Evolution and improvement of cultivated amaranths IX. Cytogenetic relationship between the two basic chromosome numbers

Abstract

The relationship between the two basic numbers (n = 16 and n = 17) in the grain group of species of the genus Amaranthus was determined through an interspecific dibasic cross involving white seeded cultivated A. hypochondriacus (n = 16) and black seeded wild A. hybridus (n =17, African). In the hybrid at metaphase I 98 percent of pollen mother cells had 15 bivalents + 1 trivalent; the remaining cells had 16 bivalents + 1 univalent. Chromosome counts in the 55 hybrid plants revealed the distribution of plants with 2n = 32, 33, and 34 in the ratio of 1:2:1, respectively. The origin of n = 17 from n = 16 through primary trisomy is suggested.