained using 34 primers, through the RAPD procedure. Genetic similarities between BC plants and parents for each group were estimated. It was verified that RAPD was efficient in estimating genetic diversity among genotypes, as well as parentage for the BC 1 F 4 and BC 2 F 1 populations in relation to their parents, according to their genealogy. The efficiency of the genetic similarity for determining the parentage of the backcross populations in relation to their parents confirms its usefulness in selecting plants more similar to the recurrent parent, even in BC 1 .

Aiming at verifying whether the common bean allele of resistance to Erysiphe polygoni is associated with undesirable agronomic characters and identifying RAPD markers linked to the resistance allele of the line ESAL 686, the reaction of 64 F 1:2 families of the backcross (Jalo x ESAL 686) x Jalo to the pathogen was evaluated. The F 1:3 RC 1 families were evaluated, in the absence of oidium, by grain yield (g/ plot), weight of 100 seeds (g) number of days to flowering and grain aspect. The association noticed of the reaction gene with grain aspect should not prevent the selection of resistant lines with grains similar to Jalo. DNA of F 1 RC 1 plants, resistant and susceptible, were pooled making up two bulks and amplified by RAPD. The four markers identified, amplified by the primers OPAC15, OPC14, OPC18 and OPL16, are closely linked among them and relatively far from the resistance allele, having little usefulness for indirect selection of resistant plants.

The genetic divergence of 27 common bean (Phaseolus vulgaris L.) cultivars from different races was evaluated using RAPD markers. The association of this divergence with some indirect variability estimates obtained in field experiments was also assessed. Genetic distances were calculated using Sorensen-Dice's similarity coefficient, displayed in a dendrogram (UPGMA method), and by projection in two-dimensional space. Analysis of molecular variance (AMOVA) was used to evaluate the distribution of variance between and within domestication centers. RAPD marker genetic diversity within these centers was also calculated. The correlations between estimates of genetic distances obtained with RAPD markers and estimates of Mahalanobis' generalized distances, specific combination ability, and midparent heterosis obtained from morpho-agronomical traits were also determined. RAPD markers were efficient in separating cultivars according to domestication centers. However, only for Middle American domestication center was there good agreement between the grouping obtained and the proposed classification of races. The genetic divergence obtained with these markers was similar to that provided by morpho-agronomical traits. RAPD markers, however, were not efficient in predicting the specific combination ability and midparent heterosis expressed in crosses.Avaliou-se a divergência genética de 27 cultivares de feijão (Phaseolus vulgaris L.) de diferentes raças, verificando-se ainda o grau de associação desta divergência com algumas estimativas indiretas de variabilidade obtidas em experimentos no campo. As distâncias genéticas foram obtidas pelo complemento do coeficiente de similaridade de Sorensen-Dice e a representação simplificada destas distâncias realizada a partir de um dendrograma (método UPGMA) e pela projeção no espaço bidimensional. Foi realizada uma análise de variância molecular para partição da variância entre e dentro dos centros de domesticação, e calculada a diversidade genética do marcador RAPD dentro destes centros. Também foram estimadas correlações entre as estimativas de distâncias genéticas obtidas a partir destes marcadores com estimativas de distâncias generalizadas de Mahalanobis, capacidade específica de combinação e heterose média, obtidas a partir de características morfo-agronômicas. Verificou-se que os marcadores RAPD foram eficientes na separação dos cultivares, de acordo com os centros de domesticação. Considerando as raças, no entanto, apenas para o centro de domesticação mesoamericano houve uma boa correspondência entre o agrupamento obtido e a classificação proposta. A avaliação da divergência genética por meio destes marcadores forneceu resultados similares aos obtidos, a partir de características morfo-agronômicas, mas estes não foram eficientes na predição da capacidade específica de combinação e da heterose dos cruzamentos.

This study compared severity of angular leaf spot in common bean lines, based on the healthy and diseased leaf area, and the graded scale. We used 12 common bean lines in the dry and rainy seasons. Two contiguous experiments were conducted in each season, with and without chemical control of the pathogen. We evaluated the percentage of the healthy and diseased leaf area; severity based on a graded scale and the area under the disease progress curve; and yield. The diseased or healthy leaf area is efficient to evaluate the severity of angular leaf spot with a sample of 20 to 30 leaflets per plot. For all traits, the results of central and border areas did not differ, indicating that the evaluation of border rows is unnecessary and, finally, the severity assessment of the upper plant half can discriminate the lines more efficiently. A severidade da mancha angular do feijoeiro foi avaliada com base nas áreas sadia e doente da folha e na escala diagramática. Foram avaliadas 12 linhagens de feijão nas épocas das secas e das águas. Em cada época foram conduzidos dois experimentos contíguos, com e sem controle químico do patógeno. Foram avaliadas as porcentagens das áreas sadia e doente da folha, severidade da doença segundo uma escala diagramática, área abaixo da curva sob progresso da doença e produtividade de grãos. As áreas sadia e doente da folha são eficientes para avaliar a severidade da mancha angular com uma amostra de 20 a 30 folíolos por parcela. A avaliação de todos os caracteres na área útil ou bordadura da parcela não difere, indicando que a bordadura por parcela é desnecessária. A avaliação da severidade na metade superior da planta discrimina as linhagens mais eficientemente.

