Huge progress in breeding anthracnose-resistant sorghum
Dr Girma Mengistu Digafe
Sorghum is one of the three most important cereal crops in Ethiopia, but it has a lethal enemy that flourishes in the wet, warm west of the country.
This disease, sorghum anthracnose, is caused by Colletotrichum sublineolum Henn, a fungal pathogen that attacks most parts of the plant and can cause yield losses of up to 67% in Western Ethiopia.
“Anthracnose attacks sorghum badly and is the most serious disease in that area, because the high levels of rainfall, humidity and temperature create good conditions for this disease,” says ACCI PhD graduate, Dr Girma Mengistu Digafe.
He focused his doctoral research on breeding anthracnose-resistant sorghum, which is seen as a more sustainable and environmentally-friendly solution to controlling this disease than other methods such as crop protection chemicals and cultural practices. The study was financially supported by the National Research Foundation of South Africa, and the Agricultural Growth Programme of the Oromia Agricultural Research Institute in Ethiopia.
Digafe grew up on a small farm in Ethiopia where his parents, who were part-time farmers, grew maize, tef and sorghum. His background lead him to study plant science and then a master’s degree in plant breeding, and he came to Pietermaritzburg to join the ACCI PhD programme in 2016, under the supervision of Professor Hussein Shimelis.
Digafe, who is currently based at Oromia Agricultural Research Institute in Addis, conducted his doctoral study at Bako Agricultural Research Centre, in an area where most of the farms are small. He started by speaking to about 165 farmers to get their views on the main challenges facing sorghum in the area, and what their preferred traits in improved varieties would be.
The farmers identified anthracnose, birds and a disease called Smut as significant challenges, while yield and cooking quality were their desired traits
Breeding for anthracnose resistance requires identifying genomes that contain the genes for this trait. To do this, Digafe collected more than 300 different landraces from the Ethiopian Biodiversity Institute for a diversity study. These landraces were planted and screened to determine genetic variability, based on agro-morphological traits and anthracnose resistance, and thereby select breeding parents.
Seeds from a diverse collection of Ethiopian landraces were inoculated with the fungus and planted. After two years 32 promising materials that were resistant to the disease were identified and the best candidates were selected for further breeding.
Digafe assessed the genetic diversity of the selected plants using molecular seed markers called single nucleotide polymorphism (SNP) markers. This provided the basis for choosing superior parents and families for further breeding.
“I was looking at how similar the genotypes are,” he says. “You need diversity to get hybrid vigour, so I was looking for parent plants that are different enough from each other.”
He selected nine parents that were crossed and planted in two locations, to determine if there was heterosis or trait enhancement. Some of the crosses showed less disease reaction than the parents.
“I will carry on working on this in Ethiopia. With these materials I have a good basis on which to produce sorghum that’s resistant to anthracnose,” says Digafe.