Development of cassava (Manihot esculenta Crantz) cultivars for resistance to cassava mosaic disease in Zambia.

Evaluation of cassava cultivars for CMD resistance was conducted in 2009/2010 and 2010/11 seasons at Mansa Research Station in Luapula province using a 4 x 4 α lattice design.Both introduced and locally grown cultivars had significant (P<0.001)differences in their reaction to CMD.Bangweulu, Namuyongo, Kalaba, Chikula, Mwakamoya, Chila7 and Chila11 were the most susceptible genotypes.Mweru, Tanganyika, and Nalumino were moderately tolerant to CMD.Eight hundred F 1 genotypes developed using a North Carolina II mating design were evaluated in a 4 x 5 α lattice design in 2011 at Mansa Research Station, Luapula province to determine combining ability for reaction to CMD, yield and yield components.The plants were harvested 7 months after planting (MAP).Significant (P<0.001) general combining ability and specific general combining ability were recorded for CMD.The SCA effects were more important for CMD than GCA effects suggesting that non-additive gene action was more prominent than the additive gene action in determining CMD reaction.Parent lines with desired significant, negative GCA effects for reaction to CMD were Bangweulu, Kampolombo, Nalumino and TME2.In general, the survey and participatory rural appraisal established CMD as one of the constraints to cassava production and created a basis for the research study.The findings indicate opportunities that exist in creating genotypes with tolerance to CMD.The study identified cassava lines with resistance to CMD.The lines that expressed the above trait should be selected and tested further for release to the farmers in Zambia.Since the clonal evaluation trial was harvested at 7 MAP, there is need to investigate further for earliness trait in best performing lines in different locations.