Introduction
Panama disease, also called fusarium fungal wilt, is a soil-borne illness that endangers the development and productivity of a wide range of agricultural crops across the globe. Panama disease, often referred to as banana wilt (FWB), is brought on by an infection with Fusarium oxysporum f. sp. cubense (Foc). There are four pathogenic races of the disease: tropical race 4 (TR4), which affects Cavendish bananas and plantains, race 3 which causes pathogenicity in Heliconia spp., race 2 which causes disease in ABB frying bananas, and race 1 which causes outbreaks in ‘Gros Michel’ AAA. In many banana-growing regions, TR4 has emerged as the most devastating disease in recent times. For more than 400 million people, bananas—the fruit with the highest global production rate—are a staple diet. However, because FWB is so easily transmitted, it poses a severe danger to the global banana sector. As a result, FWB has drawn the interest and concern of researchers.
Colonization of Fusarium oxysporum f. sp. cubense in banana tissue
FWB, a vascular wilt disease, is a hemibiotrophic pathogen that creates a biotrophic relationship with the host, causing the death of the host tissues. It can cause multiple cycles of infection, with larger roots less affected and sometimes infected through the rhizome. Chlamydospores in the soil germinate in the presence of nutrients, banana and non-host plant exudates, or in contact with non-host plant residues. These spores are resistant to desiccation and extreme environmental conditions and can survive for over 30 years in the soil.
The initial transfer from roots is slow, but in mature xylem vessels, the pathogen travels with each new generation every 30 cm for three days. Once reached the rhizome tissue, the pathogen can infect the entire pseudostem in less than 2 weeks. Extensive formation of conidia within the xylem tissues facilitates colonization.
New findings on FWB colonization show that when fungus infects the root, it directly penetrates the epidermal cells of the root tip and grows intercellular in line with the elongation zone. The colonization process occurs without limitation in Gros Michel and Cavendish cultivars, but gel accumulation and vascular parenchyma impede further colonization. Foc 4 can penetrate into banana roots from both intercellular spaces of the epidermis and wounds, while Foc1 mainly penetrates from wounds.
FWB colonization results in senescent leaf sheaths, and cultural practices such as de-leafing may increase the risk of returning chlamydospores to the soil and enhance the risk of colonization.
Control of fusarium wilt disease
By keeping Fusarium wilt (TR4) out of the banana plant and slowing its spread, yield loss can be minimized. Scientists demonstrate that funding for exclusion and containment strategies yields highly beneficial outcomes and allocating resources to slow down the spread of TR4 are a wise investment. A high internal rate of return on investment is produced by several scenarios, including enhanced exclusion,, breeding resistant cultivars, integrated crop and disease management, and creating genetically modified resistant banana cultivars, all of which considerably minimize future output losses.
Early pathogen identification using trustworthy diagnostics is essential for the successful execution of containment and quarantine protocols. Using Secreted (effector proteins) in Xylem (SIX) genes, researchers devised a molecular diagnostic assay that is capable of accurately identifying Race 1, Subtropical (SR4), or TR4 strains in addition to FWB strains and species. This work demonstrates that the pathogen’s genetic analysis may identify specific strains, providing insight into the genesis and spread of TR4.
More cropping system research is required to make novel resistant clones more durable. In certain areas, it is still possible to grow Race 1 vulnerable types like “Prata” and “Gros Michel” profitably if they are grown in conjunction with strict cultural approaches. To control FWB, soil management involving biotic and abiotic components is necessary. However, utilizing realistic biological, pharmacological, or cultural means, control of FWB has not been satisfactorily attained in large-scale monoculture systems based on Gros Michel or Cavendish.
