Stonebrood and chalkbrood in <i>Apis mellifera</i> causing fungi:<i> in vitro </i>sensitivity to some essential oils

<p>Aim of the present study was to evaluate the <i>in vitro</i> antimycotic activity of 17 chemically defined essential oils (EOs) both alone and as a mixture, against agents responsible for stonebrood caused by <i>Aspergillus flavus</i>, and chalkbrood caused by <i>Ascosphaera apis</i> in European honeybees. <i>Cinnamomum zeylanicum</i> yielded the lowest MIC value against <i>A. flavus,</i> but was not effective against <i>A. apis,</i> while <i>Litsea cubeba</i> and <i>Pelargonium graveolens</i> appeared to be effective against all checked fungi. <i>Aspergillus niger</i> showed the lower sensitivity. Two mixtures composed by <i>L. cubeba</i>, <i>C. zeylanicum</i> and <i>Cymbopogon flexuosus</i> (M1) and by <i>L. cubeba</i>, <i>C. zeylanicum</i>, <i>P. graveolens</i> and <i>C. flexuosus</i> (M2), respectively, were tested, both resulting effective. The components of M1 showed a synergistic effect. The use of mixtures allowed to decrease the total amount of EOs. The use of these products could be of interest for an alternative natural approach in honeybee disease management.</p

Venn diagram illustrating the significantly affected genes (A), isoforms (B) and TSS (C) between infections at days 5, 10 and 15 P.I.

<p>Venn diagram illustrating the significantly affected genes (A), isoforms (B) and TSS (C) between infections at days 5, 10 and 15 P.I.</p

Principal component analysis of RNA-seq data.

<p>Gene expression changes were investigated at days 5, 10 and 15 P.I. in honeybees infected (INF) with <i>N</i>. <i>ceranae</i> or no treatment (CR). The PCA was performed using normalized RNA-Seq data of 675 genes differentially expressed in at least one pairwise comparison: control vs infection at day 5 10 P.I or 15 P.I.Clear differences were seen between samples collected at days 5, 10 and 15 suggesting that ageing of the bees has a larger effect on the pattern of gene expression pattern than infection status.</p

Expression profiles of the genes involved in the 'metabolic pathways'.

<p>The X axis shows the time points following infection (days 5, 10 and 15 P.I). On the Y axis, genes expression fold changes.</p