Tocher Optimization Research Articles

Agronomic Performance and Genetic Divergence in Corn (Zea mays) in the Cerrado-Amazon Ecotone

The objective of this work is to study the agronomic performance and genetic divergence in corn in the Cerrado-Amazon ecotone. The trials were conducted in the 2017/18 harvest at a property in the state of Pará. The experimental design was a randomized block with nine treatments and three replications, where the treatments are represented by nine cultivars of corn. The characteristics to evaluate agronomic performance and genetic divergence were: ear height (cm), plant height (cm), ear length (cm), ear diameter (mm), number of rows, number of grains per row and grain yield (kg ha−1). The cultivars were separated into a multivariate model in five groups using the Tocher optimization method. The cultivar AG 1051 showed the best agronomic performance. The results of genetic divergence were according to the generalized distance of Mahalanobis (D2), with the commences AG 8088 x CATIVERDE and AG 1051 x AL BANDEIRANTE, the most promising for future crosses.

IS THERE GENETIC VARIABILITY IN DWARF COCONUT ACCESSIONS PRESERVED IN BRAZIL?

ABSTRACT Dwarf coconut tree is the main variety for commercial use in Brazil, which ranks fourth in world coconut production. However, the genotypes used still have limitations and genetic variability is required. The aim of this study was to estimate the genetic variability in dwarf coconut accessions preserved at the Germplasm Bank of Brazil at different harvesting times and using agronomic descriptors of plant and fruits. The accessions Brazilian Green Dwarf-Jiqui, Cameroon Red Dwarf, Malayan Red Dwarf, Brazilian Red Dwarf-Gramame, Brazilian Yellow Dwarf-Gramame, and Malayan Yellow Dwarf were assessed by means of 30 descriptors Variance analysis was performed and the genetic diversity was quantified by using the Mahalanobis’ generalized distance and expressed by means of UPGMA clusters, Tocher optimization, and canonical variables. The maximum likelihood analysis was used to estimate the components of variance with the data of each plant in a sample of 11 descriptors of great importance for the genetic improvement of the coconut tree. A phenotypic divergence was found among the accessions using the UPGMA clusters, Tocher optimization and graphic dispersion obtained with canonical variables. The use of the maximum likelihood analysis confirms the existence of genetic variability in the accessions for the descriptors fruit polar and equatorial diameter, nut polar diameter, total fruit weight, and epicarp thickness, which presented a heritability varying from 0.17 to 0.39. There is a possibility of genetic gains with the selection of these traits for use of accessions in breeding programs.

Characterization of Open-Pollinated Maize Varieties from Rio Grande do Sul State

The morphological characterization allows one to estimate and evaluate the genetic distance among different varieties, identifying heterotrophic groups by means of clustering methods. The objectives of the study were to characterize improved open-pollinated varieties (VPAs) and maize landraces based on the main quantitative agronomic traits and to estimate the variability and similarity between them. Sixteen maize varieties from the southern region of the State of Rio Grande do Sul, Brazil were evaluated. Data were subjected to analysis of variance. For the characterization, the Tukey averages comparison test was performed. The similarity among the varieties was tested using the Tocher optimization method. The differences detected indicate the presence of genetic variability among the studied varieties. According to the Tocher grouping, it was found that some populations have the potential to be selected as parents in breeding programs, maximizing the variability obtained from their crosses. For certain traits, maize landraces do not differ from improved varieties and show high similarity.

Genetic diversity, agronomic potential and reaction to downy mildew in genotypes of biofortified mini lettuce

