Banana production is seriously threatened by Fusarium wilt, a disease caused by the soil-borne fungus Fusarium oxysporum f. sp. cubense. In the mid-twentieth century the fungi, also known as “Panama disease”, wiped out the banana industry in Central America. The devastation mitigated a shift toward resistant Cavendish cultivars, which are currently the main source of banana exports. However, a new strain attacks Cavendish clones and a range of other banana varieties. The spreading of this pathogen is of great concern due to the limited knowledge about the disease and the lack of management models, including resistant varieties and soil management approaches.
Biotechnology is predicted to be much more efficient at creating a resistant cultivar; however, we will discuss possible breeding strategies. The complicated hybrid genomes and the sterility of edible banana cultivars make it incredibly difficult to breed new cultivars with improved traits such as pathogen resistance or higher yield. Worldwide there are only twelve banana breeding programs that aspire to overcome the challenges of breeding. Due to bananas polyploid nature, breeders have to perform tetraploid breeding. Most edible bananas are triploid. To breed a new variety, banana breeders cross a triploid edible banana with a wild diploid seeded banana. The resulting tetraploid 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. Breeding bananas is tedious, time-consuming, labor-and space-intensive. Breeders must hand-pollinate them, then they search the pulp of an entire banana bunch for the occasional seed that may form. They then rescuing the embryo out of that seed to reconstitute a new, hopefully improved banana traits like higher yield or better resistance to pests and pathogens.
Through tetraploid breeding, we aim to breed a new cultivar with fusarium resistance. With this solution, I can not foresee any social backlash as most people are on board with breeding for certain traits. Economically, this new cultivar is likely to be more expensive for farmers which could cause some unrest but isn’t likely to have a huge impact. Politically, we would need to get into contact with communities all over the globe. All countries may not be on board with a new cultivar.
The path we aim to take is called 3x/2x breeding. The triploid parent will contribute anything from 1 to 3 chromosome sets because of its incapacity to undergo normal meiosis the hybrids resulting from a 3x/2x cross will either be diploid, triploid or tetraploid. We will only evaluate the tetraploid progeny to introduce to farmers because these hybrids are the only ones that have all the genes of the cultivar. Through this process we will breed until we obtain a cultivar with resistance to fusarium. This process is tedious and could take anywhere from 6 months to 10+ years. In our lab we would need a staff of plant breeders, growers, and testers. We would need at least 200 acres and a lab facility. We could hold trials and breed in one location if it is large enough. We would need to start off with many wild type seeds and our edible triploid seeds.
Banana production is seriously threatened by Fusarium wilt, a disease caused by the soil-borne fungus Fusarium oxysporum f. sp. cubense. In the mid-twentieth century the Fungi, also known as “Panama disease”, wiped out the banana industry in Central America. The devastation mitigated a shift toward resistant Cavendish cultivars, which are currently the main source of banana exports (Jain). However a new race of Foc, TR4, attacks Cavendish cultivars and a range of other banana varieties. The spreading of this pathogen is of great concern due to the limited knowledge about the disease and the lack of management models, including resistant varieties and soil management approaches.
Bio-engineering methods are predicted to be much more efficient at creating a resistant cultivar; however, this will later be discussed in future sections. The complicated hybrid genomes and the sterility of edible banana cultivars make it incredibly difficult to breed new cultivars with improved traits such as pathogen resistance or higher yield. Worldwide there are twelve banana breeding programs that aspire to overcome the challenges of breeding (fao.org). Due to most bananas polyploid nature, breeders have to rely om tetraploid breeding older cultivars. Some edible bananas are triploid. To breed a new variety, banana breeders cross a triploid edible banana with a wild diploid seeded banana. The resulting tetraploid 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. Breeding bananas is tedious, time-consuming, labor-and space-intensive. Breeders must hand-pollinate them, then they search the pulp of an entire banana bunch for the occasional seed that may form. They then rescue the embryo out of that seed to reconstitute a new, hopefully improved banana traits like higher yield or better resistance to pests and pathogens.
Through tetraploid breeding, we aim to breed a new cultivar with Fusarium resistance. Since there is no genetically modified part of this approach, there should be no social backlash. Economically, this new cultivar is likely to be more expensive for farmers which could cause some unrest but isn’t likely to have a huge impact. Unless genetic modifications are involved, politics would likely not play a large role in this new cultivar.
The path we aim to take is called 3x/2x breeding. The triploid parent will contribute anything from 1 to 3 chromosome sets because of its inability to undergo normal meiosis. The hybrids resulting from the 3x/2x cross will either be diploid, triploid or tetraploid. We will only evaluate the tetraploid progeny to introduce to farmers because these hybrids are the only ones that have all the genes of the cultivar. Through this process we will breed until we obtain a cultivar with resistance to fusarium. This process is tedious and could take anywhere from 6 months to 10+ years. In our lab we would need a staff of plant breeders, growers, and testers. We could hold trials and breed in one location if it is large enough.
One pitfall of this method is time. This method can take a substantial amount of time compared to other methods like gene editing. Another pitfall is reliability. There is no guarantee that by breeding 3x/2x will result in a disease resistant cultivar. Many years of funding and research can prove to be futile if no disease resistance is found.
http://modernagriculture.ca/plant-breeding-tools-crop-success/
https://www.frontiersin.org/articles/10.3389/fpls.2018.01468/full
Daniel and Bailey's Banana Biotechnology Blog 