Occurrence of Plant Parasitic Nematodes and Factors That Enhance Population Build-up in Cereal-based Cropping Systems in Uganda

Plant parasitic nematodes remain a major challenge to crop production that has hitherto received minmum research attention in sub-Saharan Africa. This paper gives the diversity of nematode genera and species associated with cereal crops and indicates the possibility of nemadode population build up due to production intensification especially in soils with high sand content. Twenty-two nematode species from 10 genera of plant parasitic nematodes were recovered in root samples collected from 5 cereal crops (barley, maize, millet, sorghum and wheat) collected from 293 sites in five major cereal growing areas of Uganda (230 maize samples, 18 millet samples, 21 sorghum samples, 18 wheat samples and 6 barley samples), grown singly or as intercrops. Of these, 12 nematode species were encountered in maize roots, namely Aphelenchoides arachides, Aphelenchoides eltaybi, Ditylenchus spp, Helicotylenchus dihystera, Meloidogyne spp., Pratylenchus brachyurus, Pratylenchus goodeyi, Pratylenchus zeae, Scutellonema brachyurus, Scutellonema paralabiatum, Scutellonema clathricaudatum and Rotylenchulus borealis. Based on populations of the nematode species recovered, four distinct nematode groupings were observed: those that were widespread and abundant (Pratylenchus zeae and P. brachyurus); those that were widespread but less abundant (Scutellonema spp., Meloidogyne spp., Rotylenchulus spp. and Helicotylenchus spp.); those that were localized but very abundant (Pratylenchus goodeyi), and those that were localized but less abundant (Aphelenchoides spp. and Ditylenchus spp.). Intensified maize cropping systems with/without noncereal rotations increased risk of Pratylenchus zeae, Scutellonema spp. and Helicotylenchus spp. infection of maize.