Abstract

The response of crops to heavy metals is important to plant breeders working on marginal environments. Environmentalists need such knowledge for environmental quality assessment. Consequently, a study was carried out to determine the effect of heavy metals (Cd, Ni and Pb) stress on cassava in a greenhouse. The treatments comprised five improved cassava varieties (TME 419, TMS 98/0505, TMS 98/0510, TMS 98/0581 and TMS 97/2205), three heavy metals (Cd, Ni, Pb) and four heavy metal application rates (0, 100, 200 and 300 mg kg^-1). Heavy metals Cd, Ni and Pb reduced cassava sprouting at four weeks after planting (WAP). The stem girth, root length, root weight and dry matter yield of cassava were also negatively affected by the heavy metals at 12 WAP. The extent of the influence of the heavy metals on cassava was found to be dependent on the specific heavy metal and cassava variety. Generally, the ability of the heavy metals to affect the growth indices studied was found to be in the order: Ni > Cd > Pb. Of the five improved cassava varieties studied, TMS 98/0505 was found to be the most tolerant to the three heavy metals combined.

Key words: Cassava, nickel, cadmium, lead, effect, pollution.