Estimativas de parâmetros genéticos para caracteres de cenoura em sistemas de cultivo agroecológico

AUTOR(ES)
DATA DE PUBLICAÇÃO

2008

RESUMO

The aim of the present work was to estimate genetic parameters that provide the definition of a breeding strategy, looking for the development of new varieties of carrot adapted to the conditions of Distrito Federal agroecologic cultivation. Considering data from tests in areas of agroecologic cultivation (Natural Agriculture - AN and Organic Agriculture - AO) in Distrito Federal, the following characteristics were evaluated: incidence of leaf blight (QDF), incidence of root cracking (RACH), root length (COMP), root diameter (DR), root mass (MASSA), xylem diameter (DX), relation of xylem diameter / root diameter (DX/DR), format of root tip (TP), format of root shoulder (TO), measure of the color of the a* xylem parameter (a*X), measure of the color of the a* phloem parameter (a*F). Traits were evaluated in 100 half-sib progenies derived from Brasília cultivar, using a complete randomized block design. The values of the variance analysis for treatment X environment interactions were not significant to the characters DR, MASS, DX and DX/DR. For the characters COMP, a*X, a*F, TP and TO, the treatment X environment interaction was significant by test F. The values of the individual variance analyses, for the characters that showed significant interaction in treatment X environment variance analysis, presented significant effect for the characters COMP, a*X, TP, TO, QDF for AN system and COMP, a*X, a*F, TP for AO system. In AN system, the values of the heritability estimates (ha) for plant characters COMP, a*X, a*F, QDF, RACH were: 65.66, 37.05, 8.26, 39.11, 25.52%, respectively. The reason (CVg / CVe) was less than 1 for all characters evaluated in AN system. The values of the heritability estimates (ha) for AO system of the characters COMP, a*X and a*F were 53.00, 81.13 and 49.02%, respectively. The reason (CVg / CVe) for the characters a*X and TP showed values greater than 1 in AO system. About phenotypic and genotypic values of correlations, it was observed that for most characters, the values of genotypic correlation were higher than those found in phenotypic correlation. It was possible to verify that the characters a*X and a*F correlated positively with each other in the two agroecologic cropping systems AN and AO. It was also found that the value of a*X is lower when root diameter is larger, and because of this, larger root diameters gives less amount of carotene in the xylem of carrot roots. The phenotypic and genotypic correlations between the characters DR and QDF in AN system were rf = 0,23; rg = 0, 56, respectively. Moreover, it was observed that the incidence of root crack is lower when root length is higher. Estimates of genetic gain per cycle for the characters a*X and a*F were lower in AN system than the estimates observed in AO system. Estimates of genetic gain obtained in both agroecology cropping systems for the character COMP were similar. In accordance with preliminary information available, is suggested the installation of essays in one place only, since the characteristics which have close relation with root productivity (mass, root diameter, xylem diameter and the relation of xylem diameter / root diameter), showed stable performance of the genotypes evaluated in the different systems. In accordance with these results, is suggested that the process of carrot breeding for leaf blight in organic systems should be made in conventional systems in which strategies to maximize the efficiency of the selection process can be used.

ASSUNTO(S)

genetic gain agroecologia heritability correlações correlations agroecology daucus carota l. daucus carota ganho genético herdabilidade ciencias agrarias

ACESSO AO ARTIGO

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