The present invention encompasses compositions and methods to reduce orprevent microbial growth in plant tissue culture media, comprising adding achemical agent comprising methylchloroisothiazolinone, methylisothiazolinone,magnesium chloride and magnesium nitrate to a plant culture medium at aconcentration that reduces or prevents microbial contamination of the planttissue culture medium and that allows substantially normal germination ofseeds or substantially normal growth or development of plants, plant organs,plant tissues or plant cells. The chemical agent may further comprisepotassium sorbate or sodium benzoate, or both. The present invention furtherprovides a kit for germinating plant seeds or culturing plants, plant organs,plant tissues or plant cells on a plant tissue culture medium comprising thechemical agent.
