Inheritance of Nitrogen Use Efficiency in Inbred Progenies of Tropical Maize Based on Multivariate Diallel Analysis

The objective of our study was to characterize and determine the patterns of genetic control in relation to tolerance and efficiency of nitrogen use by means of a complete diallel cross involving contrasting inbred progenies of tropical maize based on a univariate approach within the perspective of a multivariate mixed model. Eleven progenies, previously classified regarding the tolerance and responsiveness to nitrogen, were crossed in a complete diallel cross. Fifty-five hybrids were obtained. The hybrids and the progenies were evaluated at two different nitrogen levels, in two locations. The grain yield was measured as well as its yield components. The heritability values between the higher and lower nitrogen input environment did not differ among themselves. It was observed that the general combining ability values were similar for both approaches univariate and multivariate, when it was analyzed within each location and nitrogen level. The estimate of variance of the specific combining ability was higher than general combining ability estimate and the ratio between them was 0.54. The univariate and multivariate approaches are equivalent in experiments with good precision and high heritability. The nonadditive genetic effects exhibit greater quantities than the additive genetic effects for the genetic control of nitrogen use efficiency

Associação entre caracteres dos tubérculos de batata em gerações iniciais de seleção sob condições contrastantes de temperatura

A eliminação de genótipos indesejáveis nas gerações iniciais de seleção proporciona economia de recursos nos programas de melhoramento. A correlação é uma ferramenta que auxilia na seleção precoce, ou na seleção indireta, através de caracteres correlacionados. O objetivo deste trabalho foi estimar a correlação entre os caracteres de aparência, produção e peso específico dos tubérculos, e avaliar a viabilidade da seleção precoce. Os experimentos foram realizados em casa de vegetação e em campo, sendo utilizadas famílias clonais oriundas de um dialelo parcial entre cultivares de boa aparência de tubérculos e clones tolerantes ao calor. Foram avaliados produtividade; peso específico e caracteres de aparência dos tubérculos; e, estimada a correlação entre os caracteres e entre as gerações. O formato dos tubérculos foi o caráter que apresentou maior correlação entre as gerações. Verificou-se forte correlação entre o formato dos tubérculos e defeitos como apontamento e curvatura, na primeira e segunda geração clonal conduzidas em campo. Para produtividade e peso específico dos tubérculos constatou-se boa correlação entre os experimentos conduzidos em casa de vegetação. Concluiu-se que a seleção precoce é eficiente para formato de tubérculos na geração de seedling; e, na primeira geração clonal, para formato de tubérculos, profundidade de olhos, e contra os defeitos apontamento e curvatura dos tubérculos

Escalas diagramáticas para avaliação do fenótipo de tubérculos de batata

Nos programas de melhoramento de batata existem diversos caráteres dos tubérculos que são avaliados com o auxílio de escalas diagramáticas. Entretanto, não há padronização das escalas entre os programas de melhoramento, fazendo com que cada programa adote a sua própria escala. O objetivo do trabalho foi elaborar e validar diferentes escalas diagramáticas para avaliação de caracteres relacionados ao fenótipo de tubérculos de batata. Foram considerados os caracteres: textura da periderme; formato; profundidade de olhos; coloração de polpa; coloração de palito após a fritura; coloração de “chips” após a fritura e coloração de pele. Dez avaliadores atribuíram notas aos tubérculos para os caracteres sem e com o uso das escalas. Foram avaliadas dez repetições classificadas em cada nota da respectiva escala utilizando o delineamento inteiramente casualizado. Os dados de todos avaliadores foram submetidos à análise de regressão linear entre as notas reais e as médias das notas dos avaliadores sem e com o uso da escala. Quando a avaliação foi realizada com o uso das escalas, todos os avaliadores melhoraram sua precisão, com aumento nos coeficientes de determinação para todos os caracteres estudados. Essas escalas apresentam-se como uma ferramenta bastante oportuna para auxiliar nas avaliações dos caracteres que compõe a aparência geral dos tubérculos, haja vista a falta de um sistema padrão de avaliação

Evaluating the impact of modeling the family effect for clonal selection in potato-breeding programs

Because of its wide distribution, high yield potential, and short cycle, the potato has become essential for global food security. However, the complexity of tetrasomic inheritance, the high level of heterozygosity of the parents, the low multiplication rate of tubers, and the genotype-by-environment interactions impose severe challenges on tetraploid potato–breeding programs. The initial stages of selection take place in experiments with low selection accuracy for many of the quantitative traits of interest, for example, tuber yield. The goal of this study was to investigate the contribution of incorporating a family effect in the estimation of the total genotypic effect and selection of clones in the initial stage of a potato-breeding program. The evaluation included single trials (STs) and multi-environment trials (METs). A total of 1,280 clones from 67 full-sib families from the potato-breeding program at Universidade Federal de Lavras were evaluated for the traits total tuber yield and specific gravity. These clones were distributed in six evaluated trials that varied according to the heat stress level: without heat stress, moderate heat stress, and high heat stress. To verify the importance of the family effect, models with and without the family effect were compared for the analysis of ST and MET data for both traits. The models that included the family effect were better adjusted in the ST and MET data analyses for both traits, except when the family effect was not significant. Furthermore, the inclusion of the family effect increased the selective efficiency of clones in both ST and MET analyses via an increase in the accuracy of the total genotypic value. These same models also allowed the prediction of clone effects more realistically, as the variance components associated with family and clone effects within a family were not confounded. Thus, clonal selection based on the total genotypic value, combining the effects of family and clones within a family, proved to be a good alternative for potato-breeding programs that can accommodate the logistic and data tracking required in the breeding program

FRUIT MORPHOLOGY AND PRODUCTIVITY OF BABASSU PALMS IN NORTHERN MINAS GERAIS STATE, BRAZIL1

ABSTRACT The objectives of this study were to morphologically characterize fruits of the babassu palm tree (Attalea vitrivir) and to estimate their productivity in the north of Minas Gerais State, Brazil. Twenty mature fruits were collected from 10 plants in three different areas in Januária, Minas Gerais. Eighteen biometric parameters of the fruits were measured, the oil contents of the seeds was determined, the adherence to normal distribution was evaluated, distribution frequencies were evaluated and the effects of individuals and areas on the variables and the correlations between them were analyzed. The production of fruit bunches per plant and the number of fruits per bunch from 10 plants were quantified in three areas and the potential production under both natural harvesting and cultivation conditions were estimated. Significant differences were found among all of the biometric parameters examined between the different individuals and the different areas, which shows wide morphological variability in the fruits. The average oil content was 45.7%, but with significant differences among individuals. The observed variability favors the selection of productive individuals in genetic improvement programs. The potential productivity of endocarps and oil based on a density of 400/plants per hectare would be respectively 6.4 and 1.2 tons/ha, which indicates the possibility of using A. vitrivir for producing charcoal, bio fuels, and for carbon fixation