“The average fresh yield of cassava in Burundi is 9.9 tonnes/ha, which lags behind yields of 15–40 tonnes/ha achieved elsewhere,” said Ernest Vyizigiro, Head of the Institute of Agronomic Sciences (ISABU).
The IAEA, in partnership with the Food and Agriculture Organization of the United Nations (FAO), is supporting Burundian scientists in using nuclear technology to develop high-yielding varieties of cassava resistant to these diseases.
Some existing cassava varieties in Burundi are resistant to CMD, but not to CBSD, which first appeared in the country in 2011. “To date, all five cassava varieties resistant to CMB have succumbed to CBSD,”
Vyizigiro said. “This results in root rot nine months after infection.”
IAEA experts trained Burundian scientists in plant breeding techniques, using induced mutation and tissue culture techniques to develop a new cassava variety. Induced mutation speeds up natural changes in the genetic make-up of crops, so scientists can select mutant lines with desired traits such as disease resistance and eventually the best variety.
Since cassava plants take a relatively long time to grow, tissue culture techniques, where the cassava is grown in a controlled environment, are useful in multiplying the plants much faster than if they were planted on a traditional farming plot.
Cassava cuttings were irradiated at the Joint FAO/IAEA Plant Breeding and Genetics Laboratory in Seibersdorf, Austria before being sent back to the Gisozi research station in Burundi for further development and selection.
With support delivered through the IAEA technical cooperation programme, the tissue culture laboratory at the Gisozi research station was refurbished and endowed with modern equipment, which helps to provide the controlled environment needed to undertake advanced applied research in the field of crop improvement.
After a year of research and development, Burundian scientists have produced advanced cassava lines that are candidates for the development of cassava varieties resistant to both CMD and CBSD.
Thanks to training provided by the IAEA and FAO, these scientists are now able to study the mutant lines to see how well they perform in a new greenhouse at the research station. The greenhouse was financed by the IAEA.
“Using a greenhouse is important because you can’t take a plant directly from the tissue culture lab to the field – it will die. The best method is to expose the plant slowly to an outside environment in a greenhouse where certain environmental parameters are controlled,” said Bimpong. “Then it’s possible to evaluate the mutant lines to see which ones perform best.”
After further developing the mutant lines in the greenhouse, they will be taken to known hotspots in Burundi’s highlands, where both plant diseases are prevalent, to see which ones withstand the diseases.
Developing a disease-resistant cassava variety is particularly important for subsistence farming in Burundi, upon which 90% of the population depends.
“Subsistence farmers rely on cassava for vital nutrition, as it can be planted and harvested throughout the year, tolerates periods of unpredictable drought and grows on marginal soils,” said Dieudonné Nahimana, Director General of ISABU.
“Studies suggest that cassava may be highly resilient to future climate change and could provide Africa with adaptation opportunities which are not offered by other staple foods crops.”
For the best chance at the highest, healthiest yields possible, any new variety should be used in combination with soil fertility and water management methods, said Bimpong.
On research managed plots in Burundi, IAEA experts saw a significant increase in cassava yields using inorganic fertilizer and nuclear isotopic techniques to help manage water resources.
“Burundian scientists now have the proper equipment and training to further develop cassava varieties resistant to CMD and CBSD,” said Remmy Phiri, the IAEA Programme Management Officer responsible for Burundi.
“More research and development is needed before a variety can be released, multiplied on a large scale and distributed to the country’s cassava farmers.”