Vangi Ekirapa, a farmer in Tororo, has for long been struggling to increase yields in her cassava garden.
By Christopher Bendana
Vangi Ekirapa, a farmer in Tororo, has for long been struggling to increase yields in her cassava garden. But with the introduction of NASE 14, a hybrid cassava variety, Ekirapa has a reason to smile because she is able to harvest about 12kg of cassava from each stem. NASE 14 was developed at the National Crop Resources Research Institute (NaCRRT), Namulonge.
Cassava production in Uganda is largely affected by Cassava Mosaic and the Cassava Brown Streak Disease (CBSD). Cassava mosaic affects mainly the leaves, which turn yellow consequently affecting the photosynthesis of the plant. This leads to poor yields. CBSD affects the roots turning them brown.
Experts breed varieties
Currently, geneticists and plant breeders are breeding new cassava varieties. The new variety is a cross between a breeder’s two desired varieties each with traits a breeder is looking for. The traits include drought and water resistance, pests and diseases resistance and high yielding traits.
For pollination to take place the female part of the cassava is covered to stop fertilization by its male counterpart of the same variety. The female is monitored before it opens up for pollination. The breeder then introduces a desired male cassava variety, which he pollinates manually in a process called controlled pollination.
Controlled pollination has been going on for many years at the National Crop Resources Research Institute (NaCRRT), Namulonge. So far, 19 new varieties from NASE have been breed.
Why is breeding vital?
According to William Esuma, a research assistant at NaCRRT, cassava breeding is aimed at solving the problem of low yields, pests and diseases by introducing improved varieties, especially those from the International Centre for Tropical Agriculture (IITA).
“We aim at increasing cassava yields, varieties that are resistant to pests and diseases and are high in nutrient composition, especially proteins and vitamin A,” Esuma explains.
According to the World Health Organisation, lack of vitamin A, especially in children is the major cause of blindness across the globe.
“We also want to get cassava varieties that mature early and have a long life span. This will increase market opportunities for farmers,” he adds.
How it is done
The breeding process involves selection of a desired cassava variety that has one or more of the desired traits like resistance to drought, pests and diseases and high yields. It is then pollinated with another that has other desired traits.
Anthony Pariyo, a breeder at NaCRRT, says the local landraces, which they have been improving include Kakwele and Bamunanika.
They are crossed with varieties like TME14 from IITA to create the desired breeds that are high yielding and resistant to pests and diseases.
Cassava breeders say the local breeds are famous for their root quality, while the TME 14 is well-known for its high yields, disease and pests resistance.
The breeding process involves four stages, which include: evaluation of the seed produced between landraces and an imported variety. Cloning, where the stem of the new variety is cut into 10 pieces, planted and evaluated for uniformity in the plants.
Then there are preliminary field trials and on farm evaluations in different locations in the country.
During the trials, breeders look for strong and weak points caused by the difference in environment and the role of heterozygous in the breeding of cassava. It is common for one cassava clone to produce 10 different offsprings/varieties.
Pariyo says the institute has so far released 19 varieties, which are tolerant to Cassava Mosaic, but susceptible to CBSD.
“Our focus now is on CBS D. We are carrying out field trails and the results are promising. In the next three years, we are likely to get a resistant variety,” he notes.
Commenting on concerns that the landraces face extinction, Pariyo says all landraces have been kept in the germplasm. A germplasm is a seed bank where seeds are kept for future use.
“A breeder’s biggest asset is having a diverse germplasm,” he says.
Experts say there are a number of interventions that farmers can put in practice. First, planting clean seedlings would increase yields by 13% and improving soil fertility would push it by 17%.
Others are control of pests and diseases, which improves yields by 16%, control of soil erosion by 11% and weeding by 9%. They also say intrinsic yield potential where the role of the breeder is paramount accounts for 19%.
Pariyo says with good management practices, farmers can harvest between 30-40 tons per hectare against the current national average of 14 tons as reported by the Food and Agricultural Organisation.
He says about 60% of farmers are now planting improved cassava varieties.
Pariyo recommends planting seedlings one metre apart for optimum performance.
Cassava takes between 10-12 months to mature.
According to ASARECA, an agricultural research association in Eastern and Central Africa, about 80% of Ugandans depend on cassava for their livelihood. Cassava is the second staple food after maize in Africa.
New cassava varieties give farmers hope