No fitness cost for wheat's H gene-mediated resistance to Hessian fly (Diptera: Cecidomyiidae)

Resistance (R) genes have a proven record for protecting plants against biotic stress. A problem is parasite adaptation via Avirulence (Avr) mutations, which allows the parasite to colonize the R gene plant. Scientists hope to make R genes more durable by stacking them in a single cultivar. However, stacking assumes that R gene-mediated resistance has no fitness cost for the plant. We tested this assumption for wheat's resistance to Hessian fly, Mayetiola destructor (Say) (Diptera: Cecidomyiidae). Our study included ten plant fitness measures and four wheat genotypes, one susceptible, and three expressing either the H6, H9, or H13 resistance gene. Because R gene-mediated resistance has two components, we measured two types of costs: the cost of the constitutively-expressed H gene, which functions in plant surveillance, and the cost of the downstream induced responses, which were triggered by Hessian fly larvae rather than a chemical elicitor. For the constitutively expressed Hgene, some measures indicated costs, but a greater number of measures indicated benefits of simply expressing the H gene. For the induced resistance, instead of costs, resistant plants showed benefits of being attacked. Resistant plants were more likely to survive attack than susceptible plants, and surviving resistant plants produced higher yield and quality. We discuss why resistance to the Hessian fly has little or no cost and propose that tolerance is important, with compensatory growth occurring after H gene-mediated resistance kills the larva. We end with a caution: Given that plants were given good growing conditions, fitness costs may be found under conditions of greater biotic or abiotic stress.     

Does R gene resistance allow wheat to prevent plant growth effects associated with Hessian fly (Diptera: Cecidomyiidae) attack?

Resistance genes (R genes) are an important part of the plant's immune system. Among insects, the Hessian fly, Mayetiola destructor (Say) (Diptera: Cecidomyiidae), larva is the target of the greatest number of characterized R genes (H1-H32). The biochemical/molecular mechanism of R gene resistance to Hessian fly is not well understood. In the absence of an effective R gene, larvae caused extensive growth deficits (> 30 cm) in wheat seedlings. In the presence of one of three effective R genes, H6, H9, or H13, larvae caused small growth deficits (approximately 3-4 cm) in two leaves (third and fourth) that were actively growing during the first days of larval attack. After larvae died on R gene plants, the fifth leaf and tiller leaves exhibited small increases in growth (2-4 cm). Growth responses of susceptible and resistant plants diverged at a time when Hessian fly larvae were establishing a nutritive gall tissue at feeding sites. The results of this study support the hypothesis that R gene resistance cannot prevent initial larval attack, but, by stopping the formation of the larval gall, it prevents the most serious consequences of larval attack.     

Effects of natural enemies on relative fitness of Heliothis virescens genotypes adapted and not adapted to resistant host plants

We investigated the potential of two natural enemies of Heliothis virescens (F.) (Noctuidae) to affect its rate of adaptation to tobacco containing Bacillus thuringiensis Berliner toxin. Larval fitness of two laboratory strains of H. virescens, one adapted to B. thuringiensis toxin and one not adapted, was compared on toxic and nontoxic plants, in the presence of the parasitoid Campoletis sonorensis (Cameron) (Ichneumonidae) or the entomopathogenic fungus Nomuraea rileyi (Farlow) Samson. By exposing larvae to plants and enemies for no more than 24 h, we focussed on the behavioral rather than physiological component of their interaction with toxic plants and natural enemies. Parasitism of H. virescens larvae by C. sonorensis during exposure periods of 1–4 h was lower on toxic plants than nontoxic plants and was lower for nonadapted larvae than for toxin-adapted larvae. Decreased larval feeding damage on toxic versus nontoxic plants, and by nonadapted versus adapted larvae, may explain differences in parasitism, because C. sonorensis locates host larvae using cues from damaged plants. Effects of plant toxicity and larval strain on H. virescens survival were numerically consistent with effects on parasitism, but they were not statistically significant. When mean larval survival is used to estimate fitness of the nonadapted genotype relative to the toxin-adapted genotype, we find that C. sonorensis is expected to delay adaptation to toxic plants. Percent infection by N. rileyi of H. virescens larvae exposed to fungus-treated plants for 24 h was greater when plants were toxic, and was greater for nonadapted larvae than toxin-adapted larvae. There were corresponding decreases in larval survival on toxic compared to nontoxic plants, and of nonadapted compared to adapted larvae. Interaction of effects of plant line and larval strain on survival was significant in the presence of fungus, but not in the absence of fungus, which indicates that the effect of toxic plants on the relative fitness of toxin-adapted and nonadapted larvae was mediated by fungus. As in the interaction with C. sonorensis, behavior of larvae on plants may explain differences in susceptibility to N. rileyi. Because nonadapted larvae moved more than toxin-adapted larvae on toxic plants, nonadapted larvae may have been more likely to encounter a lethal dose of conidia. In contrast with C. sonorensis, N. rileyi, which decreased the fitness of the nonadapted genotype relative to the adapted genotype, is expected to accelerate adaptation to toxic plants.     

