Tocher Optimization Method Research Articles

Rumen Content from Slaughterhouse as an Alternative Inoculum Source for In Vitro Analysis of Feeds: A Multivariate Approach

The objective of the current study was to compare the rumen inoculum of slaughtered cattle with the ruminal inoculum of cannulated cattle; additionally, determine its reliability in the in vitro analysis of ruminant feeds throughout a multivariate approach. Five male bovines (weight 320 ± 9.4 kg; mean ± standard deviation) provided with ruminal cannula and between five and seven bovines slaughtered in slaughterhouse were used. The evaluations were carried out following a completely randomized design. The data obtained were subjected to different multivariate analyzes to determine the reliability of the ruminal inoculum of animals slaughtered in commercial slaughterhouses compared to that obtained from cannulated animals. The relative contribution indicated that the in vitro dry matter digestibility (IVDMD, 50.75%) and in vitro neutral detergent fiber digestibility (IVNDFD, 29.83%) analysis influence 80.13% of the results to determine the reliability of the ruminal inoculum from slaughtered cattle. Furthermore, it was determined that the first two principal components (IVNDFD and acetic acid production) are the ones that influence the results by 89.87%. The grouping of diets using the Tocher optimization method and the dendrogram shows the formation of six groups and two groups, respectively. The grouping shows that the ruminal inoculum source was not the limiting parameter in the evaluation. Rumen inoculum from cattle slaughtered in a commercial slaughterhouse (with unknown diet) has potential as an alternative for the in vitro analysis of cattle feed, provided that the lignin concentration in the diet is less than 35.5 g/kg DM.

Genetic Divergence and Selection of Genitors Aiming to Generate Variability in Common Bean Lines

The objective of this work was to evaluate the genetic divergence between common bean strains from the breeding program of the Agricultural Research Institute of Mozambique (IIAM)-Zonal Centre (CZC) and to identify potential genitors to generate segregating populations with high average and wide genetic variability. Five common bean lines were evaluated in a randomized block design with three repetitions. The quantitative traits evaluated were leaf area index, days to 50% flowering, days to maturity, several pods per plant, 100 seed weight, and yield, while the qualitative traits were growth habit, epicotyl colour, leaf colour intensity, leaf roughness, fresh pod colour, grain colour, grain size, and flower colour. The data obtained were submitted to variance analysis and grouping of means by the Scott-Knott test. The relative importance of characters was evaluated by the Singh. Clustering was performed by the Tocher optimization method and distance projection in the 2D plane, using the generalized Mahalanobis distance as a measure of dissimilarity. The degree of preservation of genetic distances in the 2D plane was assessed by the Cohenetic Correlation Coefficient, distortion, and stress. The LPA54 and Bonus lines were highlighted by direct selection based on the performance per se of their characteristics. Genetic variability was checked for the trait’s days to 50% flowering several of pods per plant, and 100-seed weight and the strains were separated into two groups. The crosses between (G19833, LPA54, Manteiga, and Bonus) with the strain DOR364 there is the potential for obtaining hybrids with higher heterotic effect and segregating populations with high variability. The traits of 100-seed weight, pods per plant, epicotyl colour, and grain size were the most important in the discrimination of the strains

PARAMETERS AND GENETIC VARIABILITY IN BLACK BEANS F5 FAMILIES

The objective of this work was to contrast expectations of the segregating generations F2, F3, F4, and F5 with homozygous genetic constitutions, to determine the genetic parameters, dissimilarities through multivariate models, and the associations between characters of agronomic importance for the breeding of black beans. The experiment was conducted in the 2017/2018 crop season in the county of Tenente Portela – RS, Rio Grande do Sul, Brazil. The experimental design used was that of augmented blocks, with the cultivars IAC Imperador, IPR Tangará, BRS Estilo composing the common treatments, considered as pure lines, and 131 lineages of the F5 segregating generation, composing the unusual treatments, arranged in three blocks. After the characterization of the 134 genotypes, it was possible to verify that through Singh's relative contribution, the character of number of seeds per plant was the most decisive for the genetic variability of this study. The use of biometric methods allows it to be possible to evidence patterns in relation to the genotype clusters, through the use of standardized average Euclidean distance patterns, Tocher's optimization method, UPGMA clustering method, and Artificial Neural Networks with unsupervised learning. With the results obtained, it was possible to verify the existence of genetic variability among the studied populations, allowing the cluster analysis to delimit

A contribution to the physicochemical characterization of Eugenia involucrata DC. fruits to estimate genetic variability

