Do you like to wear that same scarf everyday? Of course not, you have at least two or three. Variety is a natural inclination of nature. It should be allowed everywhere, otherwise there is trouble. Panama disease epidemic affecting banana cultivation is something similar and is a lesson to learn.
The recurring threat named Panama disease…
Domestication of banana started in prehistoric time about seven thousand years ago, as revealed by multidisciplinary research so far. The center of origin was the islands between south-east Asia and Australia. Breeding between two wild seeded Musa species, M. acuminata and M. balbisiana has produced a collection of edible variety, rich in genetic and visible phenotypic diversity. In this man handled evolution, the domesticated banana differed from their wild relatives significantly. They became seedless and incapable of sexual reproduction. However, only a few among them have always been chosen for mass cultivation. At present, the dessert banana, Cavendish variety is trending with 47 per cent of market share. In the late eighteenth century, however, a reportedly better tasting Gros Michel, a triploid (seedless) cultivar of M. acuminata was the dominant cultivar in the central and south America. In 1890 a wilting disease was noted in the Gros Michel plantations of Costa Rica and Panama. And it was severe as it eventually wiped out Gros Michel dominance by 1900. Can you believe? In 1910, the cause behind the devastation was disclosed. It is a fungus named Fusarium oxysporum f.sp. cubense as it was found in Cuba. This fungus dwells in the soils and colonize the plant root and can go up leaving the plant dry and sick. They are very hard to manage requiring hazardous soil treatment. The easiest and quickest way is to get a fungus resistant variety instead. Thus banana business regained balance by helping themselves with a replacement, the Cavendish bananas from Honduras and United kingdom. Cavendish, a subgroup of the triploid cultivar of M. acuminata was not susceptible to the race 1 fungal strain which savaged Gros Michel. But unfortunately, the message to take home from this mega event went unnoticed. Another round of risky monoculture with Cavendish bananas only initiated. The lesson was still to learn.
How could a pathogen be so powerful on earth?
Fusarium oxysporum is a cosmopolitan pathogen that affects a wide range of crops as separate host specific strains. They can wait in the soil as spores for the perfect condition for life. In addition the seamless evolution of resistant races makes them hard to overcome. Thus, Gros Michel still comprise 12% of banana cultivation, but only in soils free or unaffected by race 1 of Fusarium oxysporum strain. The problem with edible bananas is more severe as they are propagating asexually. Their is least chance of generating genetic variation possible in each round of sexual reproduction. They are more or less genetically identical clones of the first Cavendish banana planted. On the one hand it helps to preserve the fruit traits that in the first place were admired for leading to selection among other available varieties. However, the absence of genetic variation leaves them hopelessly vulnerable. This is a golden opportunity for any pathogen which are evolving anyway out there. A chance meeting with the susceptible clone is just what required. Rest of the population is ready for the doomsday.
Panama disease is now epidemic…
We are now a global society. Pathogens around the globe are also enjoying the benefits of this globality. They are spreading through all possible sources from infected plant material to sanitation loopholes. In 1960, Cavendish banana was attacked again in Taiwan. In 1994, the responsible strain Tropical race 4, the updated version of Fusarium was identified. Since the 1990s, this new Avatar has wiped out Cavendish plantations in Indonesia, Malaysia and is threatening business in Australia, Philipines, Jordan, Pakistan, Lebanon affecting approximately 100, 000 hectares of cultivation area in total.
Of course big banana farms are aware of this and vigilant. They have varieties in hand to start over with, if circumstance goes awry. But that doesn’t stop us from asking the simple question. No matter how much safety measures are followed – aren’t we allowing the fungus to gain the upper hand? If banana was allowed its fair share of experimentation – may be that would be savoury not only sweet!