Variability of maize genotypes for grain-carotenoid composition aiming biofortification / Variabilidade de genótipos de milho quanto à composição de carotenóides nos grãos visando a biofortificação

AUTOR(ES)
DATA DE PUBLICAÇÃO

2007

RESUMO

Vitamin A deficiency is the leading cause of blindness in the world, reaching approximately 21% of all the mal nourished children, with the largest number of affected kids in parts of Asia and Africa. Biofortification of the maize with provitamin A carotenoids, through breeding, is an alternative to diminish this deficiency, mainly in poor countries. The maize grain is one of main staple food in poor areas reached by hipovitaminose A. Maize possess carotenoids with variability in content and profile, what makes breeding a possibility. Carotenoids are liposoluble compounds found in plants, microorganisms and some animals, and of the 600 existing types, about 50 carotenoids possess provitamin A activity. Of these substances, the β-carotene, is the main target for genetic improvement. The objective of this work was the characterization of 134 maize genotypes for carotenoids content and profile. All seeds came from the experimental fields and the Active Gene Bank of Embrapa Milho and Sorgo, at Sete Lagoas, MG, Brazil. The genotypes were commercial hybrids and varieties from national trials, inbred lines developed by the Embrapa biofortification breeding program and other accesses chosen due its yellow-orange endosperm color. The analyses were carried out in duplicates by spectrophotometric method to quantify the content of total carotenoids, carotenes, monohidroxylados and xanthophylls. The variations for the following traits: total carotenoids (9.46 to 42.84 μg/g), carotenes (0.88 to 4.93 μg/g), xanthophylls monohidroxylated (1.13 to 7.22 μg/g) and xanthophylls diidroxylated (5.55 to 34.11 μg/g). The average total carotenoid was 22.34 μg/g and the inbred line 541332 averaged 42.84 μg/g. Carotene average was of 2.66 g/g, being the largest concentration found for BRS 1001 (4.93 g/g); the materials analyzed averaged monohidroxylated and xanthophylls levels of 3.88 and 16.93 gμ/g, respectively, with prominence for two elite inbreds, 540755 with 7.22 μg/g of monohidroxylated and 541312-1 with 34.11 μg/g of xanthophylls. Comparing these results to ordinary averages it can be observed that the Embrapa germplasma has good variability and high potential for development of biofortified lines, mainly for total of carotenoids provitamin A. By multivariate analysis, the genotypes were grouped by the Tocher method in 18 groups, having as dissimilarity measure the average Euclidian distance. However, there are great genetic similarities among the entries. For selection of genotypes for genetic improvement, the materials were chosen for greater content of total carotenoids and carotenes and those of divergent groups shown in the Tocher grouping. In addition, for each genotype was established using the ratio monohidroxylated/carotenes and xanthophylls/monohidroxylated, two indices, to indicate tendencies to produce monohidroxilados and xanthophylls. Thus, four ideotypes were established taking in consideration the lower indices, higher contents of total carotenoids and also higher proportion of carotenes. These four ideotypes were included with the 134 genotypes for generation of a dendrogram, by the clustering method Ward. In the dendrogram was identified genotypes clustered with the ideotypes, which were selected as promising entries a biofortification breeding program. Finally, 20 elite inbred lines were also identified for breeding for provitamin A content.

ASSUNTO(S)

fitotecnia vitamin a milho maize carotenoid biofortification carotenóides vitamina a biofortificação

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