Brazil has one of the greatest diversities in native fruit trees, but many species, despite the great environmental and economic potential for small farms, are little studied, such as the cherry-of-the-rio-grande (Eugenia involucrata DC.). The hypothesis of this research was that there is a high genetic diversity due to the propagation by seeds, occurring genotypes that produce better quality fruits which can be used to implement genetic improvement programs and the production of seedlings with better productive performance. So, this study aimed to characterize fruits of this species' genotypes and to evaluate the genetic divergence applying multivariate analysis techniques. Genotypes of different ages found in rural and urban areas of the municipality of Serafina Corrêa, Rio Grande do Sul, were evaluated, with 50 genotypes in 2018 and 38 genotypes in 2019, since twelve did not bear fruit. Data were submitted to determine the mean and standard deviation. To assess genetic diversity, the relative contribution of characters was determined by the Singh method; the average Euclidean distance standardized matrix (UPGMA) and dendrograms were generated; and Tocher's optimization method was applied. Results showed that UPGMA and Tocher clustering methods are more efficient in representing the diversity between genotypes. Fruits characteristics varied from one year to another, due to the combination of biotic and abiotic factors (water regime), resulting in changes of characters with greater contribution in the divergence and formation of similar groups. The content of total soluble solids (TSS) in 2018 and fruit mass in 2019 harvest were characters that most contributed to the genetic divergence. It was concluded that the physicochemical characters of fruits revealed the existence of genetic divergence among genotypes, allowing the selection of agronomically superior plants.

Genetic Divergence and Selection of Common Bean Genotypes with High Agronomic Performance in Mozambique

The deep knowledge of genetic diversity in access, in the breeding program, and the contribution of genetic factors as well as the phenotypic expression is of extreme importance for the development of new cultivars and maintenance of the program. This research aimed to study the genetic diversity and selection of the best common bean genotypes with high agronomic performance in the Agrarian Station of Sussundenga-Mozambique. Twenty-two common bean genotypes were evaluated in a randomized block design with three repetitions in the 2021/2022 agricultural season. The agronomic characteristics evaluated were: the number of days to flowering, plant height, plant architecture, number of pods per plant, the weight of 100 seeds, and grain yield. The data obtained were submitted to individual variance analysis, followed by the Scott-Knott grouping test. For the effect of genetic divergence between the genotypes, multivariate analysis was used based on the generalized Mahalanobis distance and Tocher optimization method, UPGMA, and canonical variables for the projection of distance in the 2D plane. It was also verified by the Cophenetic Correlation Coefficient. The Singh criterion (1981) was used, indicating the characteristics Number of pods per plant (42.81%), the weight of 100 seeds (19.59%), and Plant height (16.08%) as the most important for the genetic divergence of bean genotypes.

Genetic divergence based on leaf vegetative and anatomical traits of Coffea canephora clones

Knowledge of the expression of traits associated with drought tolerance is important to mitigate impacts on coffee production in a climate change scenario. This study aimed to understand the genetic divergence between Coffea canephora genotypes grown in the Western Amazon based on leaf vegetative and anatomical traits. For this, fifteen high-performance genotypes were evaluated in a randomized block design with five replications of one plant per plot to analyze three leaf vegetative traits (leaf area index, root volume, and total dry mass) and five leaf anatomical traits (polar and equatorial diameter, density and number of stomata, and stomatal area). The data were interpreted using analysis of variance and the Scott-Knott mean cluster test (p ≤ 0.05). The Tocher optimization method and principal component analysis with reference points were used to quantify the genetic divergence. Tocher clustering separated the fifteen clones into five groups, and the scatter in the plane into three groups. Stomatal density was the trait that most contributed to the dissimilarity between genotypes with the potential to be used in future studies for the selection of water deficit-tolerant genotypes. The BRS 3213 genotype showed the greatest genetic dissimilarity and composed a group isolated from the other genotypes in terms of anatomical characteristics. Hybrids 12 and 15 have leaf anatomical traits with higher drought tolerance potential.