Molecular genetic mapping of three X-linked avirulence genes, vH6, vH9 and vH13, in the Hessian fly.

Three X-linked avirulence genes, vH6, vH9, and vH13 in the Hessian fly, Mayetiola destructor, confer avirulence to Hessian fly resistance genes H6, H9, and H13 in wheat. We used a combination of two- and three-point crosses to determine the order of these genes with respect to each other, the white eye mutation and three X-linked molecular markers, G15-1, 020, and 021, developed from genomic lambda clones, lambda G15-1, lambda 020, and lambda 021. The gene order was determined to be vH9-vH6-G15-1-w-vH13-020-021. In situ hybridization of lambda G15-1, lambda 020, and lambda 021, on the polytene chromosomes of the Hessian fly salivary gland established their orientation on Hessian fly chromosome X1. Based on the size of the Hessian fly genome, and the genetic distances between markers, the relationship of physical to genetic distance was estimated at no more than 300 kb/cM along Hessian fly chromosome X1, suggesting that map-based cloning of these avirulence genes will be feasible.     

Expressed sequence tags from a wheat-rye translocation line (2BS/2RL) infested by larvae of Hessian fly [<Emphasis Type="Italic">Mayetiola destructor</Emphasis> (Say)]

Of the 16 known biotypes of the Hessian fly [Mayetiola destructor (Say)], biotype L is recognized as being the most virulent. We have previously reported the development of near-isogenic lines (NILs) (BC₃F_3:4) by backcross introgression (Coker797*4/Hamlet) that differed by the presence or absence of the H21 gene on 2RL chromatin. Florescence in situ hybridization analysis revealed introgressed 2RLs in NILs possessing the H21 gene, but no signal was detected in NILs lacking 2RL. As part of an approach to elucidate molecular interactions between plants and the Hessian fly, a cDNA library from NILs with H21 infested by larvae of biotype L of the Hessian fly was constructed for expressed sequence tag (EST) analysis. Of 1,056 sequenced reactions attempted, 919 ESTs produced some lengths of readable sequences. Based on their putative identification, 730 ESTs that showed significant similarity with amino acid sequences registered in the gene bank were divided into 13 functional categories. Defense- and stress-related genes represented about 16.1%, including protease inhibition, oxidative burst, lignin synthesis, and phenylpropanoid metabolism. EST clones obtained from the cDNA library may provide a clue to the molecular interactions between plant and larva of the Hessian fly larval infestation.Abbreviations ESTs Expressed sequence tags - FISH Florescence in situ hybridization - NILs Near-isogenic linesCommunicated by P. PuigdoménechAll of the EST sequence data reported will appear in the dbEST and GenBank database (accession numbers CB307016 to CB307934)     

Chromosome landing near avirulence gene vH13 in the Hessian fly.

AFLP markers in linkage disequilibrium with vH13, an avirulence gene in the Hessian fly (Mayetiola destructor) that conditions avirulence to resistance gene H13 in wheat (Triticum spp.), were discovered by bulked segregant analysis. Five AFLPs were converted into codominant site-specific markers that genetically mapped within 13 cM of this gene. Flanking markers used as probes positioned vH13 near the telomere of the short arm of Hessian fly chromosome X2. These results suggest that the X-linked avirulence genes vH6, vH9, and vH13 are present on Hessian fly chromosome X2 rather than on chromosome X1 as reported previously. Genetic complementation demonstrated that recessive alleles of vH13 were responsible for the H13-virulence observed in populations derived from four different states in the U.S.A.: Georgia, Maryland, Virginia, and Washington. Results support the hypothesis that a gene-for-gene interaction exists between wheat and Hessian fly.     

