Genetics of Time of Internode Elongation and Duration of Rosette Habit in Carthamus tinctorius L. and C. flavescens Spreng1

Abstract

Rosette habit is an important component in the length of the life cycle of safflower (Carthamus spp.). Rosette habit results from nonelongation of internodes. Segregating populations indicated that time of internode elongation, a measure of duration of rosette habit, was influenced by a major gene and modifier genes in C. tinctorius L. (cultivated safflower) and C. flavescens Spreng (an annual herbaceous weed, indigenous to the Middle East). All crosses showed that earliness of internode elongation had dominance, ranging from partial to over dominance. At threshold levels of expression, the frequency of rosette habit in some C. tinctorius genotypes changed with environments; however, the mean length of the first internode of these nonrosette plants was from 1/5 to 1/2 that of ‘Gila,’ which is noted for its nonrosette habit in a wide range of environments.