New genotyping rescues old phenotypes: beneficial traits in Heterorhabditis bacteriophora wild type material and association to single nucleotide polymorphisms

Abstract

The entomopathogenic nematode (EPN), Heterorhabditis bacteriophora, is a biocontrol agent with almost world-wide distribution, thus providing a huge source of biodiversity available for exploitation in breeding programmes to improve beneficial traits. For management of economically important insect pests, the nematode is mass-produced in liquid culture, formulated with inert carriers, and transported under controlled temperature conditions to maintain its quality. The biocontrol potential of nematode materials is defined by their genetic background. Previous reports have assessed the phenotypic plasticity of H. bacteriophora. Major beneficial traits are field efficacy influenced by their virulence, longevity and field persistence and tolerance to abiotic stresses like oxidative stress, desiccation and extreme low and high temperatures. For several of these traits high heritability values (h2) have been reported, providing a platform for trait improvement by selection. Modern breeding uses molecular markers to track beneficial traits. Recent studies reported hundreds of single nucleotide polymorphisms (SNPs) in H. bacteriophora. This investigation revived a large set of cryopreserved wild types, hybrids and phenotyped materials of H. bacteriophora. Additional phenotypic data on the virulence (LC50) of H. bacteriophora strains against mealworm (Tenebrio molitor) were produced ranging from 1.4 ± 0.3 to 8.0 ± 3.6 nematodes per insect. Markers linked to beneficial traits were used for a comprehensive genotype analysis transferring reported SNP sequence information into the multiplex platform SeqSNP. Specific alleles associated to beneficial traits were identified and 65 materials were classified for the presence of relevant SNPs associated to beneficial traits. This information provides a valuable platform for exploitation of the nematode’s biodiversity for future breeding and selection approaches.