Virulence in Hessian fly (Diptera: Cecidomyiidae) field collections from the southeastern United States to 21 resistance genes in wheat

Genetic resistance in wheat, Triticum aestivum L., is the most efficacious method for control of Hessian fly, Mayetiola destructor (Say) (Diptera: Cecidomyiidae). However, because of the appearance of new genotypes (biotypes) in response to deployment of resistance, field collections of Hessian fly need to be evaluated on a regular basis to provide breeders and producers information on the efficacy of resistance (R) genes with respect to the genotype composition of Hessian fly in regional areas. We report here on the efficacy of 21 R genes in wheat to field collections of Hessian fly from the southeastern United States. Results documented that of the 21 R genes evaluated only five would provide effective protection of wheat from Hessian fly in the southeastern United States. These genes were H12, H18, H24, H25, and H26. Although not all of the 33 identified R genes were evaluated in the current study, these results indicate that identified genetic resistance to protect wheat from Hessian attack in the southeastern United States is a limited resource. Historically, R genes for Hessian fly resistance in wheat have been deployed as single gene releases. Although this strategy has been successful in the past, we recommend that in the future deployment of combinations of highly effective previously undeployed genes, such as H24 and H26, be considered. Our study also highlights the need to identify new and effective sources of resistance in wheat to Hessian fly if genetic resistance is to continue as a viable option for protection of wheat in the southeastern United States.     

Characterization of Wheat Random Amplified Polymorphic DNA Markers Associated with the H11 Hessian Fly Resistance Gene

In Tunisia, the Hessian fly Mayetiola destructor Say is a major pest of durum wheat （Triticum durum Desf.） and bread wheat （T. aestivum L.）. Genetic resistance is the most efficient and economical method of control of this pest. To date, 31 resistance genes, designated H1-H31, have been identified in wheat. These genes condition resistance to the insect genes responsible for virulence. Using wheat cultivars differing for the presence of an individual Hessian fly resistance gene and random amplified polymorphic DNA （RAPD） analysis, we have identified a polymorphic 386-bp DNA marker （Xgmib1-1A.1） associated with the H11 Hessian fly resistance gene. Blast analysis showed a high identity with a short region in the wild wheat （T. monococcum） genome, adjacent to the leaf rust resistance Lr10 gene. A genetic linkage was reported between this gene （Lr10） and Hessian fly response in wheat. These data were used for screening Hessian fly resistance in Tunisian wheat germplasm. Xgmib1-1A.1-like fragments were detected in four Tunisian durum and bread wheat varieties. Using these varieties in Hessian fly breeding programs in Tunisia would be of benefit in reducing the damage caused by this fly.     

Association of a DNA marker with Hessian fly resistance gene H9 in wheat

The Hessian fly [Mayetiola destructor (Say)] is a major pest of wheat (Triticum aestivum L.) and genetic resistance has been used effectively over the past 30 years to protect wheat against serious damage by the fly. To-date, 25 Hessian fly resistance genes, designated H1 to H25, have been identified in wheat. With near-isogenic wheat lines differing for the presence of an individual Hessian fly resistance gene, in conjunction with random amplified polymorphic DNA (RAPD) analysis and denaturing gradient-gel electrophoresis (DGGE), we have identified a DNA marker associated with the H9 resistance gene. The H9 gene confers resistance against biotype L of the Hessian fly, the most virulent biotype. The RAPD marker cosegregates with resistance in a segregating F₂ population, remains associated with H9 resistance in a number of different T. aestivum and T. durum L. genetic backgrounds, and is readily detected by either DGGE or DNA gel-blot hybridization.Purdue University, Agric. Exp. Stn. Journal paper No. 14440     

Biotypes of Hessian fly (Dipt., Cecidomyiidae) in Morocco

Hessian fly, Mayetiola destructor (Say), is the most important insect pest of wheat in Morocco, where host plant resistance has been used successfully for control. Our objective was to determine the frequency of Hessian fly virulence on H5, H13 and H22 resistance genes. Five Hessian fly populations from the principal cereal‐growing regions in Morocco were studied. The variability in percentage of susceptible plants across Hessian fly populations was highly significant (P < 0.01), indicating differences in virulence frequencies. Plants with the H13 gene had the lowest percentage of susceptible plants, 1.77 and 1.51%, when infested with Hessian flies from Fes and Marchouch, respectively. A low level of virulence to H22 was detected in Fes, Abda and Marchouch populations, 1.87, 1.54 and 1.99% susceptible plants, respectively. The level of virulence to H5 was low in all the five populations. The Beni Mellal population gave the highest percentage of susceptible plants carrying H13 and H22 genes, 6.43 and 7.28%, respectively. The size of live larvae on susceptible plants of the three cultivars carrying H5, H13 and H22 was similar to that of the susceptible check, indicating that a true virulence (biotype) is developing in Hessian fly populations in Morocco. Thus, continuous monitoring of the development of Hessian fly biotypes is essential for optimal deployment of resistance genes.     