Floral morphology of robusta coffee genotypes

AbstractKnowledge about the diversity in the morphological characteristics of robusta coffee (Coffea canephora Pierre ex Froehner) flowers is fundamental to understanding reproduction processes, interpret pollination‐related mechanisms, and contribute to breeding studies. The objective of this study was to analyze and characterize morphological variability of flower traits among robusta coffee cultivar Conilon genotypes of high agronomic performance. The experiment was arranged in a randomized block, split‐plot design. The main plot corresponded to six Conilon coffee genotypes and the subplots to 2 yr of evaluation (2018 and 2019). Eight floral traits were measured and analyzed through analysis of variance by the F test (<.01), Tocher's optimization method and hierarchical Unweighted Pair Group Method using Arithmetic Averages (UPGMA) clustering. The relative importance of each character was also estimated to predict genetic diversity, and the degree of trait interrelation was assessed by Spearman's correlation. Genotype Pirata had outstanding floral morphological structure and was grouped separately by Tocher and UPGMA clustering. Style length was the major contributor to genetic diversity, followed by the lengths of the corolla tube and stigmatic lobes. The flower trait characteristics were positively correlated, and corolla tube length and style length were most strongly correlated. These results contribute to other studies related to the interpretation of the mechanisms related to pollination and reproduction of this species, and also outline diversity of genetic resources of interest to plant‐breeding programs.

Caracterização morfoagronômica de genótipos de feijoeiro comum quanto à precocidade

O feijoeiro comum é uma cultura de grande importância alimentar, econômica e social, em termos de produção e consumo, é uma leguminosa herbácea, com ciclo em torno de 95 dias, a maioria das cultivares utilizadas para o cultivo no mercado brasileiro expressa grande variabilidade genéticas quanto ao início de florescimento e a duração total do ciclo. Diante disso, objetivou-se com este trabalho avaliar a caracterização morfoagronômica de genótipos de feijoeiro comum quanto à precocidade de cultivo. O experimento foi conduzido na EMAPER, no município de Cáceres-MT, adotando o delineamento experimental em blocos ao acaso com três repetições, avaliando 58 genótipos de feijão comum. As parcelas foram compostas por quatro linhas de 4 m, com espaçamento de 0,5 m entre linhas. As características avaliadas foram o número de dias para o florescimento e ciclo de cultivo, os dados foram submetidos à análise de variância e a comparação das medias pelo teste de agrupamento Scott-Knott a 1% de probabilidade. A divergência genética foi estimada método de otimização de Tocher e hierárquico UPGMA, baseada na Distância Generalizada de Mahalanobis utilizando o programa computacional GENES. Pode-se concluir que existe variabilidade genética entre os genótipos de feijão comum avaliados, e os genótipos 3 (BG-UNEMAT-11) e 57 (TB 02-23) apresentaram menor número de dias para florescimento (31 dias) e menor ciclo da cultura (73 a 82 dias), sendo os mais indicados para programas de melhoramento genético visando precocidade.

Characterization and genetic diversity of Coffea canephora accessions in a germplasm bank in Espírito Santo, Brazil

Abstract: The state of Espirito Santo is the major producer of Coffea canephora in Brazil. Knowledge of genetic reserves is fundamental to plant breeding. Therefore, the present study characterized and analyzed the genetic diversity of 600 C. canephora accessions from the germplasm bank of Incaper based on 38 traits evaluated in 24-30-month-old plants. Further, the predominant descriptors or traits were identified, and high phenotypic variability was determined. Genetic distances for the grouped (Gower), quantitative, and qualitative datasets were 0.48, 0.61, and 0.92, respectively, with accessions 76 (Conilon) and 407 (Robusta) being the most divergent ones at Incaper. In clustering using the Tocher optimization method, 30 groups were formed, with three accessions introduced from Epamig’s Robusta collection being the most dissimilar ones. Graphical dispersion analysis using the principal coordinate method revealed the predominance of three groups formed by the Robusta, Conilon, and hybrid Robusta × Conilon genotypes.

Divergência genética entre tipos especiais de arroz a partir de técnicas multivariadas

O mercado brasileiro de arroz prioriza o consumo de arroz branco polido. Entretanto, existem demandas por tipos especiais. A estimativa da divergência genética é importante para o melhoramento genético, pois permite a seleção de genitores em sistemas de cruzamentos controlados. Assim, os objetivos deste trabalho foram indicar a contribuição relativa dos caracteres avaliados para a dissimilaridade genética e avaliar a divergência genética entre genótipos de tipos especiais de arroz por dois métodos diferentes de agrupamento. O experimento foi conduzido no ano de outubro de 2012 a março de 2013, na UFRRJ, Seropédica, RJ. O delineamento utilizado foi em blocos ao acaso, com cinco repetições. Os tratamentos constaram dos genótipos Caiapó, Vermelho Pequeno, IAC 300, IAC 400 e IAC 500. A medida de dissimilaridade adotada foi a distância euclidiana. Foram utilizados dois métodos diferentes de otimização: o método de otimização de Tocher e o método hierárquico UPGMA (Unweighted Pair-Group Method using Arithmetic Avarages). Os genótipos Caiapó e Vermelho Pequeno estiveram em diferentes grupos heteróticos em relação aos genótipos IAC 300 e IAC 400, independentemente do método de agrupamento utilizado. Verificou-se que a característica produtividade foi a que mais influenciou na variação total.

