Evolution and improvement of cultivated amaranths : VII. Cytogenetic relationships in vegetable amaranths.

Of the four interspecific hybrids, three (A. graecizans var. graecizans X A. tricolor cv. 'Purple leaf', A. lividus var. lividus X A. tricolor var. viridis and A. gracilis X A. tricolor cv. 'Purple leaf') were studied cytologically. In all the three, differentiation between the parents is chiefly a result of interchanges and paracentric inversions. The interchange complexes may involve from four (A. gracilis X A. tricolor cv. 'Purple leaf') to fourteen (A. lividus var. lividus X A. tricolor var. viridis) chromosomes, indicating that the parents differ from each other in 1 to 6 interchanges. Because of the small size of the chromosomes, it is possible that crossing-over in interchange for small segments is restricted. The particular parental species representing the ancestral condition from which others were derived or compounded is difficult to pin-point. With preferential pairing and the restoration of fertility in the amphidiploid A. lividus-tricolor, it became clear that it is very likely that the interchanged segments are small and sterility in the hybrid is entirely chromosomal.This situation is in strong contrast to that in Sect. Amaranthus, where the single male flower per glomerule and huge showy inflorescences lead to more cross-pollination; coupled with this are strong morphological divergences between taxa and less genetic differentiation. In the Sect. Blitopsis, there are a number of male flowers per glomerule and small non-showy axillary inflorescences, leading to self-pollination, and less morphological but strong genetic differentiation by interchanges and inversions.