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Fusarium is a species of fungus that affects the cultivation of a variety of crops. It is a plant pathogen that causes several diseases such as Fusarium wilt in bananas and solanaceous crops, head blight, crown rot and scab on cereals, etc.
Fusarium oxysporum, a Fusarium fungus species affects the cultivation of solanaceous crops such as potatoes, tomatoes, chillies, etc. Due to this, thousands of solanaceous cultivators had to face agricultural losses leading to low income and subsistence.
Fusarium oxysporum or Foc is a soil-borne fungus that affects the tissues of plants. It enters the plant’s vascular tissues through roots and deteriorates them. Vascular tissues help to transport minerals and nutrients within a plant. Any infection in these tissues can lead to plant death. Moreover, tackling this fungus is difficult as its spores remain in the soil even when infected plants and tissues are removed.
As far as commercial trade is concerned, the banana export industry is one such industry also affected by Foc. Some Foc strains are found to affect the Cavendish subgroup which is the most common species of banana exported worldwide.
The fungus has affected banana cultivation for several years. Researchers predict it will continue to affect banana production in Asian countries including China, Pakistan, Vietnam and the Philippines.
For Vietnam, the estimated loss of production could be 8 percent in the next five years. It may increase to mind-boggling 71 percent within the next 25 years. Particularly, the rise of the Fusarium TR4 strain is a matter of concern among Cavendish banana cultivators. However, a threat to banana production is not limited to TR4. The effects of some other Fusarium strains such as Race 1 and Race 2 are yet to be discovered. Race 1 and 2 strains of the pathogen are found to cause Fusarium wilt in Cavendish bananas.
Like most markets around the world, bananas are locally traded and consumed every day in Vietnam. Hence, banana production is the major source of earnings for Vietanemese cultivators. Any damage to the crop affects the income of local people.
Therefore, it is important to spot what fungal species cause Fusarium wilt in bananas. Knowing what specific species are associated with infections in bananas can help to control spread in other regions.
A team of researchers from Vietnam, the Netherlands and Belgium investigated the identity of Fusarium wilt in bananas. They used DNA analysis and morphological characterization of the banana plant to determine the cause. Morphological characterization is the procedure to study the morphology of the disease-causing strain that includes shape, size, homogeneity (strains similar characteristics), opacity (strain visibility) and texture of the strain colonies. It helps in microscopic observations to determine cell shape, size and mobility.
The study showed that 3 out of 4 infections in bananas were caused by a Race 1 strain, F. tardichlamydosporum. Interestingly, the Foc TR4 strain was not the dominant cause of the disease in northern Vietnamese bananas. Researchers found some new strains other than TR4 causing the disease, such as F. odoratissimum, causing 10 per cent of the infections. A similar proportion of Fusarium infections were caused by the species Fusarium cugenangense. This species is known to cause Race 2 infections in bananas.
Researchers found that Fusarium wilt not only infected cultivated bananas but also affected wild bananas. This finding indicated that wild bananas might act as reservoirs of Fusarium wilt. From these bananas, reinfections could take place in cultivated ones.
The detailed study results have been published in the journal Mycokeys.
Contributed by: Simran Dolwani
