**4. Disease cycle and epidemiology**

Beckman and his colleagues considered the internal responses for susceptible banana cultivars to infection by *F. oxysporum* f. sp. *cubense*. They observed that race 1 strain of the pathogen produced rich microconidia in xylem vessels of cultivar Gros Michel. These propagules move acropetally in vessels by means of the plant transpirational change which caught at the scalariform parts of the bargains. As the fungus develops, it colonizes inside vessel end within 2–3 days, delivered microconidia on its adaxial side, along these lines empowering the pathogen to travel through another vessel (**Figure 3**). This procedure proceeded with unabated in Gros Michel, yet stopped in a race1 safe Cavendish cultivar not long after was it immunized. In the later case, gels formed in infected vessels in 24–48 h, followed by the development of vascular parenchyma into vessels after 48–96 h. These pathogen-incited exercises in the host caught spores of the pathogen and precluded it further colonization from claiming the host. At last, the host discharged phenolic aggravates that infused and lignified the blocking structures. Consequently, in a safe cultivar, there is a reasonable and quick coordination of host defences to ensure the systemic colonization of the xylem does not happen.

Rhizomes (suckers) are utilized generally as vegetative seed pieces for banana cultivation. Since they are generally free of symptoms when they are early infected by *F. oxysporum* f. sp. *cubense*, are a typical methods by which this pathogen is spread. The pathogen spreads in soil, running water, farm executes and apparatus. Work in the early trade estates showed that susceptible clones could not be successfully replanted in an infested site for as long as 30 years due to the long term survival of *F. oxysporum* f. sp. *cubense* in soil and as a parasite of nonhost weed species. Root tips are the characteristic, starting locales of infection; injured rhizome surfaces are evidently minor infection courts. Much of the time, root-tip infections are halted soon after the pathogen arrives at the xylem, and responsible for the formation of gels, tyloses and vascular breakdown. Macroconidia and chlamydospores

**Figure 3.** *Disease cycle of* Fusarium oxysporium *f. sp.* cubense*.*

*Fusarium Wilt: A Destructive Disease of Banana and Their Sustainable Management DOI: http://dx.doi.org/10.5772/intechopen.101496*

are formed on dead or passing on plants. The last propagules are the most significant survival structures of pathogen.

Weather factors like prolonged wet or dry conditions, extremes in temperatures, storm damage and soil conditions like poor soil drainage, aeration, unfavourable chemical or physical conditions also play a major role in influence on the wilt disease [4]. An internal water deficit due to dry conditions or waterlogging promotes expression of symptoms [5]. Temperature is a critical factor in panama wilt development [6]. Peng et al. [7] reported that the growth of Fusarium wilt pathogen is usually maximum at 28°C, and reduced above 33°C and below 17°C.
