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United States Department of Agriculture

Agricultural Research Service

Research Project: Identification and Analysis of Host Resistence and Hessian Fly Response in Wheat

Location: Crop Production and Pest Control Research

Project Number: 3602-22000-018-03
Project Type: Specific Cooperative Agreement

Start Date: Sep 10, 2013
End Date: Jul 31, 2017

Objective:
Thoroughly investigate the fitness cost of vH5 to Hessian fly in the northwestern US. Cooperators expertise in landscape ecology will complement laboratory based research on the evolution of virulence by taking into account the geographic topography and characteristics unique to the northwest. It allows us to determine if environmental variables are at play or if it is truly genetic differences (i.e. strong fitness costs) in the Hessian fly found in the northwest that prevents it from overcoming vH5, a gene that was deployed in the southeast and is ineffective against Hessian fly now.

Approach:
We will assess fitness costs by comparing basic reproduction number life history traits (hatch to first larval instar, number of eggs laid, and growth rate). We will collect Hessian fly from field and greenhouse collections from both Idaho and Georgia and compare these two populations over the course of 8 generations. In each generation, 30 single female pots will be assessed on the above mentioned life history traits. Larvae will be observed 5 days after infestation when they should be molting to the second instar. An individual plant will be examined and marked for living or dead larvae. Only one plant at this time will be analyzed as it will require destructive sampling. The rest of the plants will be able to provide information about survival to the adult stage and the size of adults. Analysis of the resulting data will be done by individual collections of Idaho v Georgia flies, and if there is no significant population differentiation seen (determined by significant F statistics), all collections from Idaho will be compiled and compared to all collections of Georgia flies. Some measures such as number of eggs per plant that hatched/by total eggs per plant will be expressed as percentages. Likewise, larval survival will be calculated as the number of larvae per plant found divided by the number of eggs per plant that hatched. Survival from egg to adult will be calculated as total number of adults per plant divided by total eggs per plant. Insect genotype and gender will be taken into account using a generalized linear mixed model with a binomial distribution modeling the response variable, a logistic link function, and block and plant as random factors. In addition, landscape genetics approaches will be utilized to allow previously unobtainable variables to be compared against the data collected in the laboratory. Wheat planted as hay percentages, wild grass coverage in the area, topography and other potential geographic variables can be used in order to compare populations between the two demographic areas to allow us to ascertain the fitness cost of vH5 in Hessian fly. Analysis of the landscape genetic variables will be done employing a variety of methods including ArcGIS to determine distances between coordinates, and Mantel tests to compare the data between the collections as well as the landscape variables.

Last Modified: 4/24/2014
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