Intensive breeding and artificial selection of the desired traits in maize landraces through domestication have created modern maize, which needs a great technological contribution for optimal productive development. However, the narrowing of the genetic bases of maize made it difficult for traditional farmers to access productive genetic material that maintains the genotypic and phenotypic diversity capable of ensuring productive sustainability. Thus, objective of the study was to evaluate the variability and production gain in morphoagronomic characters of Nawa Sheki landraces maize after two mass selection cycles. The work was carried out in the experimental area of the Federal University of Acre, where two cycles of mass selection were applied on variety Nawa Sheki, in periods 2018/2019 and 2019/2020. The characteristics evaluated were: plant height, ear insertion height, ear length, ear diameter, number of rows of grains, number of grains per row, ear mass and grain mass. Data were submitted to descriptive analysis, with presentation of the histogram of frequency, asymmetry, kurtosis and Shapiro-Wilk test for the general population in both cycles. For the selected population, the following were obtained: mean, coefficient of variation, amplitude, minimum and maximum values and population variance in each cycle. The genetic parameters were selection differential for both cycles, production gain with selection and realized heritability of the first cycle. The choice of individuals in both cycles of mass selection was based on the ranking of the best values of the evaluated characteristics. The two cycles of mass selection provided high variability in the traits with the presence of superior phenotypes. Still, mass selection stabilized values for plant height, ear insertion height, followed by production gains for number of grains per row and ear mass.
Local varieties of cowpea are promising for breeding programs, as they harbor an important source of genetic variability. The objective of this study was to estimate the genetic variability among cowpea genotypes based on morphological and agronomic descriptors. The experiment was carried out in a randomized complete block design with three replications in the experimental field at Universidade Federal do Acre, in Rio Branco, Acre, Brazil. The experimental unit consisted of six lines of 5.0 m, with a spacing of 0.80 m x 0.50 m, with the four central lines used in the evaluations of 21 characters. The treatments consisted of seven local cowpea genotypes. The Mahalanobis generalized distances (D2) were calculated and used in the Tocher and UPGMA clusters. Principal component analysis, relative contribution of traits and analysis of variance were also performed. Manteiguinha and Mudubim de Rama were the most dissimilar genotypes, while Ceará Mercado and Baiano were the most similar. The main component of greater explanation illustrated the separation of genotypes into two groups, with the union between Manteiguinha and Manteigão forming one group and the other genotypes forming the other group. The traits grain yield, number of grains per pod and grain mass of fifty pods were the main determinants in the quantification of genetic divergence. The combination of the Manteiguinha with Mudubim de Rama genotypes is the most suitable for obtaining promising segregating populations.
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