In 1971, Dr S.K. Hahn arrived in the IITA campus in Ibadan to establish a Root and Tuber Improvement Program. However, he was greeted by the problem of the cassava mosaic virus disease (CMV). The disease is spread mostly through the planting of infected stem cuttings or by the whitefly vector Bemisia tabaci (Genn.). The disease results in smaller yields to no yield at all due to the characteristic chlorosis in the leaves caused by CMV. Losses due to CMV have been estimated at between 12 and 23 million tons, equivalent to around 15 to 25 percent of production.
Hahn recognized the impossibility of increasing yields through his research until the CMV disease was solved. Thus, he focused his research mainly on solving this problem.
Hahn and his team found mosaic-resistant populations developed by A.J. Storey in East Africa nearly 30 years beforehand, as well as those of Brian Beck in the 1950s at Moor Plantation in Ibadan. However, these populations had very poor root yields. The team brought in germplasm from Asia and South America. With the help of Audrey Howland, the team was able to incorporate their desired level of resistance into “elite” IITA cassava breeding materials.
Ortiz, Rodomiro, compiler. 2017. IITA: 50 years after. International Institute of Tropical Agriculture (IITA), Ibadan, Nigeria