Variability of essential amino acid content in seeds of 22 Phaseolus species.

The reserve protein composition of 22 Phaseolus species has been studied. The non-sulphur-containing amino acids were present at values higher than those suggested for animal (and human) nutrition, but the sulphur-containing amino acids, with some exceptions, were under the minimum accepted requirement. However, taking into account the variability in the percentages of methionine and cystine, as well as the cystine/methionine ratio, it is concluded that the genus Phaseolus has a theoretical possibility for synthesizing a reserve protein with a balanced sulphur-containing amino acid content. An accession from Mexico of the species Ph. phyllanthus possesses a protein characterized by a high sulphur-containing amino acid content (3,84%). The possible utilization of this species in breeding for legume protein quality is suggested. Some observations about the percentage of arginine in wild and cultivated forms of Ph. Vulgaris are also presented.