Banana

No known vector.

There are several races of Fusarium oxysporum f. sp. cubense . The symptoms are similar for all races.

Tropical race 4, however, affects the "Cavendish" banana cultivar, which is resistant to other races of this disease. Surveys for tropical race 4 should only occur in "Cavendish" banana cultivars.

No specific signs are present.

Yellow and wilted leaves are typical symptoms of Panama disease of banana. The yellowing typically progresses from the older to the younger leaves. The yellow leaves may remain erect or collapse at the petiole and hang down along the pseudostem.

Banana suckers that are less than about four months old do not develop visible symptoms. The lack of visible symptoms on suckers has assisted in the movement of the pathogen to new regions through the movement of these asymptomatic suckers to new areas as planting material.

The fruit of the banana plant does not show any specific disease symptoms.

The first internal symptom, a reddish brown discoloration of the xylem, develops in feeder roots, the initial sites of infection. Vascular discoloration progresses to the rhizome, is most prominent where the stele joins the cortex, and ultimately proceeds up to and includes large portions of the pseudostem.

On plants that are more than four months old, the oldest leaves yellow or split longitudinally at the base. Eventually younger and younger leaves wilt and collapse until the entire canopy consists of dead or dying leaves.

Morphological for species-level identification.

The race of most pathogens is generally determined by inoculation of host differentials. Molecular methods are available in the literature to distinguish tropical race 4 (Dita et al., 2010; Dita et al., 2013; Peng et al., 2014) .

This fungus causes wilting symptoms in hosts but may be confused with other banana diseases. Symptoms similar to those caused by Fusarium wilt - such as leaf yellowing - may also be caused by other biotic and abiotic factors, including water stress. Care should be taken to avoid attributing such yellowing to Fusarium wilt by examining the plant for other external and internal symptoms, such as vascular discoloration In addition, there are several races of Fusarium oxysporum f. sp. cubense . Tropical race 4, however, affects the "Cavendish" banana cultivar.

Dita et al. (2010) have developed a rapid and reliable PCR diagnostic for Foc TR4 ⁄ VCG 01213 that can also be used for in planta detection. This is a major breakthrough in diagnostics for this pathogen. Dita et al. (2013) have since developed a nested PCR that is more sensitive and can detect TR4 in symptomless host plants and in soil. Peng et al. (2014) have developed a real-time fluorescence loop-mediated isothermal amplification (RealAmp) assay that is highly sensitive and can detect Fusarium oxysporum f. sp. cubense TR4 and distinguish it from subtropical race 4. This assay can be completed with the use of a portable fluorescent reader and no expensive reagents.