Cowpeas are an important food crop in Sub-Saharan Africa but yields are often reduced by more than 80 per cent due to pests and diseases. We are part of a global project to improve cowpea production in Africa and are making progress towards incorporating ‘built-in’ insect pest protection that could help to reduce food shortages in the region.
Increasing food security for Sub-Saharan African farmers
Cowpeas are a staple food and an important source of protein for more than 200 million people in Sub-Saharan Africa. They are mostly grown in West Africa on an area of more than seven million hectares.
Cowpeas have been used in this part of the world for millennia. They are regarded as drought tolerant and can cope with poor soils, making them highly adapted to the region.
One additional advantage of cowpeas is that the leaves and green pods can be eaten before crop maturity. This provides an important food source before mature grain is harvested – acting as a food bridge during the 'hunger gap' between harvests.
Protecting African cowpeas from insect pests
We are combating one of the major pests that affect cowpeas – the legume pod borer.
Legume pod borers deposit eggs on the flower buds of cowpea. When the larvae emerge they damage the flowers, young pods and seeds, drastically reducing yield.
Using insecticides has not proven to be a viable approach. They are expensive and their safe handling and use requires equipment and expertise that is not readily available to small-scale farmers in sub-Saharan Africa.
One option to address these pests is to develop cowpea varieties with their own 'built-in' protection against the pod borer.
Researchers in Africa have been looking for pest resistance in extensive collections of cowpeas and related species, but useful levels of protection have not been found.
As a result CSIRO was approached by the African Agricultural Technology Foundation (AATF) to develop a system for genetically engineering cowpeas, which is a basic requirement to introduce new genes for insect protection.
Similar to cotton, where Bt genes are providing resistance to cotton's number one pest – Helicoverpa, we are using a Bt gene in cowpeas to protect against pod-borers.
The Bt gene causes the plant to produce a protein that selectively affects certain insect pests including the pod borer without affecting others, including beneficial insects.
Successful glasshouse and field trials of resistant cowpeas
Significant progress has been made toward the ultimate aim of incorporating one or more Bt genes into cowpeas to provide a long term plan for robust protection.
The team has been able to develop several pod borer resistant cowpea lines, each producing different amounts of the Bt protein.
Trials were first carried out in greenhouses at our Black Mountain site in Canberra.
In the lab the research team found that there was 100 per cent mortality of the pod borer caterpillars after feeding on flower buds of cowpea containing the Bt gene.
Field trials to test agronomic performance and insect resistance have been carried out over several years in Puerto Rico, Nigeria, Burkina Faso and Ghana and recently in Malawi in Southern Africa.
Field results were very promising. Selected cowpea lines were fully protected in Nigeria, Ghana and Burkina Faso over several years. The cowpea plant breeders have introgressed the Bt gene into farmer-preferred varieties and evaluated their acceptability and suitability for local environments.
Transferring the benefits to Africa
In late 2019 the final stage of regulatory approvals came through with the successful registration in Nigeria of the new insect-resistant cowpea variety SAMPEA 20-T, paving the way for commercial cultivation.
Besides developing improved breeding material, CSIRO also aims to transfer knowledge of the technology to Africa.
Several African stakeholders including regulators have visited the Canberra-based group already and have benefited from their experience by establishing protocols based on what they learned in Australia.
This research is managed by the African Agricultural Technology Foundation with financial support from USAID and the Rockefeller Foundation.