Biomass Heterosis and Combining Ability in Interspecific and Intraspecific Matings of Grain Amaranths

To develop a practical foundation for breeding higher‐yielding grain amaranths (Amaranthus spp.), 32 amaranth accessions from the World Germplasm Collection were hybridized to produce 87 Fl's, which were subsequently evaluated for biomass heterosis and combining ability in three factorial mating designs. On average, interspecific matings of A. cruentus L. and A. hypochondriacus L., in comparison with their parents, produced highly significant (P < 0.01) biomass increases. When crossed with A. cruentus African vegetable accessions as females, male parents of both species showed significant (P ≤ 0.05) general combining ability (GCA). Mid‐parent heterosis for biomass ranged from −13 to 88% and high‐parent heterosis ranged from −24 to 40%. Late flowering of interspecific matings was associated with larger biomass yields. Preliminary experiments utilizing intraspecific matings within both A. hypochondriacus and A. cruentus gave no indication of high‐parent heterosis. Interspecific hybridization seems to be a promising way to increase biomass productivity of Amaranthus spp. for use as forage, energy feedstock, or a vegetable.