Seed inoculation with beneficial rhizobacteria affects European corn borer (Lepidoptera: Pyralidae) oviposition on maize plants

Abstract

Larvae of Ostrinia nubilalis (Hübner) cause significant damage to maize ears and reduce market value of fresh sweet corn. Females rely on volatile cues to locate and oviposit preferentially on maize plants. In addition, oviposition behavior of females is influenced by soil management practices as they usually lay more eggs on maize plants grown on conventional soil than on organic soils that harbor rich microbial diversity. Since some plant growth‐promoting rhizobacteria (PGPR) are known to mediate plant health via suppression of soil pathogens and enhanced uptake of nutrients; we hypothesized that inoculation of maize seeds with PGPR will alter emission of maize volatile and reduce the attractiveness of plants to ovipositing O. nubilalis. Plants treated with the single PGPR strain Bacillus pumilus INR‐7, two PGPR mixtures (Blend‐8 or Blend‐9) or untreated plants were presented to O. nubilalis females in oviposition choice bioassays. Headspace volatile organic compounds (VOCs) from the plants were analyzed by gas chromatography–mass spectrometry (GC–MS). Ostrinia nubilalis laid significantly fewer eggs on PGPR‐treated plants compared to untreated plants. In two‐choice oviposition experiments, significantly higher numbers of eggs were laid on untreated plants compared to PGPR‐treated plants. PGPR‐treated plants emitted fewer VOCs than untreated plants which, in part, explains the relatively fewer eggs on PGPR‐treated plants. These results indicate that selected PGPR treatments can alter maize plant volatiles with important ramifications for plant‐insect interactions. The implication of this finding is discussed in the context of integrated management of soil health to improve crop resistance to biotic stressors.

Additive and heterozygous (dis)advantage GWAS models reveal candidate genes involved in the genotypic variation of maize hybrids to Azospirillum brasilense

“…Some studies show modulation of the induction and emission of plant volatiles by plant-associated microorganisms, including PGPBs and Rhizobia [85,86]. In turn, these chemicals have an important role, especially on the induction of resistance in plants against insects and pathogens [87,88]. We found the Zm00001d046604 candidate gene (additive model) corresponding to (Z)-3-hexen-1-ol acetyltransferase.…”

The Role of Plant-Associated Microbes in Mediating Host-Plant Selection by Insect Herbivores

“…For instance, in tomato, root endophyte colonization quantitatively reduced VOC production-except for trans-β-caryophyllene, which plants produced in higher quantities when associating with endophytes-and resulted in increased cotton bollworm oviposition on endophyte-associated plants [45]. In contrast, PGPR association modified the VOC profile of maize plants, suppressing production of (E)-5-methyl-2-methylene-2-hexen-1-ol and decreasing European corn borer oviposition [54]. Foliar endophytes in perennial ryegrass also deterred host selection in female African black beetles, increasing 2-ethyl-1-hexanol acetate and decreasing dodecane emissions [51].…”

Differential effects of the rhizobacterium Pseudomonas simiae on above‐ and belowground chewing insect herbivores

“…Generally, rhizobacteria-triggered ISR has adverse effects on insect herbivores, specifically on chewing insects that mainly trigger the JA defence signalling pathway (Berendsen et al, 2012;Pineda et al, 2010). Nevertheless, there are examples where rhizobacterial colonization does not influence insect attackers (Disi et al, 2018) or even favours insect performance (Boutard-Hunt et al, 2009;Megali et al, 2014;Pineda et al, 2012).…”