DISEASE EXPRESSION IN PLANTS DERIVED FROM CASSAVA CUTTINGS WITH DIFFERENT LEVELS OF INFECTION WITH AFRICAN CASSAVA MOSAIC-VIRUS

In the field, three symptom-types of African cassava mosaic virus infe ction are recognized in the cassava variety TMS4 (2) 1425, namely symp tomless, partially symptomatic, and fully symptomatic plants. Main ste m cuttings developed into plants with a significantly higher disease i ncidence than primary branch cuttings, particularly when derived from partially symptomatic plants in which one of the primary branches was healthy. Approximately a 10% disease incidence was observed in plants which developed from main stem cuttings of symptomless plants while th ose from primary branch cuttings remained healthy. Apart from symptoml ess plants, the reduced tendency of healthy branches of partially symp tomatic plants to show reversion permits them to serve as potential so urces of healthy cuttings.