EARLY SCREENING OF CASSAVA FOR RESISTANCE TO ROOT-KNOT NEMATODES

A method was developed for early screening of cassava for resistance t o root-knot nematodes. One-node cassava cuttings were planted in plast ic disposable beverage cups filled with sterile 1:1 (by volume) sand-s oil mixture. Two weeks after planting, the plantlets were infested wit h a 10 mi suspension containing approximately 1 000 Meloidogyne spp. e ggs. One month after inoculation, the cassava root systems were evalua ted for damage and rated for gall index. Densities of Meloidogyne fema les in the roots were established by differential staining, followed b y counting of the female root-knot nematodes under a stereomicroscope. Significant differences in gall index and number of established femal es, but not in reduction in fresh root weight, were observed among var ieties. While some confirmatory field surveys are still required, find ings from preliminary surveys carried out in two areas of Uganda sugge st that the relative susceptibility of a variety in the field can adeq uately be predicted by using one-node cuttings.