by Joseph Maina
At the Kenya Agricultural and Livestock Research Organization (KALRO) center in Mtwapa, Kenya, scientist Paul Kuria uproots two sets of cassava tubers exposed to the devastating cassava brown streak disease (CBSD).
One of the plants is a conventional cassava variety that has no immunity to the disease. The second has been genetically modified (GM) to resist the disease. Kuria punctiliously slices each of the tubers open, and the difference between the two is stark — like night and day.
The conventional tuber looks emaciated and is punctured with brownish, unsavory spots dotting the entire circumference of its flesh. The GM tuber, on the other hand, is the picture of good health. Its skin is flawless and firm, and its flesh has an impeccable, white lustre.
CBSD is considered one of the world’s most dangerous plant diseases due to its significant impact on food and economic security. Cassava varieties that are resistant to the disease could considerably improve the crop’s ability to feed Africa while generating income for smallholder farmers.
In severe cases, the disease can lead to 100 percent yield loss. As noted by KALRO and its partners, cassava resistant to CBSD is in high demand by farmers where the crop is grown.
Meeting that demand has been an elusive target for plant breeders. But through modern biotechnology, a collaborative effort known as the VIRCA project has developed CBSD-resistant cassava line 4046. It has the potential to prevent 90 percent of crop damage, thus improving the yield and marketability of cassava roots.
“We used genetic engineering and produced an improved cassava,” Professor Douglas Miano, the lead scientist in the project, told journalists and farmers who toured the KALRO grounds in Mtwapa in early August.
“It’s the first GM cassava in the world, and Kenya is leading in this production,” Miano said.
The VIRCA (Virus Resistant Cassava for Africa) project was conceived in 2005 with the aim of solving the viral diseases that suppress cassava yields and reduce farmer incomes in East Africa. It brings together KALRO, the National Agricultural Research Organization (NARO) of Uganda and the Donald Danforth Plant Science Centre (DDPSC) in the United States.
“We have two main diseases affecting cassava production — CBSD and cassava mosaic disease,” Miano explained. “Cassava mosaic disease affects the leaves of the crop. The net effect is a reduction in the amount of cassava that is produced. CBSD, on the other hand, destroys the roots and affects the tuber.”