IN VITRO MUTAGENESIS STUDIES IN GLADIOLUS FOR INDUCTION OF RESISTANCE TO FUSARIUM OXYSPORUM F.SP. GLADIOLI

Gladiolus is one of the important geophytes in India, being grown on 1000 hectare. It is highly heterozygous and, as it is propagated through corms which makes it suitable for mutagenesis. Fusarium yellows of gladiolus caused by Fusarium oxysporum f.sp. gladioli (FOG) is an international problem and causes 60-100% losses in various parts of the world. Shoot clumps of gladiolus 'Eurovision' and 'Wine & Roses' multiplied in vitro were irradiated with different doses of ⁶⁰Co gamma rays. Survival of irradiated shoots decreased with increased dose of ⁶⁰Co gamma irradiation. A dose of 50 Gy had the lowest survival rate but was sub-lethal. Plants of 'Wine & Roses' and ‘Eurovision’ surviving this dose of gamma irradiation were multiplied on GMM-7 (MS medium + 2 μM KIN) and GMM-8 (MS medium + 4 μM KIN), respectively. In vitro selection by challenging with fusaric acid (1-1.5 mM) and culture filtrate (20 %) of F. oxysporum f.sp. gladioli resulted Fusarium yellows insensitive mutants at the end of the 3^rd selection cycle. Ex vitro evaluation further confirmed that fusaric acid and culture filtrate were suitable phytotoxins for selecting optimal resistance against FOG.

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