A backcross breeding program between commercial common bean cultivars (VC3 and M20) and sources of resistance (Ex-Rico 23 and G122) was conducted with a view toward selecting carioca (beige with brown stripes) progenies resistant to white mold. Forty-eight progenies (27 F2:6 BC1 and 21 F1:5 BC2) were evaluated for yield, growth habit, grain type and pathogen response by two methodologies for assessment ("straw test" and "oxalic acid"). The methods were effective in discriminating the progenies, showing differing results, for they may assess different resistance mechanisms. Thus, they should be used together. Simultaneous selection for yield, growth habit, grain type and white mold resistance proved to be viable. The most appropriate strategy was to use lower intensities of selection and prioritize traits such as resistance and grain type, which are essential for commercial acceptance. Two progenies proved their superiority for the breeding program for they combine the traits of resistance and favorable grain type.

This study aimed to determine the minimum number of plants per plot to assess the field resistance in common bean to white mold. Thirteen cultivars were inoculated with six isolates of Sclerotinia sclerotiorum and evaluated in a randomized block design with three replications and plots consisting of 1-m rows with 15 plants. Plants were inoculated by the straw test as proposed by Petzoldt and Dickson (1996), to evaluate partial resistance in a greenhouse. Eight days after inoculation the disease severity was evaluated on a 1-9 diagrammatic scale, where 1 = asymptomatic plants to 9 = plant death. To determine the minimum number of plants per plot, the following methods were used: maximum curvature, segmented linear model, quadratic segmented model and the relative CV model. There were significant differences among cultivars and isolates and no significant cultivar - isolate interaction. It was observed that eight plants per plot is an adequate number to assess the reaction of common bean to white mold. O presente trabalho teve como objetivo determinar o número mínimo de plantas por plota para avaliar a resistência do feijoeiro ao mofo branco em campo. Treze cultivares foram inoculadas com seis isolados de Sclerotinia sclerotiorum. O delineamento utilizado foi o de blocos casualizados com três repetições, com plota constituída de quinze plantas por metro linear. A inoculação foi realizada utilizando o método do straw test. Oito dias após a inoculação foi realizada a avaliação utilizando uma escala diagramática de 1 (plantas assintomáticas) a 9 (morte da planta). Foram utilizados os métodos: curvatura máxima, modelo segmentado linear, modelo segmentado quadrático e o modelo CV relativo, para determinar o número mínimo de plantas por plota. Houve diferença significativa entre as cultivares, entre os isolados e entre a interação cultivares x isolado. Observou-se que oito plantas por plota é um número adequado para avaliar a reação de feijoeiro ao mofo branco.

Natural selection acts to select better adapted individuals or alleles in segregating population and help plant breeding. The objective of this work was to verify the effect of natural selection on microsatellite alleles as indicators of better adaptation and identification of quantitative trait loci (QTLs) for grain yield. This study evaluated 107 progenies from the F 8 and 107 from the F 24 generation derived from crossing Carioca MG and ESAL 686 lines, carried out by the bulk method, and evaluated in three different seasons: winter 2001; rainy 2001 and dry 2002. It utilized 22 polymorphic markers and the natural selection acted in all of them. The frequency of the alleles of the parent Carioca MG, the most adapted, was increased in all of the 22 loci in F 8 and 19 loci in F 24 . Selection affected each locus with different intensities in different generations. All of the selected alleles can be important for breeding program. QTLs were identified in generation F 8 and F 24 at varied magnitudes. The best marker PVttc002 explained 11.76% of variation in grain yield. However, an elevated interaction between QTLs and the environments was observed, showing the great difficulty in assisted selection.

The aim of this work was to identify the cooking capacity of grains from 23 common bean families already selected for high grain yield and grain type. They were derived from ESAL 693 x Rosinha cross and are all precocious, of type-I growth habit. The family seeds were from F 2:6 /F 4:6 generation (eight months old) and F 2:7 /F 4:7 (one month old); cooking and water absorption ability were evaluated using 25 seeds per plot, with two replications, through a JAB-77 experimental cooker, minor type. Cooking capacity and water absorption of the grains from the 23 families were genetically different and showed the same performance for both ages. Four families (1, 13, 14 and 15) presented high cooking capacity for both ages, among which 13, 14 and 15 distinguished for having high heritability estimates, making them the best choice for selection. No correlation was observed between the two traits, indicating that cooking capacity is the factor that should be evaluated for selection.