Studies on the interaction between tropical nematophagous fungi and entomopathogenic nematodes (Rhabditida) under laboratory conditions

Abstract

HIGHLIGHTS • Arthrobotrys AM4 and Arthrobotrys sp. CO7 were the most aggressive tropical fungi tested against Heterorhabditis LPP30 . • Water agar medium provided the best conditions to test nematode - fungus interaction with lowest environmental impact among the six media tested . • H . indica LPP30 was more apprehended than S . carpocapsae All by both tropical fungi tested . • In a soil environment , there was a repellent action from Arthrobotrys sp . CO7 against S . carpocapsae All . ABSTRACT : This study settles a step toward to understanding the interaction between nematophagous fungi (NFs) generally found in the soil and entomopathogenic nematodes (EPNs) used in the control of agricultural pests . There are very few studies linking EPNs and their natural enemies around the world and none in Brazil . Therefore , we decided to test differences regarding aggressiveness and susceptibility among the fungi and EPNs found and used in this country . The aim of this work was to study the interactions between the tropical native NFs , Arthrobotrys oligospora AM2 , Arthrobotrys AM4 , Arthrobotrys sp . CO7 , Arthrobotrys sp . CC7 and the EPNs , Heterorhabditis indica LPP30 (Heterorhabditidae) , a native nematode , and Steinernema All (Steinernematidae) , a exotic nematode , under laboratory conditions . The interaction was studied in four aspects : 1) NF aggressiveness against EPNs ; 2) effect of culture medium on NF aggressiveness to infective juveniles (IJs) ; 3) EPN susceptibility to NFs ; and 4) dispersion of IJs in two types of soil in the presence of NFs . The fungi A . musiformis AM4 and Arthrobotrys sp . CO7 were considered the most aggressive among the tested strains , since they trapped more IJs . Water agar medium provided the best conditions to test nematode - fungus interaction among the six media tested , since the fungi tested produced more trapping structures to apprehend IJs on it . Both fungi were considered very aggressive to EPNs due to their apprehension capacity . Regarding susceptibility , H . indica LPP30 IJs were more susceptible than IJs of S . carpocapsae ALL to both A . musiformis AM4 and Arthrobotrys sp . CO7 in the first 24 h of contact . However , after 48 h , the means of IJs captured by the fungi became statistically equal , except for S . carpocapsae All in Assay 2 , which presented the highest mean capture rate . The fungus Arthrobotrys sp . CO7 repelled S . carpocapsae All IJs in sand at 15 cm . The more we learn about biotic factors that interfere in biocontrol , the more effective we can make it . Future studies will focus on the characterization of these interactions in the field under tropical conditions . Keywords : Arthrobotrys , Arthrobotrys , Steinernema All , Heterorhabditis LPP30 , aggressiveness , repulsion , culture media . Cite as Arêdes A , Ribeiro LP , Dias VM , Dolinski C . Studies on the interaction between tropical nematophagous fungi and entomopathogenic nematodes (Rhabditida) under laboratory conditions . Nematoda . 2017 ; 4 :e112016 .