Lettuce is one of the most consumed leaf vegetables in the world, highlighting itself as a novelty in the market as mini type cultivars. During the winter the downy mildew can lead to severe damage. Thus, the objective of this work was to evaluate the genetic diversity, agronomic potential and downy mildew reaction in biofortified mini lettuce genotypes. The experiment was carried out in the University of Uberlandia, Monte Carmelo Campus. The statistical method used for the field experiment was the randomized complete block design, with 19 treatments (17 genotypes of the generation F3:4 and two cultivars of commercial lettuce) and two repetitions. The following parameters were evaluated: crowndiameter (cm); rod diameter (mm); number of leaves per plant and spad index. The data were submitted to multivariate analyses were performed. The genetic divergence was represented by dendrogram obtained by the hierarchical UPGMA method and by the Tocher optimization method. The laboratory experiment was carried out in a completely randomized design with 18 genotypes, two Bremia lactucae breeds (3 and 4) and three repetitions. In order to select resistant genotypes, inoculations were carried out, using distilled water mixture with the sporangia of the pathogen and Tween 20. The monitoring was performed daily and when the first sporulation appeared on cotyledonary leaves of the susceptible cultivar, the genotypes were evaluated, verifying the presence or not of sporulation and necrosis. The use of Mahalanobis distance Dii2 as a measure of dissimilarity allowed the formation of two groups by the Tocher method. The grouping of the accesses by the UPGMA hierarchical method formed four groups, with the cut-off point established at the 7% similarity distance. The all lettuce genotypes F3:4 showed low percentage of necrotic plants and sporulated plants.

Agrupamento multivariado de curvas na desidratação em raízes de batata-doce

Minimizing post-harvest losses during sweet potato storage is imperative for the producer and consumer. Therefore, the use of statistical tools to select the superior genotypes that have good post-harvest characteristics will contribute to breeding programs. The aim of this study was to demonstrate the applicability of the multivariate clustering technique as an alternative in the post-harvest study on root dehydration among sweet potato accessions. A total of 74 accessions of sweet potatoes were evaluated in a randomized complete block design in four replicates. The roots were stored in plastic boxes at room temperature and the loss of fresh matter was measured on times 0, 4, 8, 12 and 16 days after harvest. The multivariate clustering was based on the Euclidean distance and the Tocher optimization method on adjusted curves using linear and nonlinear models. The non-linear best fit model was Brody, which allowed the discrimination of accesses with higher and lower dehydration. The multivariate grouping of curves was efficient in the post-harvest study on sweet potato access roots.

Genetic diversity of promising 'conilon' coffee clones based on morpho-agronomic variables.

Knowledge of the genetic variability of a population is essential to guide its preservation and maintenance in addition to increasing the efficiency of genetic breeding programs. On this basis, this study was conducted to evaluate the genetic diversity of Coffea canephora genotypes using multivariate statistical procedures applied to a set of morpho-agronomic variables. The materials employed in this study constitute a crop located in Vila Valério - ES, Brazil, where the genotypes are arranged in a randomized-blocks experimental design with four replicates. Significant differences were detected by the F test at the 1% or 5% probability levels among the genotypes for all evaluated traits, demonstrating heterogeneity of genetic constitution in the studied population, which is favorable to breeding, as it indicates the possibility to identify superior and divergent individuals. Based on the generalized Mahalanobis distance, the most divergent combinations were obtained between genotypes 23 and 10 (256.43) and 23 and 17 (250.09). The clusters formed by Tocher's optimization and the UPGMA hierarchical method agreed, both similarly grouping the genotypes into three clusters. Of the analyzed traits, mature fruit weight (19.08%), yield (15.50%), plant diameter (12.42%), and orthotropic-shoot internode length (10.94%) were the most efficient to explain the dissimilarity among the genotypes.

Research Article Genetic diversity among accessions of Capsicum annuum L. through morphoagronomic characters

Genetic variability among pepper genotypes is essential in obtaining hybrid combinations with greater heterotic effect and in obtaining superior strains. This work’s goal was to evaluate the genetic diversity between accessions of Capsicum annuum L., indicating the selection of promising individuals for ornamental purposes. The experiment was carried out in at the Plant Biotechnology Laboratory of the Center of Agricultural Sciences, Federal University of Paraiba. The experiment was conducted in a completely randomized design with 16 treatments and eight replications. The plants were evaluated for 28 morphoagronomic traits. Data were submitted to analysis of variance and grouped according to Scott and Knott's test at 1% probability. The Tocher grouping was performed based on Mahalanobis distance and analysis of canonical variables were performed with graphical dispersion of the accessions. All variables were significant by the F test (p = 0.01) and presented high heritability and a CVg/CVe ratio higher than 1.0 for most traits, indicating genetic divergence between accessions. In keeping with the Scott-Knott's test (p = 0.01), the accessions were grouped into two to eight classes, varying according to the character. The of Tocher optimization method separated the accessions into five distinct groups. There is phenotypic divergence between the accessions of Capsicum annuum L. which can be used in ornamental peppers’ breeding programs. Only the number of stamens trait presented a heritability value (65.81%) lower than 70%. The characters that most contributed to divergence among the accessions were fresh fruit mass, stem diameter, widest fruit diameter and fruit weight. The accessions UFPB001, UFPB004, UFPB45, UFPB77.3, UFPB099, UFPB134, UFPB390 and Calypso are designated as potential accessions for ideal ornamental pepper plant with vigorous seedling, small port, large flowers and small fruits. Ornamental pepper accessions with larger anthers are indicated for selection, for facilitating the breeder’s work during flower emasculations for crossings.

