Progress 10/01/12 to 09/30/13
Outputs
Progress Report Objectives (from AD-416): Although aphid endosymbionts are known to confer resistance to attack by some parasitoid species, very little is known about the impacts such endosymbionts have on biological control of pest aphids. We will determine whether the aphid endosymbiont HAMITONELLA DEFENSA affects parasitism by APHELINUS species being considered for introduction against pest aphids. Approach (from AD-416): We will test whether parasitism of APHIS CRACCIVORA by APHELINUS species that are candidates for introduction against soybean aphid is affected by the presences of HAMITONELLA DEFENSA. In several experiments on the effect of HAMITONELLA DEFENSA, a bacterium living in aphids, on resistance of the cowpea aphid, APHIS CRACCIVORA, to parasitism by APHELINUS GLYCINIS, APHELINUS ATRIPLICIS and APHELINUS CERTUS, neither parasitism nor adult body size of progeny were affected by the presence of H. DEFENSA. Thus although H. DEFENSA has been shown to confer resistance to parasitism by braconid wasps that attack aphids, it does not confer resistance to aphelinid wasps that attack aphids. We found 11 strains of bacteria in 6 genera in 44 populations of the aphid cowpea aphid, APHIS CRACCIVORA. However, prevalences of bacteria were lower than in other well-studied aphids. ARSENOPHONUS was prevalent in cowpea aphid on locust but rare or absent on other plants; HAMILTONELLA was prevalent in cowpea aphid on alfalfa but rare or absent on other plants. HAMITONELLA provides protection against some parasitic wasps, but ARSENOPHONUS does not, so aphids on different host plants may have different levels of parasitism.
Impacts
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Progress 10/01/11 to 09/30/12
Outputs
Progress Report Objectives (from AD-416): Although aphid endosymbionts are known to confer resistance to attack by some parasitoid species, very little is known about the impacts such endosymbionts have on biological control of pest aphids. We will determine whether the aphid endosymbiont HAMITONELLA DEFENSA affects parasitism by APHELINUS species being considered for introduction against pest aphids. Approach (from AD-416): We will test whether parasitism of APHIS CRACCIVORA by APHELINUS species that are candidates for introduction against soybean aphid is affected by the presences of HAMITONELLA DEFENSA. A previous experiment on the effect of a endosymbiotic bacteria of aphids (HAMITONELLA DEFENSA) on resistance to parasitism by APHELINUS GLYCINIS, a candidate for introduction against soybean aphid, showed that although parasitism was not significantly affected, adult body size of parasitoid progeny was smaller in HAMITONELLA-infected aphids than in HAMITONELLA- free APHIS CRACCIVORA of the same genotype. We carried out an experiment to confirm this result using both APHIS CRACCIVORA and ACYTHROSIPHUM PISUM. We are also testing whether the effects differ for a parasitoid species with a broader host range, APHELINUS CERTUS, which was accidentally, introduce into the United States and is now parasitizing soybean aphid.
Impacts
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Progress 10/01/10 to 09/30/11
Outputs
Progress Report Objectives (from AD-416) Although aphid endosymbionts are known to confer resistance to attack by some parasitoid species, very little is known about the impacts such endosymbionts have on biological control of pest aphids. We will determine whether the aphid endosymbiont HAMITONELLA DEFENSA affects parasitism by APHELINUS species being considered for introduction against pest aphids. Approach (from AD-416) We will test whether parasitism of APHIS CRACCIVORA by APHELINUS species that are candidates for introduction against soybean aphid is affected by the presences of HAMITONELLA DEFENSA. In experiments with APHIS CRACCIVORA, we found that the presence of a symbiotic bacteria of aphids (HAMITONELLA DEFENSA) known to affect parasitism by aphidiine parasitoids of aphids had no effect on resistance to parasitism by two species of APHELINUS, one with a narrow host range and another with a broad host range. APHELINUS has large, heavily chorionated eggs that absorb nothing from their hosts during development, whereas aphidiine parasitoids heavy small porous eggs that absorb nutrients from their hosts, and thus allow uptake of the toxin produced by the bacteriophage in HAMILTONELLA. This may explain the difference in impact of HAMITONELLA on APHELINUS versus aphidiine parasitism.
Impacts
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Progress 10/01/09 to 09/30/10
Outputs
Progress Report Objectives (from AD-416) Although aphid endosymbionts are known to confer resistance to attack by some parasitoid species, very little is known about the impacts such endosymbionts have on biological control of pest aphids. We will determine whether the aphid endosymbiont HAMITONELLA DEFENSA affects parasitism by APHELINUS species being considered for introduction against pest aphids. Approach (from AD-416) We will test whether parasitism of APHIS CRACCIVORA by APHELINUS species that are candidates for introduction against soybean aphid is affected by the presences of HAMITONELLA DEFENSA. The heritable bacterial symbiont, HAMILTONELLA DEFENSA, protects the pea aphid from attack by parasitoid wasps. Preliminary data suggest that H. DEFENSA also defends cowpea aphid, APHIS CRACCIVORA, against parasitoids. However, the bacterium may not protect the aphids equally well across parasitoid taxa because some parasitoids have eggs that absorb nutrients during development (hydropic, e.g. braconids) and others have eggs that do not (anhydropic, e.g., aphelinids). We are testing the hypothesis that H. DEFENSA-infected A. CRACCIVORA resist parasitism by APHELINUS species. We will compare results from this aphelinid which has anhydropic eggs with those from braconid species with hydropic eggs. Monitoring was achieved through frequent telephone calls and emails.
Impacts
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