2009 Annual Report
1a.Objectives (from AD-416)
The objective of this research is to increase understanding of the molecular basis of host resistance and insect virulence in the wheat/Hessian fly system. The long-term goal is to develop strategies for durable resistance to this important insect pest.
1b.Approach (from AD-416)
The molecular basis of host resistance will be approached by cloning and characterizing a wheat resistance gene for Hessian fly known as Hdic from Triticum turgidum subsp. dicoccum. This resistance gene resides in a region of wheat chromosome 1A that contains at least 14 other resistance genes for Hessian fly. Candidate genes will be identified by fine mapping and sequencing of BAC contigs. Candidate genes will be tested initially by gene silencing using RNA interference. A cosmid library from the donor of Hdic will be constructed to isolate the resistance allele. Expression vectors will be constructed for the candidate gene and tested for ability to confer resistance to Hessian fly.
The molecular basis of Hessian fly virulence/avirulence will be approached by determining the functions of secreted salivary gland proteins (SSGP) of Hessian fly in virulence or avirulence to wheat. Differential gene expression of SSGPs will be tested in different biotypes of Hessian fly using a custom-designed microarray. Candidate genes for virulence or avirulence effectors will be identified. Candidate genes will be tested by gene silencing using RNA interference.
The objective of this research is to increase understanding of the molecular basis of host resistance and insect virulence in the wheat/Hessian fly system. The long-term goal is to develop strategies for durable resistance to this important insect pest. The most significant accomplishment of the past year was the finding that reactive oxygen species (ROS) are part of plant defense against Hessian fly larval attack. This finding is important because in the literature, a previous report indicated that NADPH-dependent oxidases are not involved in wheat defense against Hessian fly larval attack. Since NADPH-dependent oxidases are key enzymes responsible for generation of ROS in many plant-pathogen systems, the lack of involvement of NADPH-oxidase in the wheat-Hessian fly interaction suggested that ROS are not part of wheat defense against Hessian fly. We discovered a high level of ROS, particularly hydrogen peroxide, accumulated in plants during resistant interactions, but no change in ROS in plants during susceptible interactions. This information increases our understanding of resistance and susceptibility in this insect-plant system.
Progress on this agreement is monitored by regularly discussing program goals, approaches, and results (teleconference, email) and by reviewing annual accomplishments reports.