Agronomic potential and genetic dissimilarity among coffee cultivars: Hierarchical method and optimization

The coffee growing in Minas Gerais has been outstanding due to the high quality in the production and the cultivar choice is very important during the culture implantation process. Genetic dissimilarity studies are very important to make further advances in breeding programs to obtain more adapted cultivars. Thus, the objective of this work was to evaluate the agronomic potential and genetic dissimilarity among coffee cultivars based on hierarchical and optimization methods. The experiment was installed at the Federal University of Uberlândia, Campus - Monte Carmelo. The planting was carried out in December 2015, using a randomized block design with four replications. A spacing of 3.5 m between rows and 0.6 m between plants was adopted. The treatments consisted of the Coffea arabica cultivars: Acaiá Cerrado - MG 1474; Mundo Novo IAC 379-19; Bourbon Amarelo IAC J10; Catuaí Vermelho IAC 99; Topázio MG 1190; Acauã Novo and IAC 125 RN. Growth, crop yield and physical classification were evaluated for type, size and shape of coffee beans. There was consistency between hierarchical and optimization methods in the groups formation. The cultivar Mundo Novo IAC 379-19 showed the highest vegetative vigor. The cultivar Acaiá Cerrado MG 1474 was the one that obtained the highest yield in the first crop. The cultivar Topázio MG 1190 showed higher genetic dissimilarity compared to the other cultivars. UPGMA multivariate analysis and Tocher optimization methods indicated that the cultivars have genetic variability for the region under study.

Genetic divergence in biomass sorghum genotypes through agronomic and physical-chemical characters

The present research aimed to evaluate the genetic divergence in 34 sorghum biomass genotypes via agronomic and physicochemical characters. The design used was randomized blocks with three replications. The agronomic and physical-chemical characteristics evaluated were: days for flowering, number of stems, plant height, number of leaves, green mass production, dry mass production, determination of total ash, determination of volatile content, insoluble lignin and determination of fixed carbon content. The data were submitted to analysis of variance and then, to estimate divergence, the generalized Mahalanobis distance was used as a measure of dissimilarity. Based on this matrix, the methods of Tocher's optimization clusters and the Hierarchical method of Average Grouping Between Groups (UPGMA) were used, and analysis of canonical variables, and the projection based on the first two canonical variables arranged in two-dimensional space. Singh criterion was also used to quantify the relative contribution of these characteristics to genetic divergence. The evaluated genotypes showed significant differences for all the evaluated characteristics. The combination between the 201429B001 and 201429B028 (394.98) genotype pairs was the most divergent and the combination between the 201429B015 and 201429B031 (6.31) genotypes was the most similar. The grouping generated by the Tocher Optimization method, hierarchical UPGMA and graphical dispersion showed similarity in the grouping of genotypes. The first two canonical variables were sufficient to explain about 81.78% of the total variation observed. The results showed a wide genetic diversity among the 34 genotypes of sorghum biomass.

Genetic Divergence in Corn Genotypes for High and Low Phosphorus in Pará, Brazil

Aims: The objective of this study was to estimate the genetic divergence between ten corn genotypes in the 2017/18 crop, under high and low phosphorus.
 Study Design: The experimental design used in each test was randomized blocks, the treatments were: ten genotypes in two levels of phosphorus and three replications.
 Place and Duration of Study: Sítio Vitória, municipality of Santa Maria das Barreiras, state of Pará, Brazil, in the 2017/18 crop.
 Methodology: The experimental plot consisted of four lines five meters long, spaced with 0.90 m between the lines, with approximately 55,000 plants per hectare in the harvest. The genotypes used: 2B655, AG 1051, AG 8088, AL BANDEIRANTE, ANHEMBI, BR 206, BRS 3046, CATIVERDE, ORION e PR 27D28. The following agronomic characteristics were evaluated: plant height, ear height, ear diameter, ear length, number of grains per row, yield per plant and grain yield. Genetic divergence was estimated from Mahalanobis distances and genotypes were grouped by Tocher optimization methods.
 Results: Genetic dissimilarity measurements, at each dose of phosphorus, showed a high magnitude (D2= 9.72 to 1484.87). Cluster analysis separated the genotypes into four groups at low phosphorus and two groups at high phosphorus. The characteristics that most contributed to genetic divergence, in the two levels of phosphorus, were yield per plant and grain yield.
 Conclusion: There was a higher genetic divergence between genotypes AG 1051 and BANDEIRANTE in the low phosphorus assay and between the genotypes ANHEMBI and AL BANDEIRANTE in the high phosphorus assay. With this, these crosses are promising to obtain lineages in both tests.