Identification of RAPD markers for 11 Hessian fly resistance genes in wheat

 The pyramiding of genes that confer race- or biotype-specific resistance has become increasingly attractive as a breeding strategy now that DNA-based marker-assisted selection is feasible. Our objective here was to identify DNA markers closely linked to genes in wheat (Triticum aestivum L.) that condition resistance to Hessian fly [Mayetiola destructor (Say)]. We used a set of near-isogenic wheat lines, each carrying a resistance gene at 1 of 11 loci (H3, H5, H6, H9, H10, H11, H12, H13, H14, H16 or H17) and developed by backcrossing to the Hessian fly-susceptible wheat cultivar ‘Newton’. Using genomic DNA of these 11 lines and ‘Newton’, we have identified 18 randomly amplified polymorphic DNA (RAPD) markers linked to the 11 resistance genes. Seven of these markers were identified by denaturing gradient gel electrophoresis and the others by agarose gel electrophoresis. We confirmed linkage to the Hessian fly resistance loci by cosegregation analysis in F₂ populations of 50–120 plants for each different gene. Several of the DNA markers were used to determine the presence/absence of specific Hessian fly resistance genes in resistant wheat lines that have 1 or possibly multiple genes for resistance. The use of RAPD markers presents a valuable strategy for selection of single and combined Hessian fly resistance genes in wheat improvement. Received: 20 March 1996 / Accepted: 6 September 1996     

Virulence of Hessian fly (Diptera: Cecidomyiidae) in the Fertile Crescent

The Hessian fly, Mayetiola destructor (Say), is an important insect pest of wheat (Triticum spp.) in North Africa, North America, southern Europe and northern Kazakhstan. Both wheat and this pest are believed to have originated from West Asia in the Fertile Crescent. The virulence of a Hessian fly population from Syria against a set of cultivars carrying different resistance genes, in addition to other effective sources with unknown genes, was determined in the field and laboratory at the International Center for Agricultural Research in the Dry Areas (ICARDA) during the 2005/2006 cropping season. Only two resistance genes (H25 and H26) were effective against the Syrian Hessian fly population, making it the most virulent worldwide. This high virulence supports the hypothesis that Hessian fly coevolved with wheat in the Fertile Crescent of West Asia. The ICARDA screening programme is using this Hessian fly population to identify new resistance genes to this pest.     

Genotypic interaction between resistance genes in wheat and virulence genes in the Hessian fly Mayetiola destructor (Diptera: Cecidomyiidae)

The genotypic interaction between wheat resistance genes H3, H6, H7H8, H9 and virulence genes vH3, vH6, vH7vH8, vH9 of Hessian fly, Mayetiola destructor (Say), was studied in a growth chamber. Results showed that plants homozygous and heterozygous for the H3 gene expressed a high level of resistance against homozygous avirulent and heterozygous larvae carrying the vH3 virulence allele. The H7H8 genes were highly effective in the homozygous condition, but displayed a reduced level of resistance in the heterozygous condition. The H6 and H9 genes showed different levels of resistance against the reciprocal heterozygous larvae (vH6(a)vH6(A) versus vH6(A)vH6(a) and vH9(a)vH9(A) versus vH9(A)vH9(a)). Adults reared from vH6(a)vH6(A) and vH9(a)vH9(A) larvae were all males, consistent with the vH6 and vH9 X-linkage. Plants homozygous for H3, H6, H7H8, and H9 allowed for greater larval survival of heterozygous larvae, which suggests that avirulence to these resistance genes is incompletely dominant. Greater survival of homozygous avirulent larvae on heterozygous plants (H3h3, H6h6, H7h7H8h8, H9h9) suggests incomplete dominance of these wheat genes. Survival of heterozygous along with homozygous virulent larvae would reduce selection pressure for virulence in Hessian fly populations infesting fields of resistant wheat cultivars. This would be expected to slow the increase in frequency of virulence alleles that often results from deployment of resistant cultivars.     

