ISOLATION AND CHARACTERIZATION OF WILD STRAINS OF AGROBACTERIUM FROM CROWN GALL INFECTED PLANTS

Abstract

Agrobacterium tumefaciens is a plant pathogen that has immense importance in plant genetic engineering. Its pathogenic strains have a large tumor inducing plasmid that can transfer and integrate transfer DNA segment in the plant genome and help in generation of transgenics. The highly virulent bacteria can transform plant cells more efficiently as compared to non-virulent strains. Keeping in view this fact twenty-five wild strains of Agrobacterium were isolated from infected plants of Mango, Sita ashok, Chikoo, Neem, Eucalyptus and Gulmohar growing in the Horticulture Garden, of Sindh Agriculture University, Tandojam. Fifteen isolates out of twenty-five were designated as A. tumefaciens on the basis of morphological, biochemical and phyto-pathological testing. Among these fifteen isolates, three were found nonpathogenic strains of A. tumefaciens whereas remaining twelve revealed tumor forming ability on carrot discs in an in vitro disease assay. Isolate AtMi003 of twelve A. tumefaciens was found the most virulent strain on the basis of tumor quantity generated and analyzed through ANOVA and LSD at p= 0.05. It showed 80% transformation efficiency and 23.67 mg tumor weight on carrot discs.