Mean relative growth rate (RGR) of <i>B. tabaci</i> females reared on standard diet (control) or high-nitrogen diet.

<p>Black bars and white bars indicate infected and noninfected females, respectively. Replicate numbers are noted within the columns. Values are means±SE. The experiment was performed three times (trial 1–3). For each paired comparison (± infection), asterisks indicate a significant difference (*, <i>p</i><0.05) based on a <i>t</i>-test.</p

Statistical parsimony network of <i>Plutella xylostella</i> mt<i>COI</i> haplotypes.

<p>The red and blue circles represents shared and unique haplotypes, respectively. Haplotype names are beside the circles. The small circles indicate the presence of missing intermediates, while the connections are based on the set of plausible solutions with a 95% of parsimony probability.</p

Mean relative growth rate (RGR) of <i>B. tabaci</i> females reared on standard diet (control) or low-nitrogen diet.

<p>Black bars and white bars indicate infected and noninfected females, respectively. Replicate numbers are noted within the columns. Values are means±SE. The experiment was performed three times (trial 1–3). For each paired comparison (± infection), asterisks indicate a significant difference (*, <i>p</i><0.05; **, <i>p</i><0.01) based on a <i>t</i>-test.</p

The Endosymbiont <i>Hamiltonella</i> Increases the Growth Rate of Its Host <i>Bemisia tabaci</i> during Periods of Nutritional Stress

<div><p>The whitefly <i>Bemisia tabaci</i> (Gennadius) (Hemiptera: Aleyrodidae) harbors several bacterial symbionts. Among the secondary (facultative) symbionts, <i>Hamiltonella</i> has high prevalence and high infection frequencies, suggesting that it may be important for the biology and ecology of its hosts. Previous reports indicated that <i>Hamiltonella</i> increases whitefly fitness and, based on the complete sequencing of its genome, may have the ability to synthesize cofactors and amino acids that are required by its host but that are not sufficiently synthesized by the host or by the primary endosymbiont, <i>Portiera</i>. Here, we assessed the effects of <i>Hamiltonella</i> infection on the growth of <i>B. tabaci</i> reared on low-, standard-, or high-nitrogen diets. When <i>B. tabaci</i> was reared on a standard-nitrogen diet, no cost or benefit was associated with <i>Hamiltonella</i> infection. But, if we reared whiteflies on low-nitrogen diets, <i>Hamiltonella</i>-infected whiteflies often grew better than uninfected whiteflies. Furthermore, nitrogen levels in field-collected whiteflies indicated that the nutritional conditions in the field were comparable to the low-nitrogen diet in our laboratory experiment. These data suggest that <i>Hamiltonella</i> may play a previously unrecognized role as a nutritional mutualist in <i>B. tabaci</i>.</p></div

UPGMA dendrogram of 23 populations of <i>Plutella xylostella</i> in China based on ISSR markers.

<p>UPGMA dendrogram of 23 populations of <i>Plutella xylostella</i> in China based on ISSR markers.</p

Insight into the Migration Routes of <i>Plutella xylostella</i> in China Using mt<i>COI</i> and ISSR Markers

<div><p>The larvae of the diamondback moth, <i>Plutella xylostella</i>, cause major economic losses to cruciferous crops, including cabbage, which is an important vegetable crop in China. In this study, we used the mitochondrial <i>COI</i> gene and 11 ISSR markers to characterize the genetic structure and seasonal migration routes of 23 <i>P</i>. <i>xylostella</i> populations in China. Both the mitochondrial and nuclear markers revealed high haplotype diversity and gene flow among the populations, although some degree of genetic isolation was evident between the populations of Hainan Island and other sampling sites. The dominant haplotypes, LX1 and LX2, differed significantly from all other haplotypes both in terms of the number of individuals with those haplotypes and their distributions. Haplotypes that were shared among populations revealed that <i>P</i>. <i>xylostella</i> migrates from the lower reaches of the Yangtze River to northern China and then to northeastern China. Our results also revealed another potential migration route for <i>P</i>. <i>xylostella</i>, i.e., from southwestern China to both northwestern and southern China.</p></div

Results of genetic diversity and neutrality tests based on <i>mtCOI</i> sequences for populations of <i>Plutella xylostella</i> in China.

<p>H, number of haplotypes; Hd, haplotype diversity; Pi, nucleotide diversity; k, average number of nucleotide differences.</p><p>*P<0.05</p><p>**P<0.01.</p><p>Results of genetic diversity and neutrality tests based on <i>mtCOI</i> sequences for populations of <i>Plutella xylostella</i> in China.</p

Locations where <i>Plutella xylostella</i> populations were sampled in China.

<p>Arrows indicate possible migration routes based on shared haplotypes. The software Adobe Photoshop CS6, Micosoft PowerPoint 2013 and Micosoft Word 2013 were used to create and modify this map.</p

Mean relative growth rate (RGR) of <i>B. tabaci</i> females reared on standard diet (control) or no-nitrogen diet.

<p>Black bars and white bars indicate infected and noninfected females, respectively. Replicate numbers are noted within the columns. Values are means±SE. The experiment was performed three times (trial 1–3). For each paired comparison (± infection), asterisks indicate a significant difference (*, <i>p</i><0.05; **, <i>p</i><0.01) based on a <i>t</i>-test.</p

Comparison of <i>mtCO1</i> haplotype frequency distributions in samples of <i>Plutella xylostella</i> from South Korean (top) and in <i>Plutella xylostella</i> populations across China (bottom).

<p>Haplotypes with frequency ≤ 2 are not shown.</p