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Researchers achieve breakthrough in reinforcing plantain against devastating microscopic worms
05 April 2012
International Institute of Tropical Agriculture (IITA)
For the first time ever, scientists have built into plantain a viable genetic defense against nematodes – microscopic worms that infest and eat away at the plant’s roots, making them easily topple over and significantly reduce their production. Apart from bacterial wilt diseases, nematodes are among the most economically devastating pests of banana and plantain, the fourth most important staple in sub-Saharan Africa.
In experiments, researchers infused maize cystatin gene and a synthetic nematode-repelling protein into the plantain, cv. Gonja manjaya. The cystatin introduced from maize kernel prevents nematodes from digesting proteins, literally “starving” them to death and greatly reducing their population. On the other hand, the nematode-repelling protein makes the plantain’s roots secrete a synthetic peptide that disables the nematodes’ ability to find the host. In the study, scientists infused the plantain with either one or both of the genes for single or dual nematode defense.
Feeding on the roots, nematodes restrict the flow of nutrients into the plants thereby stunting their growth. Farmers easily lose 40% or more of their produce because of nematode infestation, especially in areas frequented by tropical storms and high winds. This is because nematodes damage the roots, weakening the plant’s anchorage and causing them to completely topple over in strong winds. Plants heavily laden with harvest-ready bunches are especially susceptible.
The transformation research was conducted by a team from the International Institute of Tropical Agriculture (IITA) and the University of Leeds. The results of the study have been published in the latest edition of the journal Molecular Plant Pathology.
The study assessed 245 independent transgenic lines (plantlets) for resistance to nematodes in screen house trials. Researchers have identified the 11 strongest lines that will be further evaluated in confined field trials in Uganda after getting approval from the country’s National Biosafety Authority.
“This is indeed a breakthrough in the fight against one of the most damaging pests of plantain, which many farmers are usually not aware of because they are too small to be seen by the naked eye,” says Dr Leena Tripathi, IITA's biotechnologist and one of the researchers in the study.
“This research has given us highly promising resistant lines as part of our efforts to enhance food security for the millions of people who depend on the crop for their food and income,” she added. “And while the safety of the two genetic interventions has been proven in many other similar researches, we will still carry out further safety studies during the field trials to ensure that they pose absolutely no risks to humans or the environment,” she emphasized.
The cystatin, which naturally occurs in maize kernel, has been in the diets of humans for as long as maize has been consumed. The safety of cystatin-based transgenic work has also been well-established in rice for years. Additionally, scientists say a similar protein is present in human saliva.
Safety studies of the synthetic peptide, on the other hand, show that it is destroyed by the high temperatures required for cooking plantain and by digestive fluids in the intestine. In addition, the protein is listed as not being a potential allergen in the Allergenonline and Allmatch, reference tools recognized and used by WHO and FAO.
Pest management in banana is mainly based on crop rotation and chemical control. However, crop rotation is not often practiced due to unavailability of land while most subsistence farmers cannot afford nematicides. Although conventional breeding against the pest is an option, sources of nematode resistance and tolerance among existing banana and plantain varieties are very limited. Banana and plantain are also mostly sterile and do not produce seeds, thereby making conventional breeding difficult, slow, and long drawn. However, these same qualities make them safe for biotechnology-based transformation as there is minimal risk of contaminating local varieties.