Distribution,population dynamics and damage of Hessian fly,Mayetiola destructor (Diptera: Cecidomyiidae) in North Tunisia

A three years survey and monitoring studies (2013–2014–2015) were carried out through 4 regions of north Tunisia in order to follow the evolution of the distribution, the frequency of occurrence and damage caused by the Hessian fly Mayetiola destructor (Say) to bread wheat (Triticum aestivum L.) and durum wheat (Triticum durum Desf). Moreover, the effectiveness of resistance genes H3, H5, H6, H7, H8, H9, H10, H11, H12, H13, H14, H15, H22, H23, H25 and H26 to protect wheat from Hessian fly attack was assessed in natural field and under controlled laboratory conditions at INRAT-Kef Station. Results showed that Hessian fly was detected in 60.33% and 51.5% of all sampled durum and bread wheat fields, respectively. This pest was more frequent with a higher percentage of infestation in semi-arid regions. Indeed, during 2013, infestation rate attained 12.39% in Kef region against 0.9% registered in Bizerte region. In order to update information about the annual number of generations, we surveyed the population dynamic of Hessian fly in Kef region. Three generations of the fly were counted annually on wheat, with two complete and one incomplete generation. This insect affects host plant growth at different developmental stages. Plant height was the most affected parameter followed by shoot dry weight and tiller number. Field investigations on host resistance revealed that among the 16 tested resistance genes, and only three were strictly effective (H22, H25 and H26). The resistance genes H5, H9, H13 and H9H13 have also conferred high levels of protection against Hessian fly. This work indicated that H22, H25 and H26 genes could be incorporated into Tunisian wheat varieties and released to farmers to manage the threat due to Hessian fly attacks.     

Hessian fly Avirulence gene loss‐of‐function defeats plant resistance without compromising the larva's ability to induce a gall tissue

Plant pathogen effectors encoded by Avirulence (Avr) genes benefit the pathogen by promoting colonization and benefit plants that have a matching resistance (R) gene by constituting a signal that triggers resistance. The Hessian fly, Mayetiola destructor (Say) (Diptera: Cecidomyiidae), resembles a plant pathogen in showing R/Avr interactions. Because of these interactions, a wheat plant with the H13 resistance gene can be resistant or susceptible depending on the genotype of the larva that attacks the plant, being resistant if attack comes from a larva with a functional vH13 gene, but susceptible if attack comes from a larva with a non‐functional vH13 gene. In this study we asked: does this susceptible interaction involving plants with H13 look like susceptible interactions with plants lacking H13? Possibly, the H13 plant attacked by a larva with a non‐functional vH13 is induced to partial rather than complete resistance. Or the larva, lacking its vH13‐encoded effector, is compromised in its ability to induce susceptibility, which includes forcing the plant to create a gall nutritive tissue. Responses of epidermal cells to larval attack were explored using imaging techniques (light microscopy, scanning and transmission electron microscopy). Whole‐organism responses were investigated by measuring the growth of plants and larvae. No evidence was found for partial resistance responses by H13 plants or for a compromise in the ability of vH13 loss‐of‐function larvae to induce susceptibility. It appears that disrupting vH13 function is sufficient for overcoming the induced resistance mediated by the H13 gene.     

Biotype composition of Hessian fly (Diptera: Cecidomyiidae) populations from the southeastern, midwestern, and northwestern United States and virulence to resistance genes in wheat