Image phenotyping of lettuce germplasm with genetically diverse carotenoid levels

ABSTRACT Developing biofortified foods such as lettuce is a frequent goal of breeding programs. One obstacle to the success of these efforts is the high temporal and financial cost of determining leaf constituents. Image phenotyping has been increasingly used in crop breeding, but not in lettuce breeding. Until now, the use of image phenotyping to indirectly select carotenoid-rich lettuce inbred lines has not been reported. Therefore, the goal of this study was to use image phenotyping to select lettuce inbred lines with different carotenoid levels. Twenty-two inbred lettuce lines, resulting from the hybridization of the cultivars Pira 72 and Uberlândia 10000 and six successive selfings were evaluated. ‘Grand Rapids’, ‘UFU-Biofort’ and ‘Uberlândia 10000’ were used as controls. The following variables were evaluated: agronomic potential, apparent genetic diversity and image phenotyping. The data were submitted to the ANOVA F test (p ≤ 0.05) and means compared by the Scott–Knott test (p ≤ 0.05). Genetic divergence was represented by dendrograms constructed by UPGMA and the Tocher optimization method. The relative contribution of characters was assessed to identify the most relevant response variable. The genetic diversity of the evaluated germplasm bank was the greatest regarding soil plant analysis development (SPAD)/carotenoid values. Image phenotyping was successfully used to detect different levels of SPAD/carotenoid levels and could be a useful tool for plant breeding. The results of this study can be used to predict the nutritional values of the carotenoid content in lettuce leaves before commercialization.

Genetic diversity between native cupuízeiros from Portal da Amazonia, Mato Grosso, Brazil

Theobroma subincanum Mart. popularly known as cupuí, belongs to the family Malvaceae. It is a wild fruit species native to the Amazon and is found in mainland forests, being characterized by its great alimentary and ecological importance. The cupuí presents genes that can be used for the croop breeding of commercial species of the genus, so that many studies have been carried to characterize genotypes through molecular markers, among which ISSRs (Inter Simple Sequence Repeats) have been widely used. In this context the objective of the study was to analyze the genetic diversity among cupuí genotypes, using molecular markers ISSR. Ten markers used amplified 42 fragments, being 35.71% polymorphic, and the genetic dissimilarity, estimated from the Jaccard coefficient, varied from 0.02 to 0.26, indicating the existence of genetic variability among the studied genotypes. The UPGMA grouping method allocated the twenty genotypes of cupuí analyzed in three groups, while the Tocher optimization method distributed the same in eight groups, thus confirming the existence of genetic diversity among the evaluated materials. The two methods of grouping revealed that the MN08, MN09 and MN10 individuals are the most divergent and therefore the most suitable for conservation and breeding programs of the species.

GENETIC DIVERSITY OF BRAZILIAN PEPPER BASED ON QUALITATIVE REPRODUCTIVE TRAITS

In Brazil, pepper cultivation gives producers more marketing opportunities in various segments, either for fresh consumption or industry. Reproductive traits are efficient methods for comparing genetic divergence in pepper, once most differences among accessions could be verified at this stage. This study aimed to evaluate the genetic divergence in the reproductive phase of pepper accessions by multivariate analysis and test the efficiency of different methods. Sixty-five genotypes from the Federal University of UberlândiaCapsicum spp. Germplasm Bank were evaluated 145 days after sowing, and morphological characterization was performed at reproductive phase. Graphical representation of genetic distances was obtained by UPGMA. Tocher optimization method was also used to group accessions. Genotypes were arranged in seventeen different groups by Tocher method. UPGMA dendrogram collaborated with Tocher method, indicating the wide genetic variability of genotypes. Tocher and UPGMA methods were partially in agreement, allowing grouping 44 of the 65 analyzed accessionsequally. Multicategorical traits have the advantage of easy observation and require less time and labor, being ideal for use in gene bank and collections that do not have high human and financial resources. Moreover, these traits are not affected by the environment. Genetic divergence detected in this paper encourages other researchers to perform the characterization of pepper collections as completely as possible, because it becomes possible to generate more reliable information of the variability and genetic divergence among accessions. Our research discloses the reproductive biodiversity of pepper in “Alto Paranaíba” and “TriânguloMineiro” regions and the importance of maintaining these genotypes.

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.

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.