Genetic diversity analysis in selected germplasm lines of safflower (Carthamus tinctorius L.)

In the present study, a total of 155 genotypes along with five checks ‘A-1, PBNS-12, AKS-207, PKV Pink, Bhima ’were assessed to study the genetic diversity among the genotypes. These genotypes were grouped into eleven clusters based on the measurements of genetic divergence obtained by means of Mahalanobis distance (D2) and in the grouping by Tocher optimization method. The average inter cluster distance was maximum between clusters VI and IX (7037.21) followed by clusters III and IX (6895.24), clusters IX and XI (6756.33), clusters IX and X (5760.02), clusters VII and IX (5724.53) which indicated that the genotypes included in these clusters may give high heterotic responses and thus better segregants. The present study projected the importance of GMU-4502, GMU-4934, GMU-4507 as parents for higher heterosis in F1 and potential transgressive segregants in subsequent generations as they have least mean values for days to 50% flowering, days to maturity whereas high mean values of GMU-4839, GMU-4934, GMU-40, GMU-5032, GMU-2969, GMU-5663 and GMU-3740 for characters viz. plant height, number of primary branch per plant, number of capitula per plant, volume weight, 100-seed weight, seed yield per plant and oil content respectively suggest their further improvement in respect to these yield attributing characters.

Genetic dissimilarity and relative importance of characteristics in banana cultivars through multivariate analysis

One of the problems of banana cultivation is the reduced number of productive commercial cultivars, with fruits adequate to market requirements. This paper aimed to study the genetic divergence among 15 banana cultivars by multivariate analysis and determine the relative importance of 35 agronomic and nutritional characteristics. The data were subjected to multivariate analysis of variance. For the application of Tocher Optimization grouping method, the Mahalanobis distance was used. The hierarchical method UPGMA and canonical variables analysis were also used. For the identification of the most important characteristics for dissimilarity, was used the Singh method. There was a higher mean dissimilarity to cultivate Terrinha followed by Marmelo cultivars and Mysore. The smallest measure of dissimilarity was found between the Nanicao and Prata-Grauda cultivars. The characteristics vitamin A content, starch percentage, total soluble sugars, sugars, non-reducing, antioxidant potential, fresh weight of pulp, plant height and fresh weight of the fruit are the most important in the estimation of dissimilarity, are soon to be prioritized in studies future.

GENETIC DIVERSITY OF PASSIFLORA ACCESSIONS BASED ON MORPHOPHYSIOLOGICAL SEED DESCRIPTORS

ABSTRACT The aim of this work was to estimate the genetic divergence among Passifloraaccessions based on morphophysiological seed characteristics. Accessions were distributed in a completely randomized design, with four replicates of 25 seeds. Data were submitted to analysis of variance and the means grouped by the Scott-Knott method. The genetic diversity was studied according to the Tocher and UPGMA grouping method based on the Mahalanobis distance (D2) and Canonical Variables. In the cluster analyzes, four groups were formed by the UPGMA and Canonical Variables methods. In the Tocher Optimization method, seven groups were formed. of P. eichleriana, P. suberosa, P. edulis and P. foetida accessions presented the best results for the seed characteristics under study, being indicated for interspecific crosses aiming the selection of materials that present less dormancy and with more vigorous seeds.

