Source: The Federal [edited]
Grand Nain banana, a variety under Cavendish cultivar, is being affected with a mutated strain of TR1 fungus _Fusarium oxysporum_. "Grand Nain is known to be resistant to TR1 and TR2 and susceptible to TR4. But these bananas are also prone to a newly found mutated strain of TR1," said Dr R Thangavelu, National Research Centre for Banana (NRCB).
In 2009, Thangavelu 1st showed the TR1 can also affect the Cavendish cultivar [ProMED-mail post 20... & link below]. It was detected [on Grand Nain] in Theni district [State of Tamil Nadu] and many banana growers shifted varieties. Now, TR1 is affecting Cavendish cultivars in states like Gujarat, Maharashtra, Madhya Pradesh and West Bengal, said Thangavelu, adding that more problems are in the offing.
"A mutated strain of TR1 has been recently identified in Bihar and Uttar Pradesh. It means, though for academic purpose we name the fungus types differently, the fungus which affects the Grand Nain variety is everywhere," said Thangavelu, whose paper on this new strain was published [link below].
[Byline: N Vinoth Kumar]
[Panama disease of banana (PD, also called fungal or fusarium wilt) is caused by the soilborne fungus _Fusarium oxysporum_ (previously f. sp. _cubense_). Symptoms include yellowing, wilting and streaking of pseudostems; affected plants die rapidly. The pathogen is spread by infected planting material, mechanical means (including human and insect activities), soil and water.
Disease management for PD is difficult and mostly relies on phytosanitation for pathogen exclusion. The fungus can survive in the soil for decades; consequently, crop rotation with non-hosts is not likely to control the disease effectively. No effective chemical or cultural control measures are available. Integrated approaches have been developed (ProMED-mail post 20090419.1483), which may include cultural practices, certified clean planting material and biocontrol agents such as _Trichoderma_ species (for example, ProMED-mail post 20160317.4102576 and see link below). Breeding programmes and molecular techniques are being used to develop crop cultivars with increased resistance or tolerance to the different fungal strains. Constant vigilance is required in areas where the fungus is present to prevent flare-ups and recognise emerging new strains.
Several races of the pathogen exist, varying in host range. Cavendish banana varieties (_Musa_ AAA, see links below) replaced the original eating varieties (such as Gros Michel) because they are resistant to the original fungal strain. They include most of the current commercial eating bananas. Cavendish-affecting strains have emerged since from Asia and Oceania, for example from temperate (subtropical) and tropical races 4 (TR4), as well as the new strain of race 1 in India referred to above (ProMED-mail post 20101223.4510). TR4 in particular is of great concern worldwide.
It is unclear from the story above or from the source paper (link below) whether further variations of the earlier Cavendish-affecting TR1 strain are thought to have occurred during its spread to the different states.
India (with states):
PD symptoms on banana:
_F. o._ f. sp. _cubense_ culture:
Information on Panama disease:
Cavendish-affecting TR1 in India:
_F. oxysporum_ taxonomy and synonyms:
Information on _Trichoderma_ species and use as biocontrol agents:
Cultivars and hybrids of banana and plantain: