Correlation study of resistance components in the selection of Capsicum genotypes resistant to the fungus Colletotrichum gloeosporioides.

Anthracnose is among the major diseases of the Capsicum culture. It is caused by different species of the genus Colletotrichum, which may result in major damages to the cultivation of this genus. Studies aiming to search for cultivars resistant to diseases are essential to reduce financial and agricultural losses. The objective of this study was to evaluate the correlation between the variables analyzed to select Capsicum genotypes resistant to the fungus Colletotrichum gloeosporioides. The experimental design was completely randomized blocks with three replications, 88 treatments, four ripe fruits, and four unripe fruits per replication. Accessions of Capsicum from the Germplasm Active Bank of Universidade do Estado de Mato Grosso (UNEMAT) were evaluated as for resistance to the fungus. Fruits were collected from each plot and taken to the laboratory for disinfestation. A lesion was performed in the middle region of the fruit using a sterile needle, where a spore suspension drop, adjusted to 106 spores/mL, was deposited. An ultrapure water drop was deposited into control fruits. The fruits were placed in humid chambers, and the evaluation was performed by measuring the diameter and the length of lesions using a caliper for 11 days. After data were obtained, analyses of variance, correlation, and path analysis were performed using the GENES software and R. According to the likelihood-ratio test, the effects of genotypes (G), fruit stage (F), and its interaction (G x F) were significant (P < 0.05). There were differences between the magnitudes of genotype correlations according to fruit stage. Different variables must be taken into account for an indirect selection in this culture in function of fruit stage since the variable AUDPC is an important criterion for selecting resistant accessions. We found through the path analysis that the variables DULRD and DULRL exerted the greatest effects on AUDPC.

Morphological diversity of cassava accessions of the south-central mesoregion of the State of Mato Grosso, Brazil.

Genetic variability of cassava (Manihot esculenta Crantz) in Brazil is wide, being this the result of natural and cultural selection during pre- and post-domestication of the species in different environments. Given the number of species of the genus found in the region (38 of a total of 98 species), the central region of Brazil was defined as the primary center of cassava diversity. Therefore, genetic diversity characterization of cassava accessions is fundamental, both for farmers and for plant breeders, because it allows the organization of genetic resources and better utilization of available genetic diversity. This research aims to assess genetic divergence of cassava accessions from the south-central region of the State of Mato Grosso, based on multi-categorical morphological traits. For this purpose, 38 qualitative and quantitative morphological descriptors were used. Genetic diversity was expressed by the genetic similarity index, with subsequent clustering of accessions by the modified Tocher's procedure and UPGMA. Of 38 descriptors, only growth habit of stem showed no variability. Tocher and UPGMA methods were efficient and corroborated on group composition. Both methods were able to group accessions of different localities in distinct group consistency.

Morphological descriptors and ISSR molecular markers in the evaluation of genetic variability of Tectona grandis genotypes.

This study aimed to evaluate the genetic variability of the teak germplasm bank, using morphological traits and inter-simple sequence repeat molecular markers. Thirty clones were evaluated in a randomized complete block design with three replicates, and each plot was composed of three plants. A joint analysis of quantitative and qualitative variables was performed using the Gower algorithm. Quantitative, qualitative, and molecular variables were analyzed simultaneously using the Ward-MLM procedure. There is genetic variability among the 30 teak genotypes studied, considering the quantitative, qualitative, and molecular variables by the Ward-MLM statistical procedure. Morphological traits used proved to be efficient for the study of genetic variability; however, it was not possible to compose a descriptor table for clonal teak genotypes based on the traits evaluated. The Gower method was efficient in discriminating the groups, demonstrating that the simultaneous analysis of qualitative and quantitative data is feasible and can allow greater efficiency in the knowledge of the variability among teak genotypes. The genotype 22 showed to be the most divergent compared to the other genotypes, except for the cluster of genotypes by the UPGMA method based on the Gower distance obtained by the Ward-MLM procedure, which formed a group with genotypes 9 and 30, in the morphological and molecular analyses and was grouped alone.

Correlation and path analysis of biomass sorghum production.

Sorghum biomass is an interesting raw material for bioenergy production due to its versatility, potential of being a renewable energy source, and low-cost of production. The objective of this study was to evaluate the genetic variability of biomass sorghum genotypes and to estimate genotypic, phenotypic, and environmental correlations, and direct and indirect effects of seven agronomic traits through path analysis. Thirty-four biomass sorghum genotypes and two forage sorghum genotypes were cultivated in a randomized block design with three replicates. The following morpho-agronomic traits were evaluated: flowering date, stem diameter, number of stems, plant height, number of leaves, green mass production, and dry matter production. There were significant differences at the 1% level for all traits. The highest genotypic correlation was found between the traits green mass production and dry matter production. The path analysis demonstrated that green mass production and number of leaves can assist in the selection of dry matter production.