Studies on Vascular Infection of Fusarium oxysporum f. sp. cubense Race 4 in Banana by Field Survey and Green Fluorescent Protein Reporter

Fusarium wilt of banana (Musa spp.) caused by Fusarium oxysporum f. sp. cubense (Foc) is one of the most serious banana fungal diseases in the world. Understanding the infection process of Foc is important for development of effective ways in disease control. In order to follow infection and colonization of this pathogen from root to rhizome and pseudostem tissues of banana, a highly pathogenic strain FJAT-3076 of Foc race 4 (Foc4) was transformed with gene encoding green fluorescent protein (GFP) and the fungus carrying gfp (FJAT-3076-GFP) was used to inoculate banana plants (Cavendish cv. B.F.). After inoculation for 3 to 10 d, it was observed that the conidia and their germ-tubes had penetrated into epidermis of young roots. The hyphae were found inside the root xylem 10 d after inoculation in the rhizome and pseudostem xylem after inoculation for 17 d. All plants infected by Foc died in 24 d after inoculation. It was also observed that Foc had spread all over the xylem and part of hyphae reached the pseudostem surface. Hyphal population was found the highest in the pseudostem, lower in root and least in rhizome. Field survey confirmed that Foc4 were mostly present in the base of pseudostem and less in the rhizome. Thus, effective prevention of the Foc hyphae movement from the rhizome up to the pseudostem might delay or control banana wilt disease.