Genetic divergence between passion fruit hybrids and reciprocals based on seedling emergence and vigor

Abstract: Characteristics related to seed quality have been rarely used in studies on the genetic diversity of passion fruit. The purpose of this study was to evaluate the genetic diversity between progenies constituted by hybrids and reciprocals, based on seed emergence and vigor traits. On the 28th day, emergence percentage, emergence speed index, shoot length, root length and total length of seedling; dry weight, number of normal seedlings and 100-seed weight were evaluated in a completely randomized design experiment with 20 progenies (hybrids and reciprocals) and four replications (50 seeds). Genetic diversity was determined using the Tocher optimization clustering methods and the unweighted pair group method, based on the Mahalanobis distance, as well as evaluating the relative contribution of the traits to genetic divergence and the correlation network, according to the relations between groups of quality, length and mass variables. The most contributing variable to genetic divergence was the total length of seedlings, the reciprocal effect did not present a consistent pattern in the studied hybrid combinations.

English

Genetic diversity studies provide fundamental information for characterization, conservation and utilization of available genetic resources in plant genetic improvement programs. To evaluate the genetic divergence among papaya accessions, 17 morphoagronomic variables from 59 accessions of the active germplasm bank were evaluated in an experiment at Santa Teresinha Farm, belonging to Caliman Agrícola S/A, in Linhares-ES, Brazil. The experiment was conducted in a randomized block design with two replicates. The divergence between the accessions was estimated using the Tocher optimization method and the agglomerative hierarchical approach based on the Unweighted Pair-Group Method Using an Arithmetic Average. (UPGMA). There was significant difference for all the variables evaluated, showing variability among the accessions. The variables plant height, first fruit insertion height, greatest thickness of fruit pulp, fruit diameter, and fruit length had heritability above 80%, indicating expressive gains in the simple process of selection. Genetic variability was found among the accessions, and Americano, short-peduncle-STZ-03 and Califlora 209 were the most divergent. The optimization methods Tocher and hierarchical based on UPGMA were partially concordant for the formation of heterotic groups of papaya accessions. The variables fruit mass, fruit diameter and plant height contributed the most to the genetic diversity.   Keywords: Carica papaya L., genetic variability, multivariate analysis.

GENETIC DIVERGENCE AMONG COTTON GENOTYPES GROWN IN THE MAIN SEASON AND OFF SEASON

ABSTRACT The objective of this work was to evaluate the agronomic performance and estimate the genetic divergence of 18 cotton genotypes grown in the main season (sowed in December, 2012) and off season (sowed in January, 2013), considering their agronomic characteristics and resistance to Ramularia leaf spot. A randomized block experimental design was used, with five replications. The characteristics evaluated were plant height, first branch height, position of first fruiting branch, height of first fruiting branch, length between nodes, number of nodes, average number of bolls per plant, average boll weight, area under the disease progress curve (AUDPC) related to the Ramularia leaf spot severity, weight of 100-seed from the plant middle third, fiber percentage, average production per plant, yield and cotton fiber quality. The results were subjected to individual and joint analysis of variance and the genetic divergence was estimated according to multivariate procedures (Mahalanobis' generalized distance and Tocher's optimization method). The dissimilarity matrices were summed to estimate the genetic divergence, considering both growing periods. Genetic variability was found among the genotypes evaluated, in both the main season and off season. The characteristic that most contributed to the genetic divergence in the main season was the production per plant and, in the off season, was the fiber percentage. According to the results of the present work, the crosses between the genotypes BRS-335 and FMT-707; FM-910 and FMT-707; and IMA-08-12427 and FMT-707 are recommended.

Agro-morphological characterization and genetic divergence assessment in bush snap bean genotypes1

ABSTRACT The characterization and identification of genetically divergent parents for crosses are important tasks in snap bean breeding programs, for a greater availability of cultivars to growers. This study aimed at characterizing bush snap bean genotypes originating from different countries; assessing the genetic divergence between the genotypes and the genetic variability extent, concerning 12 agro-morphological traits; and determining the relative importance of these traits for the genetic divergence. The experiment was conducted in a randomized complete block design, with 29 genotypes and four replications. The UPGMA and Tocher optimization methods, both based on the generalized distance of Mahalanobis, and the canonical variables method were used to analyze the genetic divergence. The genotypes exhibited a wide range of genetic variability for the agro-morphological traits evaluated, mainly for 100-seed weight, aspect and yield of commercial pods, plant height at harvest and pod weight. A high genetic divergence was detected between the genotypes, in which the 100-seed weight and aspect of commercial pods were the most important traits for clustering. Some genotypes own desirable characteristics for these and other traits, given the favorable genetic associations between traits. The snap bean genotypes originated from different countries tended to cluster together, indicating that similar germplasm is shared among different countries, thus suggesting a strong trans-national seed exchange.

