Taxonomic study of entomopathogenic nematodes (Nematoda : Steinernematidae, Heterorhabditidae) from Benin

A study on the biodiversity of entomopathogenic nematodes was conducted during 2010 and 2011 in South Benin. Soil samples from eight sites production of annual and perennial crops were analysed. We obtained 13.21 % of positive soil samples out of 280. We here report on the identification of six of these isolates. Molecular, morphometrical and morphological observations classified the isolates within the genus Heterorhabditis ; one isolate was conspecific with H. indica and two other isolates with H. sonorensis. More information is needed for effective identification of the remaining three isolates. Phylogenic analysis based on sequences of ITS regions of rDNA grouped our isolates with H. sonorensis and H. taysearae with bootstrap support values of 94 and 99 % in Maximum Parsimony and Neighbour Joining trees, respectively. Morphological characters of the infective juveniles and males did not correspond to those of H. taysearae, but were close to H. sonorensis. In contrast, the female of the H. sonorensis populations did show some minor differences with the originally described one. No progeny was obtained from the crossbreeding of Beninese isolates and H. taysearae. Crossing with an isolate of H. sonorensis would have been more conclusive, but no isolates were available even for specimen’s morphological comparison.Keywords : Survey, identification, Molecular, cross-hybridization, Heterorhabditis.Etude taxonomique desnematodes entomopathogenes (Nematoda : Steinernematidae, Heterorhabditidae) du BeninUne étude diagnostique réalisée sur les nématodes entomopathogènes (NEP) en 2010 et 2011 dans le Sud- Bénin sur huit sites de production de cultures annuelles et pérennes a conduit à 13,21 % d’échantillons de sols positifs sur 280. Le présent travail a porté sur l’identification de six des isolats de NEP extraits. Les études moléculaires, morphologiques, morphométriques et d’hybridation effectuées utilisant les stades développementaux des nématodes ont révélé un isolat d’H. indica, deux d’H. sonorensis. Pour les autres isolats, des informations complémentaires sont nécessaires pour une identification complète. Le séquençage et l’analyse phylogénétique de la région interspécifique de l’ADN ribosomal ont groupé nos isolats avec H. sonorensis et H. Taysearae dans les arbres de parcimonie maximale et de Neighbour Joining avec les supports respectifs 94 et 99 %. Les caractères morphologiques des juvéniles infectieux et des mâles ne correspondent pas à ceux de la première description d’H. taysearae, mais sont proches d’H. sonorensis. Cependant, certaines femelles avec bouchon copulatoire ne correspondent pas à H. sonorensis. Nos isolats n’ont pas été féconds avec H. taysearae. Un croisement avec H. sonorensis population type serait plus concluant, mais il n’y avait aucun isolat disponible dans la base de gènes.Mots-clés : Etude, identification, moléculaire, hybridation-croisée, Heterorhabditis

Behaviour and Population Dynamics of Entomopathogenic Nematodes Following Application

Entomopathogenic nematodes (EPN) of the genera Steinernema and Heterorhabditis are widely used in inundative biological pest control programmes. It has long been recognised that increased understanding of the ecology of EPN is important for better predictions of field performance and environmental risk (Ehlers & Hokkanen, 1996; Gaugler, Lewis, & Stuart, 1997). Increasingly, EPN are also finding a place as model organisms for fundamental studies in behavioural ecology and evolutionary biology (Campos-Herrera, Barbercheck, Hoy, & Stock, 2012). In this chapter, I consider the fate of EPN used in biocontrol, focussing largely on inundative application to soil. The aim is to provide an overview of the transformation of a biotechnological product to an ecological entity, rather than a review of this rather broad topic. There are already several extensive reviews relevant to the subject, including EPN behaviour and their fate in soil (e.g. Griffin, 2012; Kaya, 2002; Lewis, Campbell, Griffin, Kaya, & Peters, 2006; Stuart, Barbercheck, Grewal, Taylor, & Hoy, 2006; see also Chap. 4). It should be noted that, while the concept of this chapter is to follow the fate of commercially produced EPN when applied to soil, many of the laboratory studies cited have used nematodes produced in insects rather than taken from commercial formulations