Have you ever tried eating a wild banana? No?! Good! I can tell you, it would not be a pleasant experience. Wild bananas are small. With little fruit pulp. And they are full of large seeds that are hard as stones.
Luckily, thousands of years ago, farmers in South-East-Asia discovered natural mutants of banana. These mutants were hybrids resulting from a cross of two wild banana species. They were sterile. And therefore seedless! And therefore: Edible!
Since this time, farmers have propagated the seedless bananas vegetatively by replanting the suckers – the young banana plants emerging next to the mother plants. Essentially, bananas are all clones of one another.
The problem with clones is that they are highly vulnerable to pests and diseases. In East Africa, where banana consumption is higher than anywhere else in the world, 90% of the banana yield is lost to pests and diseases. When you think about bananas, you probably think of the Cavendish. The Cavendish is THE banana that you find in supermarkets worldwide and its production is severely threatened by a new aggressive strain of Fusarium wilt – called TR4 – that is spreading around the globe.
Banana breeding – a tedious task
Because the banana is seedless and sterile, breeding bananas is incredibly challenging. Worldwide there are only 12 banana breeding programs that dare to tackle this challenging task. They have to take a complicated route called tetraploid breeding. Edible bananas are triploid. That means these bananas have three copies of their genome. To obtain a new banana variety, banana breeders first cross a triploid edible banana with a wild diploid (two genome copies), seeded banana. The resulting tetraploid (four genome copies) is then again crossed with a diploid to result in an improved triploid banana. Because the triploids are often sterile, seed production is generally low – sometimes a complete bunch (60-70 bananas) have to be smashed to recover a single banana seed! Breeding bananas is tedious, time-consuming, labor-and space-intensive.
Biotechnology – the Way to Go
In Nairobi, Dr. Leena Tripathi pioneered a new approach. She is using biotechnology to improve disease resistance in bananas. She and her husband – Jai Tripathi – have established a system to transform banana plants with resistance genes. The results are banana plants that are identical to their parent in terms of yield and taste. In addition, they are also resistant to certain plant diseases.
Dr. Tripathi works at the International Institute for Tropical Agriculture (IITA). IITA is one 15 research centres of the Consultative Group for International Agricultural Research ( CGIAR ). The mission of the CGIAR group is to combat the world’s most pressing challenges: poverty, hunger, food security and environmental degradation by delivering research from field data to integrated solutions. Ever since peace Nobel prize winner Norman Borlaug started the green revolution with his high-yielding, rust-resistant wheat cultivars, much of the impact of the CGIAR centres has come from genetic improvement of crop plants.
By transforming bananas, Dr. Tripathi has already obtained banana plants that are resistant to Xanthomonas wilt – a bacterial disease that is killing banana plants in East Africa. Her Xanthomonas-resistant bananas are currently in the third phase of field-testing and will probably be released to farmers in 2019. Since CGIAR and IITA are committed to improving the lives of subsistence farmers, the resistant bananas will be given to farmers without any charge and the freedom to propagate them as they wish.