The development of a high-yielding Striga-tolerant maize variety is close to fruition, according to scientists at the International Maize and Wheat Improvement Centre (CIMMYT).
Common in western Kenya and regions west of the Rift Valley, Striga Hermonthica (witchweed), a semi parasitic weed, affects cereals and that can lead to a yield loss of up to 100 per cent.
It mainly attacks maize, sorghum and millet and is a serious weed in Kakamega, Busia, Homa Bay and Migori counties.
The purple-flowered weed looks harmless, but sucks nutrients from crops such as maize and sorghum, leaving farmers counting huge losses.
The weed, which thrives in poor soils with low rainfall, is prevalent in farming systems with poor crop management practices, and in communities where farmers use minimal or no fertiliser.
Once maize begins germinating in Striga-prevalent soil, it stimulates its seeds to germinate and attach themselves to the roots of the host plant, sapping nutrients and , causing stunting.
Researchers have been working to breed native resistance to the weed. This means developing seeds that are naturally resistant to Striga. This reduces the need for herbicides.
The early indication is that there are several parental lines showing the potential to tolerate or resist Striga, and these are being used to develop hybrids.
The hybrids, which offer multiple benefits for farmers, are under wide scale testing in Kenya.
“In our tests, we’re not just looking for Striga resistance, but also important traits such as good yields under optimal conditions. Others are drought stress, and low soil fertility, as well as resistance to common diseases including Leaf spot, blight, Maize streak virus (MSV) and ear rots,” said Dr Dan Makumbi, a maize breeder with the International Maize and Wheat Improvement Centre (CIMMYT). He is leading research efforts on the witchweed.
Previous control measures have involved crop rotation or intercropping with legumes such as beans, soybean or groundnut that restrict Striga’s germination.
In Kenya, researchers have also recommended a combination of herbicides as well as maize varieties tolerant to Striga be intercropped with legumes.
However, Striga persists as a serious crop husbandry issue in western Kenya, eastern Uganda, and Tanzania’s lake zone.
“While crop rotation with soybean or beans may break the cycle of Striga, its seed can stay in the soil and remain viable for up to 10 years,” Dr Makumbi notes.