Occurrence of sapogenins in leaves and seeds of quinoa (Chenopodium quinoa Willd)

Seeds of the Andean seed crop quinoa usually contain saponins in the seed coat. Saponins give a bitter taste sensation and are a serious antinutritional factor. Therefore selection of sweet genotypes with a very low saponin content in the seeds is a main breeding goal. However, selection for sweet genotypes is retarded by cross-pollination. Early identification of sweet and bitter quinoa genotypes before anthesis would speed up breeding considerably. The ability to distinguish sweet and bitter genotypes was investigated in a glasshouse and in a field experiment. In the glasshouse experiment the content of sapogenins was determined in leaves of sweet and bitter quinoa genotypes at successive stages of plant development and finally in the seeds. Detectable amounts of sapogenins were found earliest 82 days after sowing in leaves of both sweet and bitter quinoa genotypes. The total sapogenin content in leaves of sweet and bitter genotypes increased during plant development but remained lower than the content found in the seeds. The sapogenin content in seeds of sweet genotypes varied from 0.2 to 0.4 g kg(-1) dry matter and in seeds of bitter genotypes from 4.7 to 11.3 g kg(-1) dry matter. The difference in sapogenin content between leaves and seeds was much higher in bitter genotypes than in sweet genotypes. Hederagenin was the major sapogenin found in leaves, and oleanolic acid in seeds. In the field experiment it was found that the content of sapogenins in the leaves of F2 plants of crosses between both quinoa types did not differ between sweet and bitter genotypes. The obtained results demonstrated that sweet genotypes could not be selected before anthesis on the basis of the sapogenin content in the leaves. (C) 2000 Society of Chemical Industry.