Cultivars of the genus Musa (bananas and plantains) have grown in East Asia and Polynesia for millions of years as herbaceous weeds, thriving as r-selected species in forest clearings1.
Circa 10,000 years ago, in modern-day Malaysia, natives discovered and succeeded in cultivating the hybrid of two different species: Musa acuminata (whose fruit is constituted of unpalatable flesh) and Musa balbisiana (where ½ of each ‘finger’ is flesh and ½ is seeds [Fig. 1]). The hybrid produced is sterile (having triploid chromosomes, whilst the original fertile varieties were diploid) and must thus be propagated by taking offshoots of their corms2. Crucial to the report, this results in the fruit being stenospermocarpic (i.e. with fruits containing aborted seeds), as seen in [Fig. 2]3.
This lack of sexual reproduction means that despite the fact there are over 1,200 cultivars of banana in the world, they are all, genetically speaking, remarkably similar.
This lack of genetic diversity has serious consequences in terms of disease resistance. From circa 1890 until the early 1960s, the variety of dessert banana cultivated for Western consumption was the Gros Michel. However, this variety of banana fell prey to Panama disease, and is now near extinct. Its replacement, the Cavendish (a Vietnamese variety which emerged about 60 years ago), is far more disease-hardy, but has an inferior taste and is much more prone to physical damage, especially in transit. However, a vast swathe of super diseases have now emerged, including Panama disease Race 44 and the deadly Black Sigatoka , that threaten even the Cavendish.
Panama disease is caused by the fungus Fusarium oxysporum; it causes irreparable damage to the roots ...
... middle of paper ...
Dan Koeppel, Popular Science Magazine, 19/6/2005
5. Phenotypic Diversity and Patterns of Variation in West and Central African Plantains (Musa spp., AAB Group Musaceae).
Rony Swennen, Dirk Vuylsteke, Rodomiro Ortiz.
Economic Botany, Vol. 49, No. 3 (Jul. - Sep., 1995).
6. IITA, 1992; Rony Swennen, 1990
Anne Dauwers, Nature, 28/06/07
8. Ploetz, R. C. (2000). "Panama Disease:A Classic and Destructive Disease of Banana". Plant Health Progress.
9. Meredith DS (1970) 'Banana leaf spot disease(Sigatoka) caused by Mycosphaerella musicola Leach.' (Commonwealth Mycological Institute, Kew, Surrey, England)
10. http://bananas.bioversityinternational.org/files/files/pdf/publications/tg4_en.pdf - 22 April 2010
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