Infection and colonization of common bean by EGFP transformants of Fusarium oxysporum f. sp. phaseoli

Fusarium wilt, caused by the fungus Fusarium oxysporum f. sp. phaseoli (Fop), is regarded as one of the most severe diseases of common bean prevalent in crop fields across the world. However, the development and progression of this disease is poorly understood. Fop Brazilian race 2 was transformed for egfp gene expression and the resulting fungal transformants were used to study the infection and colonization process in the root and stem tissues of common bean. A combination of Driselase and Lysing Enzyme was found to be efficient for protoplastization of Fop mycelium. The PEG-CaCl2 based transformation protocol could obtain stable transformant fungi with colonies expressing the egfp gene. Regarding colonization by Fop transformants, the fungus was observed to grow in root hair epidermis intercellularly, post-inoculation (DPI) at 6 days and on parenchymal cells at 11 DPI. The fungus reached the xylem vessels at 19 DPI, blocking water and mineral passage to the shoots resulting in plant death at 25 DPI. This study adds to the existing information of Fop dynamics during the colonization of common bean tissues.