Nematode communities associated with papaya in Kenya: first report of Meloidogyne javanica and description of soil health in papaya fields

Abstract

Background Plant-parasitic nematodes (PPNs) are major pathogens of fruit trees globally, causing substantial economic losses. In Kenya, research on papaya has focused primarily on viral diseases, particularly those caused by papaya ringspot virus, with no previous reports of PPNs occurrence. Objectives This study aimed to characterise the diversity of PPNs and FLNs in papaya fields in Elgeyo-Marakwet County, Kenya, and to assess the associated soil health status. Special emphasis was placed on evaluating FLNs as bioindicators of soil health. Methods Using the Baermann tray method, nematodes were extracted from 64 composite root and soil samples collected across 12 papaya fields in Elgeyo-Marakwet County. PPNs were identified to the genus level, with root-knot (RKN) Meloidogyne species identified by comparing their sequences with reference sequences and analysed using the PPNID tool. The FLNs were classified to the family level and analysed using NINJA software to assess soil health. Results Four PPN genera and six FLN families were identified, with Meloidogyne javanica being the only RKN, representing the first PPN report in papaya in Kenya. This raises concerns about potential interactions between M. javanica and viral pathogens, which could increase the incidence and severity of papaya ringspot disease. Metabolic footprint stress diagram analyses revealed fertile, mature soils capable of regulating opportunistic organisms, including PPNs. Conclusion Understanding soil health and nematode composition is essential for developing sustainable nematode management strategies to increase papaya yields