First record on the distribution of entomopathogenic nematodes (Rhabditida: Steinernematidae and Heterorhabditidae) in Southern Benin.

Abstract

For the first time, surveys of entomopathogenic nematodes (EPN) were conducted in five departments in the Guinean zone of Southern Benin. Out of 84 prospected sites and 280 collected soil samples from agricultural and natural vegetation, 26 (31.0%) and 32 (11.4%) were positive for EPN, respectively. Identification of the EPN was based on analyses of sequences of the ITS rDNA region and morphological/morphometric investigations. Two species were found, Heterorhabditis sonorensis and H. indica. This is the first record of H. sonorensis since its description from the Sonora desert in Mexico. Heterorhabditis sonorensis was the most common species, showing a preference for semi-closed habitats such as citrus orchards, other fruit production fields and woodland with soils having sand and organic matter content ranging between 53.6-89.5% and 0.1-4.7%, respectively, and a pH from acidic (4) to neutral (7.1). Entomopathogenic nematodes were not recovered from crop fields (maize, cassava, groundnut and bean) and soil samples with less than 50% sand content. Heterorhabditis indica was associated with citrus orchards and fruit fields on sand to sandy clay soils, with pH slightly acidic (pH = 5.4-6.4), but not with woodland. Discriminant analysis identified five major environmental variables, longitude, organic matter content and texture (silt, sand and clay content) to be the most important abiotic factors detemining the occurrence of EPN in soil from Southern Benin. Using these parameters, redundancy analysis revealed that H. sonorensis and H. indica prefer soils with high sand or organic matter content located in the more eastern longitude. No significant difference was observed in EPN species preferences taken individually, in terms of studied ecological parameters.