Key words Bacterial blight. Cassava. Disease

Xanthoinonas axonopodis pv. manihotis (Xam), is a ma-jor disease of cassava (Manihot esculenta Crantz) in Af-rica and South America. Planting resistant varieties is the preferred method of disease control. Recent genetic map-ping of an F, cross (TMS 30572 x CM 2177-2) led to the construction of the first molecular genetic map of cassava. To better understand the genetics of resistance to CBB, we evaluated individuals of the F, cross for CBB resistance by controlled greenhouse inoculations and visually assessed symptoms on days 7, 15, and 30 days after inoculation, using a scale where O = no disease and 5 = maximum susceptibility. Five Xam strains were used: CIO-84, CIO-1, CIO-136, CIO-295, and ORST X-27. Area under the disease progress curve (AUDPC) was used as a quantitative measure of resistance in QTL analysis by single-marker regression. Based on the AUDPC values, eight QTLs (quantitative trait loci), lo-cated on linkage groups B, D, L, N, and X of the female-derived framework map, were found to explain 9-20% of the phenotypic variance of the crop’s response to the five Xain strains. With the male-derived framework map, four QTLs on linkage groups G and C explained 10.7-27.1 % of the variance. A scheme to confirm the usefulness of these markers in evaluating segregating populations for resistance to CBB is proposed