Ability of Callus Induction and Plant Regeneration in White Kashan and Red Rey Onions Cultivars (Allium cepa L.) Using Root - tip Culture under Invitro Conditions

This present study has been carried out in order to evaluate the effect of culture medium and genotype on callus induction and regeneration of two onion varieties through root tip culture. For callus induction, micro samples from 1-3 mm root tip of 2 day old in vitro germinated plants laied on four culture media (1mg/l 2, 4-D, 0/5mg/l 2, 4-D, 0/5mg/l 2, 4-D with 0/5mg/l kinetin, 1mg/l 2,4-D with 1mg/l kinetin) in darkness conditions. Subculture of samples was done after four weeks. The  produced calluses were laied in embryogenic culture medium for 4 weeks and after formation of embryoes, they were put in plant regeneration culture medium for eight weeks. Result showed that callus induction percentage is affected significantly by cultivar and culture medium, but reciprocal effect of both factors was not meaningful on callus induction percentage. Plant regeneration percentage and number of embryo per callus is affected meaningfully by cultivar, but type of culture medium and reciprocal effect of both factors was not meaningful on plant regeneration percentage and number of embryoes per callus. Embryogenic callus percentage is affected meaningfully by cultivar, but type of culture medium had not meaningful effect on embryogenic callus percentage. Callus induction percentage, plant regeneration percentage, number of embryo per callus and embryogenic callus percentage, are higher in white Kashan cultivar in relation to red Rey one and in culture medium involving hormonal combination of 2,4-D and kinetin, application of 0/5mg/l 2, 4-D can be usful. Considering the callus induction percentage, embryogenic and plant regeneration percentage, white Kashan cultivar and  culture medium containing 0/5mg/l 2, 4-D is appropriate as compared with other cultures