The inheritance of flowering time inAmaranthus species

Abstract

The inheritance of flowering time was studied in a cross between an early flowering weedy species,Amaranthus retroftexus L., and a late flowering related crop species,A. cruentus L. Segregation ratios were scored in four successive backcrosses of the hybrid to the crop species (BC1 to BC4) and in backcross-derived generations (BC2F2, BC2F3) grown under 8-hr and 16-hr photoperiods and 30/20°C day/night temperatures in growth chambers, and under field and greenhouse environments during summer months at Davis. One major gene for earliness (Ea), dominant over late flowering, was identified conclusively under the 8-hr regime and in some genetic backgrounds under field conditions. Based on segregation patterns within individual progenies and the observed transgressive segregation, a model of three genes seemed to explain all of the ratios consistently. Evidence of segregation distortion at theEa locus, resulting in the deficiency of early individuals, and some role of epistatic interactions among the three postulated major genes requires further testing based on more isogenic and specific progeny materials. Flowering time was closely associated with plant form, inflorescence development, and numerous other traits which differentiate the crop and weed species. This association provides interesting insights into evolutionary changes under domestication and dispersal from lower to higher latitudes.