Multivariate techniques for the study of genetic diversity

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.

The genotypes evaluation in a germplasm bank is essential to determine their commercial or usefulness, as potential parents, in a breeding program. We aimed to detect the genetic diversity of 42 tomato genotypes of cherry type, belonging to the germplasm bank of the Federal University of Uberlândia and, also evaluate their behavior. The experiment was conducted in a greenhouse in randomized block design with 42 treatments and two replications. Ten quantitative traits of agronomic importance were evaluated. The genetic divergence was obtained by multivariate analysis, using the Mahalanobis distance with different clustering methods (UPGMA and Tocher). The hybrids performance was compared by Scott-Knott (p=0.05) and Dunnett’s test (p= 0.05). UPGMA and Tocher grouped the genotypes similarly, representing genetic divergence satisfactorily. The genotypes UFU 29, UFU 21 and UFU 07 were more productive, earlier and also divergent from the pre-commercial treatment (UFU 200), being able to be used as potential parents.

Evaluation of pre-commercial hybrids in a germplasm bank is essential for determining its commercial potential or its utility as a potential genitor in a breeding program. The objective of this study was to determine genetic divergence and per se behavior of 47 pre-commercial hybrids from okra germplasm bank of the Universidade Federal de Uberlândia. Precocity index (%), number of fruits (fruits per plant), average fruit mass (g) and productivity (g per plant) were evaluated. Analysis of genetic divergence was performed by multivariate analysis using Mahalanobis distance with different clustering methods (UPGMA and canonical analysis). The performance of hybrids was compared by Scott-Knott (p= 0.05). A significant genetic variability among okra hybrids was observed. UPGMA and canonical analysis grouped the hybrids similarly, being satisfactory to represent genetic divergence. Ten hybrids presented higher performance than the commercial hybrids. Among them, UFU-QB16 stood out as the most promising hybrid for being used as a potential parent in breeding programs after auto pollination. Keywords: Abelmoschus esculentus; genetic variability; heterosis

This study aimed evaluating the genetic divergence of vegetative stage in pepper access by means of multivariate analysis and testing the efficiency of different methods. In order to reach this goal 65 accessions from the Germplasm Bank of Capsicum spp of the Federal University of Uberlândia-Brazil were evaluated concerning the following qualitative characteristics: presence of nodal anthocyanin, shape of the stem, presence of trichomes on the plant, branching habit, coloring of the leaves, leaf shape, pubescence of the leaves and leaf margin. The quantitative characteristics such as length and width of leaves were also evaluated. Qualitative characters were grouped as multi-categorical variables and the dissimilarity matrix was calculated based on the Cole-Rogers distance. As for quantitative traits, the dissimilarity matrix was measured by Euclidean distance average. Matrices were added in order to apply the clustering methods approach. Three clustering techniques were applied: Tocher optimization method, UPGMA and principal component analysis. Average and mode of the groups generated were also calculated. Validation of Tocher and UPGMA clusters was determined by cophenetic correlation coefficient. There was divergence among the accessions evaluated. UPGMA methods, Tocher and principal components were efficient and converged in the identification of distinct groups regarding the vegetative phase of pepper access. RESUMO: Comparação de métodos de agrupamento no estuda da diversidade genética em acessos de pimenta na fase vegetativa. O presente trabalho teve como objetivo avaliar a divergência genética na fase vegetativa em acessos de pimenta por meio de análise multivariada e testar a eficiência de diferentes métodos. Foram avaliados 65 acessos pertencentes ao Banco de Germoplasma de Capsicum spp da Universidade Federal de Uberlândia-Brasil. Avaliou-se as seguintes características qualitativas: presença de antocianina nodal, formato da haste, presença de tricomas na planta, hábito de ramificação, coloração das folhas, forma da folha, pubescência nas folhas, margem da folha, além de características quantitativas como comprimento e largura das folhas. Os caracteres qualitativos foram agrupados como variáveis multicategóricas e a matriz de dissimilaridade foi calculada pela distância de Cole-Rodgers. Para os caracteres quantitativos, a matriz de dissimilaridade foi mensurada pela distância euclidiana média. As matrizes foram somadas para a aplicação dos métodos de agrupamento. Foram realizadas três técnicas de agrupamento aos acessos: método de otimização de Tocher, UPGMA e análise de componentes principais. A média e moda dos grupos formados foram também calculadas. O coeficiente de correlação cofenético foi determinado para validação dos agrupamentos de Tocher e UPGMA. Houve divergência genética entre os acessos avaliados. Os métodos de agrupamento UPGMA, Tocher e componentes principais foram eficientes e convergentes na identificação de grupos distintos na fase vegetativa de acessos de pimenta.