Quinoa cultivars currently grown in North America and Europe require removal of 
bitter-tasting saponins from the grain prior to human consumption. This need for 
postharvest processing is a barrier to expanding production of the crop outside 
its Andean area of origin. Grain saponin content in quinoa shows continuous 
variation and is considered to be a quantitative trait. However, segregation for 
the presence or absence of grain saponin in F2 generations derived from crosses 
between high- and low-saponin parents indicates a major gene effect, with plants 
homozygous for a recessive allele spl having no detectable grain saponin. 
Variation in saponin levels among F2 plants with detectable grain saponin was 
consistent with polygenic inheritance. It appears that grain saponin level in 
quinoa is both qualitatively and quantitatively controlled, with saponin 
production requiring at least one dominant allele at the Sp locus and the amount 
of grain saponin being determined by an unknown number of additional 
quantitative loci. Introgression of sp1 into day-neutral lines will facilitate 
the development of short-season "sweet" quinoa cultivars which do not require 
postharvest processing to remove grain saponin.