Effect of <i>Providencia rettgeri</i> (suspension at 1 and 2%) on egg to pupae recovery.

<p>Control corresponds to non infected eggs. Male represent brown pupae and Female represent white pupae. Each bar shows mean percentage ± SE.</p

Evaluation of <i>Providencia rettgeri</i> pathogenicity against laboratory Mediterranean fruit fly strain (<i>Ceratitis capitata</i>)

<div><p>The Mediterranean fruit fly (medfly) <i>Ceratitis capitata</i> (Wiedemann) (Diptera: Tephritidae), is often referred to as the most severe agricultural pest. Its biological control is mainly through the Sterile Insect Technique (SIT). Colonization, mass-rearing conditions and the irradiation process impact the competitiveness of sterile males and disrupt symbiotic associations by favoring some bacterial species and suppressing others. Levels of <i>Providencia</i> species have been shown to fluctuate considerably in the gut of the medfly laboratory strain Vienna 8 under irradiation, increasing by up to 22%. This study aimed to determine the pathogenicity of <i>Providencia rettgeri</i> isolated from the gut of laboratory Vienna 8 medfly strains by examining the effects of 1) two different treatment doses on egg-hatching and development and 2) two infection methodologies (ingestion and injection) of male and female adults according to their mating status. Treatment of eggs with <i>P</i>. <i>rettgeri</i> (2%) significantly decreased the mean egg to pupae recovery rate. Our data showed significant high mortality in flies with both injection and ingestion after 24 hours without any effect of sex. Microbial counts demonstrated that the bacteria could proliferate and replicate in adult flies. There was a significant sex-dependent effect after infection, with mortality decreasing significantly for males more than females. <i>Providencia rettgeri</i> can be considered as a potential pathogen of <i>C</i>. <i>capitata</i>. Mating protected males and females against infection by <i>P</i>. <i>rettgeri</i> by triggering an immune response leading to double the levels of <i>Cecropin</i> being secreted compared to infected virgin adults, thus reducing the virulence of the bacteria.</p></div

The relative density of cDNA amplicons of <i>Cecropin</i> gene expression (Log₂ transformed fold) in infected post-mating <i>Ceratitis capitata</i> males and females compared to virgin ones.

<p>Each bar shows mean ± SE. Different symbols correspond to a significant difference, (*) for the females (F) and (#) for the males (M), (Multivariate analysis, MANOVA).</p

Effect of mating status and infection by injection with <i>Providencia rettgeri</i> on male and female <i>Ceratitis capitata</i> mortality.

<p>Virgin infected flies are flies from experiment “Infection by injection”. Each bar shows mean percentage± SE. Different symbols correspond to a significant difference (LSD test) for the males (*) and (#) for females.</p