Twenty-three Hessian fly, Mayetiola destructor (Say), populations collected in the southeastern (Alabama and Mississippi), midwestern (Indiana), and northwestern (Idaho and Washington) United States from 1995 to 1999 were evaluated for biotype composition based on response to Hessian fly resistance genes H3, H5, H6, and H7H8 in wheat, Triticum aestivum L. Biotypes L and O, combined, made up at least 60% of all Alabama populations. Biotype L was predominant in the northern third of Alabama and biotype O in the southern two-thirds of the state. Based on biotype data, wheat cultivars with H7H8 resistance should be highly effective in central and southern Alabama. Fifty-four percent of the Mississippi population consisted of biotype L, and the remaining virulent biotypes (B, D, E, G, J, and O) ranged in frequency from 1 to 17%. The Mississippi population also contained 4% of the avirulent biotype GP. Only biotypes D and L were found in Indiana populations, but biotype L was predominant. Hessian fly populations from Idaho and Washington contained one or more of the virulent biotypes D-H, J, and L-O; however, only biotypes E, F, and G occurred at frequencies > 12%. The avirulent biotype GP made up 25-57% of Idaho and Washington populations, a much higher percentage than found in populations from the eastern United States. Although the highest level of virulence in Idaho and Washington populations was found to resistance genes H3 and H6, the frequency of biotype GP would indicate that the currently deployed gene H3 would provide a moderate to high level of resistance, depending on location. Nine of the populations, plus populations collected from the mid-Atlantic state area in 1989 and 1996, also were tested against the wheat cultivar 'INW9811' that carries H13 resistance to Hessian fly biotype L and two Purdue wheat lines with unidentified genes for resistance. The H13 resistance in INW9811 was highly effective against all populations tested from the eastern and northwestern U.S. wheat production areas, except Maryland and Virginia. Population studies also indicated that wheat line CI 17960-1-1-2-4-2-10 likely carries the H13 resistance gene, based on the similarity of its response and that of INW9811 to eight fly populations. Continued monitoring of biotype frequency in Hessian fly populations is required for optimal deployment and management of resistance genes in all wheat production areas.     

Relationship between oviposition,virulence gene expression and parasitism success in <Emphasis Type="Italic">Cotesia typhae</Emphasis> nov. sp. parasitoid strains

Studying mechanisms that drive host adaptation in parasitoids is crucial for the efficient use of parasitoids in biocontrol programs. Cotesia typhae nov. sp. (Fernández-Triana) (Hymenoptera: Braconidae) is a newly described parasitoid of the Mediterranean corn borer Sesamia nonagrioides (Lefebvre) (Lepidoptera: Noctuidae). Braconidae are known for their domesticated bracovirus, which is injected with eggs in the host larva to overcome its resistance. In this context, we compared reproductive success traits of four Kenyan strains of C. typhae on a French and a Kenyan populations of its host. Differences were found between the four strains and the two most contrasted ones were studied more thoroughly on the French host population. Parasitoid offspring size was correlated with parasitism success and the expression of bracovirus virulence genes (CrV1 and Cystatin) in the host larva after parasitism. Hybrids between these two parasitoid strains showed phenotype and gene expression profiles similar to the most successful parental strain, suggesting the involvement of dominant alleles in the reproductive traits. Ovary dissections revealed that the most successful strain injected more eggs in a single host larva than the less successful one, despite an equal initial ovocyte number in ovaries. It can be expected that the amount of viral particles increase with the number of eggs injected. The ability to bypass the resistance of the allopatric host may in consequence be related to the oviposition behaviour (eggs allocation). The influence of the number of injected eggs on parasitism success and on virulence gene expression was evaluated by oviposition interruption experiments.     

Adaptation of Listeria monocytogenes in a simulated cheese medium: effects on virulence using the Galleria mellonella infection model

The aim of this study was to evaluate the effect of the acid and salt adaptation in a cheese‐based medium on the virulence potential of Listeria monocytogenes strains isolated from cheese and dairy processing environment using the Galleria mellonella model. Four L. monocytogenes strains were exposed to a cheese‐based medium in conditions of induction of an acid tolerance response and osmotolerance response (pH 5·5 and 3·5% w/v NaCl) and injected in G. mellonella insects. The survival of insects and the L. monocytogenes growth kinetics in insects were evaluated. The gene expression of hly, actA and inlA genes was determined by real‐time PCR. The adapted cells of two dairy strains showed reduced insect mortality (P < 0·05) in comparison with nonadapted cells. Listeria monocytogenes Scott A was the least virulent, whereas the cheese isolate C882 caused the highest insect mortality, and no differences (P > 0·05) was found between adapted and nonadapted cells. The gene expression results evidenced an overexpression of virulence genes in cheese‐based medium, but not in simulated insect‐induced conditions. Our results suggest that adaptation to low pH and salt in a cheese‐based medium can affect the virulence of L. monocytogenes, but this effect is strain dependent.

Significance and Impact of the Study

In this study, the impact of adaptation to low pH and salt in a cheese‐based medium on L. monocytogenes virulence was tested using the Wax Moth G. mellonella model. This model allowed the differentiation of the virulence potential between the L. monocytogenes strains. The effect of adaptation on virulence is strain dependent. The G. mellonella model revealed to be a prompt method to test food‐related factors on L. monocytogenes virulence.