Lewis
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Bananas have been an important food for humans for at least 7,000 years, but the most popular types are sterile varieties that make farming easy but hold little genetic diversity - a recipe for disaster in the face of plant disease, a paper by scientists from Australia and Europe finds.The researchers, writing in this week's edition of the journal Proceedings of the National Academy of Sciences, traced early banana cultivation to the Kuk swamp of New Guinea around 5,000 BC. The plants spread throughout southeast Asia and into Africa, almost certainly via human intervention.
Bananas are a crucial source of food for tropical and sub-tropical nations, especially Africa, ranking after rice, wheat and corn in importance. More than 85% of bananas are grown for local consumption. Most are not the sweet dessert varieties eaten in the west, but starchy plantain-style bananas that must first be cooked.
The banana probably arose in the islands around Southeast Asia and western Melanesia. It was hybridized into subspecies that could not have been created without human intervention - the only way to grow more of these bananas is to take a shoot from a banana plant, as the seeds are generally not viable.
This means that most banana plants are clones, with no genetic variety. A good example is today's Cavendish, the main banana sold in the United States and Europe. All come from clones of the same tree and all are genetically identical.
The problem with having so many people rely on a few strains of an important food crop is that they are very venerable to disease. For example, up until the 1950s most bananas eaten in the United States were the Gros Michel type, which was wiped out by a fungal disease known as Panama disease.
As the researchers say in their paper:
Researchers: Bananas too inbred to fight disease - Science Fair: Science and Space News - USATODAY.com
Bananas are a crucial source of food for tropical and sub-tropical nations, especially Africa, ranking after rice, wheat and corn in importance. More than 85% of bananas are grown for local consumption. Most are not the sweet dessert varieties eaten in the west, but starchy plantain-style bananas that must first be cooked.
The banana probably arose in the islands around Southeast Asia and western Melanesia. It was hybridized into subspecies that could not have been created without human intervention - the only way to grow more of these bananas is to take a shoot from a banana plant, as the seeds are generally not viable.
This means that most banana plants are clones, with no genetic variety. A good example is today's Cavendish, the main banana sold in the United States and Europe. All come from clones of the same tree and all are genetically identical.
The problem with having so many people rely on a few strains of an important food crop is that they are very venerable to disease. For example, up until the 1950s most bananas eaten in the United States were the Gros Michel type, which was wiped out by a fungal disease known as Panama disease.
As the researchers say in their paper:
Current global production of more than 100 million tons is based on large-scale vegetative propagation of a small number of genotypes, which derive from only a few ancient sexual recombination events. These genetically restricted and inflexible clones are particularly susceptible to diseases, pests, and current ecological changes.
Plant breeders need to understand the "sequence of crossings and selections that occurred minimally during the past 6,500 years" so that they can find other crosses that can withstand disease and pest outbreaks that might hit this important plant, they say.
Researchers: Bananas too inbred to fight disease - Science Fair: Science and Space News - USATODAY.com