Occurrence, abundance and distribution of plant-parasitic nematodes associated with rice (Oryza spp.) in different rice agroecosystems in Togo
Rice is the second most important cereal in Togo. Among constraints that affect rice production, plant parasitic nematodes are of great importance. The objective of this study was to determine the distribution, abundance and frequency of plant nematodes in different agroecological zones of Togo. A total of 50 composite soil and root samples (25 each) were taken from 25 fields (5 per zone) randomly selected from the five agroecological zones. Nematodes were extracted from 100 ml soil and 1g fresh root samples using the Hermann techniques. Nematodes were then fixed and mounted on slide and identified to genus level using identification keys. The survey documented twelve plant-parasitic nematode genera among which ten, (Hirschmanniella spp., Meloidogyne spp., Xiphinema spp., Scutellonema spp., Helicotylenchus spp., Heterodera spp., Criconema spp., Pratylenchus spp., Trichodorus spp. and Tylenchid spp.), were recorded from lowland, two (Helicotylenchus and Scutellonema) from upland and five (Dolichodorus spp., Helicotylenchus spp., Tylenchorhynchus spp., Scutellonema spp. and Xiphinema spp.), from flooded ecosystem. Hirschmanniella spp., Meloidogyne spp and Helicotylenchus spp. were the most frequent and abundant plant-parasitic nematode genera recorded from more than 71% of the samples. Helicotylenchus spp., Hirschmanniella spp., Meloidogyne spp. and Scutellonema spp., were recorded in both soil and root samples while Pratylenchus spp., Heterodera spp. and Tylenchorhynchus spp., were found to be associated to root and Trichodorus spp., Tylenchid spp., Xiphinema spp., Criconema spp. and Dolichodorus spp., were recorded from soil samples only. The high diversity of nematode genera recorded in the survey is attributed to the rice ecosystem, which is mostly characterized by lowland ecosystem with intensive cropping. This study established the evidence that nematodes could be important constraints for rice production, suggesting further research focusing on their damage potential and development of effective rice nematode management strategy for sustainable rice production in Togo.
Keywords: plant parasitic nematode, abundance, occurrence, rice ecosystem, distribution.