EFFECT OF SOME SELECTED FUNGICIDES ON THE GROWTH OF TISSUES CULTURED IN VITRO

Fungi were isolated from contaminated tissue cultures. They were initially characicriscdaccording to the colour and the texture of the colony and an identification number wasgiven to each. Pathogens were inoculated into seven different media in order to determinethe suitable medium for the rapid growth of the fungi and to obtain pure cultures. Theywere incubated at 27±1"C.Five different fungicides (diathanc. systhane, rovral, tumble blight and thiophenatemethyyl)were prepared at IOOppm concentration. Sterile filter paper circles (5mm) werewetted with 101 of each and were placed separately on the agar plates inoculated withfungal spores. They were in duplicates and were incubated for seven days. Using thediameter of the growth free area around the filter paper circles, the resistance or thesusceptibility of the fungi to each fungicide was determined.Most of the fungi were susceptible to dithane and thiophenate-methyl, thus these two werechosen for determination of the growth interference of fungicides on tissue cultures. Thesetwo fungicides were added to the tissue culture media after autoclaving the medium at ()(control), 20ppm and IOOOppmconcentrations. Twenty-five replicates per treatment wereused. After six weeks of incubation, the total numher of newly produced juvenile leaves,percentage or fungal contamination and the percentage number of surviving explants wereobserved. There was a significant difference between the two fungicides used and alsobetween the concentrations used. The interference of the fungicide to the growth of thetissue was minimal when thiophenate-methyl was added at IOppm concentration. Higherconcentrations retard the plant growth significantly.