EFFECTS OF ABSCISIC-ACID ON WHEAT CALLUS-CULTURES

In tissue culture, use of various plant growth regulators has been sho wn to modify callus growth and plant regeneration rates. This study ex amined the effects of 0.5, 1.0, 1.5 and 2.0 mu M concentrations and tw o modes of application of abscisic acid (ABA), namely in the medium an d topical application, on callus growth and plant regeneration of two wheat (Triticum aestivum L.) genotypes, PI 137739 and 'Stephens'. Call us induction and proliferation were arrested by ABA treatments in the first month. Enhanced growth of up to 3-fold was observed in ABA treat ed calli compared to control when they were transferred to maintenance medium without ABA in the second month. In 'Stephens', increased plan tlet production was observed when ABA was incorporated in the medium. Thus, wheat genotypes responded differently to ABA treatments with reg ards to calli growth and plant regeneration capability.