Elucidating the ethylene response and tolerance in non-mutagenized and mutagenized snapdragon (Antirrhinum majus L.) lines using 1-aminocyclopropane-1-carboxylic acid (ACC)

A tissue culture screen for ethylene tolerance utilizing 1-aminocyclopropane-1-carboxylic acid (ACC) was optimized for Antirrhinum majus L. (snapdragon) inbred line OAK564. The influence of various concentrations of ACC, including 0, 0.25, 0.50, 1.0, 2.5, 5.0, 10, 25, 50, 75, and 100 µM on seedling growth was investigated. It was determined that 5 µM ACC was optimum in elucidating biological activity. This screen was then used to evaluate responses of 48 snapdragon hybrid lines along with an inbred line to ethylene based on hypocotyl elongation inhibition. Moreover, 40,000 mutagenized snapdragon seeds from three M₂ populations, derived from ethyl methanesulfonate (EMS) treatments of 0.50, 0.75, and 1.0%, were also assessed for ethylene insensitivity based on presence/absence of an ethylene ‘triple response’. From this ethylene screen, a total of 231 putative ethylene mutants were recovered, exhibiting eight distinct phenotypes corresponding to the ‘triple response’. Of these, 16 mutants were selected for further analysis that included at least one and up to three lines from each of the eight identified phenotypic groups. M₂ plants were grown in the greenhouse, and selfed seeds were collected. These M₃ seeds were then screened with 5 µM ACC to assess their tolerance to ethylene at the population level. Responses varied from complete ethylene tolerance to ethylene sensitivity among the different putative mutant lines.