afrol News, 8 August - Agricultural scientists have made a breakthrough in the fight against deadly witch-weed, which has been a stumbling block for high yields for many sub-Saharan staple producers.

According to International Crops Research Institute for the Semi-Arid Tropics (ICRISAT), researchers have successfully identified and transferred genes that confer resistance to Africa's most deadly weed (Striga) using the novel marker assisted selection technique successfully for the first time in the history of crop breeding in Africa.

ICRISAT reports that researchers have managed to confer resistance to Striga in sorghum, overcoming a barrier that has for decades held back scientists' efforts to protect key food crops such as sorghum, millet, maize and rice. These crops are primary food sources for 300 million people across sub-Saharan Africa.

Striga (Striga hermonthica), also known as witchweed, is said to destroy between 40 to 100 percent of a complete season's crop, with its annual crop damage across Africa estimated at seven billion dollars (US$7 billion). "Every year Striga weed attacks and kills Africa's most important food crops in more than 40 million hectares of farmland often leaving farmers with no harvest," said ICRISAT in a statement.

Currently, the weed threatens to wipe out cereal crops in most of Western Kenya and Eastern Uganda, national agricultural research institutes in the two countries have warned.

Africa's resource-poor farmers manage Striga primarily by weeding, a pointless, back-breaking activity which comes too late, says ICRISAT, explaining that by the time the crop sprouts, the weed, whose seeds reside in the soil, has long-since attached to plant roots and begun sapping off plant nutrients in earnest. It further explained that Striga is a prolific seed producer, whose seeds lie dormant in the soil for up to two decades.

"Scientists have searched for the solution to Striga damage using a variety of methods, but without much success," says Dr Dionysious Kiambi, a molecular geneticist with ICRISAT.

"Through marker assisted selection, we have determined the precise segments of the sorghum genome known to confer Striga-resistance and have transferred them to farmer-preferred varieties through conventional breeding with very promising results".

Marker assisted selection is a new technique which entails use of genetic landmarks to tag and transfer specific genes or group of genes that control characteristics of interest such as improved crop productivity, resistance to diseases or pests, or tolerance to stresses like floods and drought. This is the first time the technology has been used successfully for crop improvement in Africa, according to ICRISAT.

ICRISAT has been collaborating with scientists from University of Hohenheim in Germany and national agricultural research institutes of Eritrea, Kenya, Mali and Sudan. The team has to date created five Striga-resistant sorghum varieties whose initial trials on-station have been able to ward off Striga attacks, some as effectively as the donor parent, sorghum N13. In Kenya, Mali and Sudan, scientists are currently testing the new witchweed-resistant varieties in farmer fields.

Researchers in Africa have for decades experimented with a number of "potentially successful" techniques for managing this deathly weed including breeding for Striga tolerance in various crops, promotion of rotational cropping of cereals with legumes such as groundnuts, cowpeas and soybean in order to break the weed's breeding circle, as well as the use of biological and herbicidal control methods.

"If the on-station results are successfully replicated on-farm, Africa's biggest cereal crop menace - Striga - may well be reigned in, boosting agricultural production, food security and farmer incomes across the continent," concluded ICRISAT in a statement today.

By staff writer

© afrol News

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