Index proposal for Nelore bulls classification using traits groups of weight, carcass and reproductive

Genetic breeding programs generally evaluate animals considering the same objectives, but the indices used in the selection criteria can vary. This can give rise to distinct bull rankings in each program. Thus, we aimed to create alternatives for the referral of bulls for mating through multivariate analyses. We used information from the summaries of two genetic evaluation programs (1 and 2) with Nellore bulls. Characteristics were separated into groups: weight, carcass and reproduction. Groups were formed using the mean Euclidean distance and the Tocher optimization method. The means of each trait among the animals allocated to the same group were used to compose the following subindexes: weight gain (siWG), carcass (siCG) and reproduction (siRG). Based on the mean of the group subindex classification, we calculated the average index of group classification (iAGc). When classifying the best groups by characteristics, we observed an increase (superiority of some bulls) in the estimated breeding values (EBVs) by comparison with the total number of bulls evaluated by the programs, selected animals and best 10 final indexes of the programs. There was a change in bull classification when using the iAGc in relation to the classification using the final indexes of the programs. The coefficient of simple coincidence showed that there was a change in bull classification between programs, both between deciles of the final indexes and groups of characteristics. The subindexes siWG, siCG and siRG are important for correcting specific problems in herds. The iAGc should be used instead of the final index of the programs, providing more options for the selection of bulls for mating.

Evaluation of genetic diversity among soybean (Glycine max) genotypes using univariate and multivariate analysis.

The genetic diversity study has paramount importance in breeding programs; hence, it allows selection and choice of the parental genetic divergence, which have the agronomic traits desired by the breeder. This study aimed to characterize the genetic divergence between 24 soybean genotypes through their agronomic traits, using multivariate clustering methods to select the potential genitors for the promising hybrid combinations. Six agronomic traits evaluated were number of days to flowering and maturity, plant height at flowering and maturity, insertion height of the first pod, and yield. The genetic divergence evaluated by multivariate analysis that esteemed first the Mahalanobis' generalized distance (D2), then the clustering using Tocher's optimization methods, and then the unweighted pair group method with arithmetic average (UPGMA). Tocher's optimization method and the UPGMA agreed with the groups' constitution between each other, the formation of eight distinct groups according Tocher's method and seven distinct groups using UPGMA. The trait number of days for flowering (45.66%) was the most efficient to explain dissimilarity between genotypes, and must be one of the main traits considered by the breeder in the moment of genitors choice in soybean-breeding programs. The genetic variability allowed the identification of dissimilar genotypes and with superior performances. The hybridizations UFU 18 x UFUS CARAJÁS, UFU 15 x UFU 13, and UFU 13 x UFUS CARAJÁS are promising to obtain superior segregating populations, which enable the development of more productive genotypes.

Genetic dissimilarity of common bean lines for agronomic and biofortification traits

The evaluation of the genetic dissimilarity of common bean lines obtained by the breeding program is significant to identify duplicate accessions, to select superior lines, and to plan new hybrid combinations. The objectives of this study were to evaluate the genetic dissimilarity of common bean genotypes for agronomic and mineral biofortification traits, select superior lines, and identify promising hybrid combinations for biofortification programs. For this purpose, 169 common bean genotypes (F6:8 inbred lines and parental cultivars) were evaluated in two experiments conducted in a simple lattice design in Santa Maria-RS, Brazil. The following agronomic traits were evaluated: insertion of the first pod, insertion of the last pod, cycle, mass of 100 grains, grain yield, and concentrations of potassium, phosphorus, zinc, and copper in grains. The genotypes assessed presented genetic variability for all traits, except for copper concentration in grains. The traits that showed the highest contribution to the genetic dissimilarity were the concentrations of phosphorus, potassium, and zinc in grains. In cluster analyses, six groups by principal components and 33 groups by the Tocher optimization method were identified. These methods partially agreed in the formation of different groups of common bean genotypes. Controlled crossings between the lines 17 and 162 with lines of groups XX, XXI, XXIV, and XXXIII are recommended to obtain recombinants with high grain yield and biofortified for phosphorus, potassium, and zinc.

