Fast forward 50 years, and there is a new strain of Panama disease that threatens the worlds’ supply of Cavendish bananas and has been spreading around the globe since 1992. It is important to realize that Panama disease Race 4 is so virulent that if someone stepped on the fungus in Australia, took a plane to Costa Rica and stumbled across a banana field, all of Costa Rica could be infected within a few years). Already, it has wiped out entire plantations in Indonesia, Austrailia, Malaysa, Taiwan and is currently spreading through Southeast Asia (Prisco 2016).
In fact, Malaysian plantations were completely desolated by the fungus in less than five years. It is only a matter of time before it surfaces in Africa or Latin America. Unlike in the US where the banana is one of hundreds of fruits we have access to, the banana is a dietary staple in many of the countries in which it is grown (De Langhe et al. 2009). Meaning that when the banana, a major source of nutrition for its native people, dies the people die too. Bananas have contributed over several thousand years to the diets of numerous people in the tropics and subtropics. Current global production of more than 100 million tons is made capable by large-scale vegetative propagation of a small number of genotypes, derived from only a few ancient sexual recombination events. These genetically restricted and inflexible clones are particularly susceptible to diseases. The challenge for banana improvement is to produce a resistant and sterile polyploid hybrid through genetic recombination of fertile diploids that meet consumer expectations for each Cavendish type (Perrier et al. 2011).
The required breeding strategy will need to reproduce the sequence of crossing and selections that occurred minimally during the last 6,500 years, while intentionally substituting some genetic code from related species for their level of resistance to biotic and abiotic stressors. Development of new super-banana hybrids have been particularly difficult due to the complex nature of banana reproduction. Bananas are unique in that species can be diploid, triploid, or tetraploid (Hirst 2018).
Bananas currently on the market are sterile and parthenocarpic, which is why bananas are clones of each other and result in fundamentally low species diversity and monocultures. But the difficulty of banana genetics and sterility of the crop has made development of new bananas through hybridization and genetic modification relatively slow and unsuccessful.
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