In Vitro Mutation Induction and Selection of Chrysanthemum (Dendranthema Grandiflora Tzelev) Lines with Improved Resistance to Septoria Obesa Syd

This paper describes in vitro mutation selection technique for improved resistance in chrysanthemum (Dendranthema grandiflora Tzelev) cv. Snow Ball against culture filtrate of Septoria obesa, a leaf spot pathogen. The callus was initiated from leaf explant on MS medium supplemented with 10 mg/l kinetin and 1 mg/l NAA. Optimal doses of gamma radiation and culture filtrate on the per cent survival of calli were standardized. The optimal dose of gamma radiation was 20 Gy and that of culture filtrate was 15%. The selection of the resistant calli was made at 15% culture filtrate concentration and the calli were subjected to two more cycles of selection (30 day cycle) to obtain resistant cell lines. 100% of the plants raised from cuttings had acquired resistance against the pathogen in the pot in greenhouse. The plants were maintained for four years without any symptoms with regular inoculation of fungal spore suspension. No phenotypic variation was observed in the resistant plants.