Abstract:
Yams (Dioscorea spp.) are food crops of growing significance in sub Saharan Africa. Unfortunately, nematodes
are major pests to their production. A study was undertaken in major yam growing areas of Uganda to
investigate the association of plant parasitic nematodes with damage symptoms. Nematodes were assessed from
tubers, roots and surrounding soil for seven cultivars belonging to Dioscorea alata, D. bulbisiana, D. burkilliana
and D. cayenensis at harvest. Pratylenchus sudanensis was found in the greatest density and was followed by
Meloidogyne spp. Higher densities of both nematodes were observed in the tubers rather than roots. Although
symptoms of cracking and galling were relatively low, P. sudanensis incidence was strongly associated with
cracking and Meloidogyne spp. with galling. Pratylenchus sudanensis and Meloidogyne spp. incidence their
associated damage were, however, negatively correlated, suggesting inter-species competition. Principal components analysis of data suggested that differences in susceptibility to P. sudanensis occur between yam cultivars
and species.