The fungus invades the vascular tissue (xylem) through the roots causing discolouration and wilting. The problem of this fungal disease is that the pest cannot be managed effectively with pesticides, fungicides or biocides. The only way to counter this threat is to create resistant cultivars via genetic modification.
Influenza virus and various strains of the fungus have evolved to attack different types of banana. These strains or subtypes that are pathogenic to bananas are classified into races based on the differential response of cultivars.
At this moment different four races are known, although some suggest that more races may exist. The problem is that these races are simply based on their differential response on cultivars and this means that there is no real scientific base for the current division. Novel Influenza subtypes are identified using accepted scientific analysis and that should also be the route forward with Fusarium oxysporum cubense.
|[Image: K. Nishimura]|
Race 2 preys on Bluggoe and closely related cooking cultivars.
Race 3 was reported to affect Heliconia species and to a lesser extent Gros Michel and seedlings of Musa balbisiana.
Race 4 strains attack Cavendish cultivars, as well as the cultivars that were also susceptible to Race 1 and Race 2.