Response of stem explants to screening and explant source as a basis for methodical advancing of regeneration protocols for chrysanthemum

Logical advancing of regeneration protocols as an end result of response to screening and use of alternate explants is reported. Stem explants screened on medium 1 (MS with 1 mg l(-1) BAP and 0.1 mg l(-1) IAA) produced 4 responses and were classified as Group 1: more than 1.6 shoots per explant; Group 2: less than 1.6 shoots per explant; Group 3: only callus and Group 4: no response. To regenerate groups 2, 3 and 4, specific media were developed (media 2 a,b, media 3 a,b and media 4 a-i). Media 2 and 4 had changes in hormonal combination compared to medium 1, while medium 3 had additional changes in vitamins. Nineteen out of the 37 cvs. tested were regenerated on stem explants, based on the response to screening technique. Cultivars recalcitrant on stem explants even after exposure to modified media were reinvestigated on leaf. High concentration hormone pulse as induction (medium 5) followed by a modified regeneration medium (medium 6d) ended in successful regeneration of leaf explants. Four out of the 14 cvs. recalcitrant on stem were successfully regenerated using leaf explants. Response-based advancing of regeneration protocols in addition to use of alternate explants for recalcitrant cultivars resulted in efficient regeneration of 23 of the 37 cvs. on assessment.