2012 Annual Report
Objective 2: Microarray technology and 454FLX sequencing will reveal gene expression in the larval Hessian fly during compatible and incompatible interactions with wheat. The morphology of midgut and salivary gland tissues will be examined by transmission electron microscopy. Comparative transcriptomics will identify Hessian fly genes involved in parasitism of wheat. The role of Hessian fly genes in host susceptibility or resistance will be assessed through RNAi knockdown.
Objective 3: Microsatellite markers will be used to assess heterogeneity and gene flow in Hessian fly populations. Changes in allelic variation will assist in assessing the risks to deployed resistance. Differentiation at different geographic scales will be assessed by Fst and Rst values. Estimation of effective population size (Ne) will be used to measure the strength of genetic drift in populations.
Objective 2 – Using the Hessian fly genome sequence we have annotated genes and pathways that are essential to survival of the insect and its interactions with wheat. Genes annotated include those in the RNA interference and microRNA pathways, metabolic pathways, synthesis of non-essential amino acids, detoxification/antioxidant defense, and digestion. An assay that allows toxic proteins to be evaluated for transgenic resistance in wheat to Hessian fly was developed and published. Using this assay we have discovered a toxic recombinant protein that has potential for resistance in wheat. Currently, wheat is being transformed with the transgene encoding the protein. Future studies will evaluate other toxic proteins to include Bacillus thuringiensis endotoxins (BT toxins).
Objective 3 – The microsatellites that have been chosen for use in population studies have been characterized and mapped to the polytene chromosomes. These microsatellites have been used to analyze population structure globally by assessing gene flow between populations. A macrogeographic study of Hessian fly populations in the southeastern United States has been completed and published. In addition, a microgeographic study with populations in Alabama is currently underway to gain better understanding of gene flow within small geographic distances.
Shukle, R.H., Subramanyam, S., Williams, C.E. 2011. Effects of antinutrient proteins on Hessian fly (Diptera: Cecidomyiidae) larvae. Journal of Insect Physiology. 58:41-48.
Williams, C.E., Shukle, J.T., Nemacheck, J.A., Subramanyam, S., Saltzmann, K., Shukle, R.H. 2011. Induced epidermal permeability modulates resistance and susceptibility of wheat seedlings to herbivory by Hessian fly larvae. Journal of Experimental Botany. 63:4521-4531.
Mittapalli, O., Rivera-Vega, L., Bhandary, B., Bautista, M.A., Mamidala, P., Michel, A.P., Shukle, R.H., Mian, R.M. 2011. Cloning and characterization of mariner-like elements in the soybean aphid, Aphis glycines Matsumura. Bulletin of Entomological Research. 102(6):697-704.
Baluch, S.D., Ohm, H.W., Shukle, J.T., Williams, C.E. 2012. Obviation of wheat resistance to the Hessian fly through systemic induced susceptibility. Journal of Economic Entomology. 105(2):642-650.