[Genetic variability and correlation of yield, grain size, chemical composition and protein quality of 25 varieties of amaranth (Amaranthus caudatus)].

The purpose of the present research was to establish the variability in agronomic, chemical and nutritional characteristics among 25 amaranth (A. caudatus) cultivars. A large variability was found among cultivars in all the parameters evaluated. Average seed weight was 0.75 mg, and had an average size of 1.23 x 1.14 mm. The average moisture, protein and fat content was 11.81, 12.66 and 8.44%, respectively. The average values for methionine, threonine, cystine, leucine and lysine were: 168, 276, 74, 381 and 370 mg/g N, in the same order as presented. It was possible to establish significant, positive correlations between yield-protein, methionine-cystine, methionine-lysine, and threonine-leucine, as well as significant negative correlations between protein-cystine, fat-methionine and cystine- leucine. Furthermore, it is not possible to select cultivars of higher yield on the basis of seed weight, since these two variables were negatively correlated, although not statistically significant. Among all 25 cultivars studied, some were deficient in sulfur-containing amino acids, while based on the FAO/WHO essential amino acid pattern, all of them were deficient in leucine. The average protein quality value expressed as NPR was 3.54 in thermally-processed samples, with no differences between cultivars. Nevertheless, protein digestibility values probably classified the samples in two groups with average values of 79 and 81%, respectively. The variability found can thus be used to select cultivars with higher yields and higher nutritional characteristics.