Genetic variability among common black bean (Phaseolus vulgaris L.,) accessions in southern Brazil

To obtain superior genotypes, the use of natural genetic variability is essential, aiming to select parents that will make future crossings blocks. Therefore, the aim of this study was to determine the genetic variability and dissimilarity using multivariate analyzes in common black bean accessions native to southern Brazil. The experiment was conducted in the 2014/2015 in Frederico Westphalen – RS. The experimental design was augmented blocks (RCBD) with four repetitions (totally 149 treatments), in which 147 black common bean accessions were evaluated. Two commercial cultivars were used as witnesses: BRS Esplendor and BRS Supremo. The phenotypic traits such as days to flowering, plant height at flowering, days to maturity, plant height at maturity, insertion of the first pod, number of pods per plant, number of seeds per pod, mass of seeds per pod, number of branches, mass of seeds per plant, seed length, seed width, seed flattening, seed brightness, presence of halo, color of the halo were measured. The distributions of phenotypic frequencies indicate genetic variability among the 149 genotypes of common black bean. The Tocher optimization method presents the formation of eight groups of genotypes. The dendrogram formed by the standardized Euclidean distance was efficient in the stratification of the accessions for their genetic distance. The relative contribution evaluated by Singh method shows that the characters days to flowering and seed brightness are those that best discriminate the genotypes. The multivariate techniques of Tocher optimization and the standardized Euclidean distance show similar responses, proving to be viable tools for the choice of parents in a breeding program.

Analysis of the genetic divergence of soybean lines through hierarchical and Tocher optimization methods.

This study aimed to evaluate the clustering pattern consistency of soybean (Glycine max) lines, using seven different clustering methods. Our aim was to evaluate the best method for the identification of promising genotypes to obtain segregating populations. We used 51 generations F5 and F6 soybean lines originating from different hybridizations and backcrosses obtained from the soybean breeding program of Universidade Federal de Uberlândia in addition to three controls (Emgopa 302, BRSGO Luziânia, and MG/BR46 Conquista). We evaluated the following agronomic traits: number of days to flowering, number of days to maturity, height of the plant at maturity, insertion height of the first pod, grain yield, and weight of 100 seeds. The data was submitted to analyses of variance followed by average Euclidean distance matrix estimation used as measure of dissimilarity. Subsequently, clusters were formed using the Tocher method and dendrograms were constructed using the hierarchical methods simple connection (nearest neighbor), complete connection (most distant neighbor), Ward, median, average within cluster connection. The nearest neighbor method presented the largest number of genotypes in group I and showed the greatest similarity with the Tocher optimization method. The joint use of these two methodologies allows for differentiation of the most genetically distant genotypes that may constitute the optimal parents in a breeding program.

English

Safflower (Carthamus tinctorius L.) is a crop that produces oil with high content of oleic and linoleic acids, which has great quality for human consumption and industrial use, such as in biodiesel production, and cosmetics and pharmaceuticals. The objective of this study was to quantify the genetic diversity among 20 safflower genotypes by morphological characteristics. The genotypes were grouped into nine groups based on the measurements of genetic divergence obtained by means of Mahalanobis distance (D2) and in the grouping by Tocher optimization method. Heritability coefficients ranged from 89 to 93% and b quotient was above 1.0 indicating that the variability in the population allows obtaining genetic gains for all traits. Grain yield is the character that most contributed to the genetic variability of the population studied. The accesses of Group V are favorable for use as parents in crosses to obtain new genotypes with high grain and oil yields, and desirable plant architecture.   Key words: Safflower, plant breeding, multivariate analysis, genetic variability, genetic parameters.