In vitro plant regeneration of Mammillaria elongata normal and cristate forms

In the normal form of Mammillaria elongata, shoots were regenerated in vitr o, through callus, from tubercle explants excised from the upper part of th e branch and cultured on Murashige and Skoog medium (MS) with 1.07 muM alph a -napthaleneacetic acid (NAA) and 22.20 muM 6-benzylaminopurine (BA). A hi gh percentage of tubercles explants of the M. elongata cristate form, excis ed from the tip of the branch and cultured on MS with 0.54 muM NAA and 0.44 muM BA or 1.07 muM NAA, responded by initially forming an inflated cristat e shoot, which gave cristate and normal shoots, without callus intervention , when transferred on basal MS. Callus formed on cristate tubercles explant s gave both cristate and normal shoots when transferred onto basal MS. Norm al and cristate shoots were rooted in vitro on MS with 9.84 muM or 0.98 muM indole-3-butyric acid, respectively, and established ex vitro. In both nor mal and cristate form, the differential response appeared to be associated with the site of the explant excision. The formation of shoots was influenc ed by the season of culture; i.e., explants excised in October had a higher shoot formation rate than those excised February.