We have successfully developed transgenic soybean events that display a high degree of resistance towards the three primary viral agents that infect soybeans in the US: SMV, BPMV and AMV. Field releases with a subset of the virus resistant soybean events are planned for Ohio and Nebraska. Release notifications have been received from USDA/APHIS for planting in 2012. In Nebraska we will monitor for presence of the three viruses, through natural infestations, twice during the season, once in late July and second in mid September. Various agronomics data sets will be tabulated, including yield estimates and total oil and protein determination. In Ohio, plots will be artificially inoculated and impact of yield and seed quality monitored at harvest.

We are exploring the use of interfering RNAs that target critical genes in aphids as a means to perturb the life cycle of the insect. Such a strategy has been able to effectively reduce expression of critical genes in nematodes, and chewing insects. This component of the program will look at implementing such a method with aphids. Importantly, this strategy fits in to the recently drafted work plan submitted to the NCSRP entitled, “Soybean aphids research and outreach needs: A work plan has been developed for North Central Region” where it is recommended that research efforts need to address investigating promoters with high activity in phloem sieve elements, along with critical gene targets within the aphid. To this end we have assembled a binary vector that contains a synthetic micro RNA element designed to produce miRNAs that will target two genes of the aphid, C002 and a vacuolar ATPase. This vector is designated pPTN1050, and soybean transformations with this construct are completed. We have collected seed derived from 11 independent transgenic events derived from pPTN1050. Tiffany Heng-Moss (Entomology UNL) conducted aphid challenging experiments with three independent events in late January and no impact on aphid numbers were observed. This outcome was surprising given the monitoring of the miRNA production in the transgenic events revealed the accumulation of the miRNAs was low, and secondly the two miRNAs were not being processed into individual molecules. We have now re-designed the genetic elements with a strategy we believe will address these two bottlenecks, accumulation and proper processing of the molecules. We expect to initiate soybean transformations with the new genetic designs by mid June 2012.

A second, complementary approach to the miRNA will target these same to aphid genes, but utilize a hair-pin construct to produce interfering RNAs in planta, in an analogous fashion as used to derived the virus resistance described above. A plasmid designated pCCW has been assembled that carries a double “hair-pin” with sequences from the target genes of the aphid. Soybean transformations were initiated with this construct at the end of Sept 2011. Primary transgenic soybean events have been established in the greenhouse and we will begin molecular characterization of these within the next month, and evaluate aphid resistance in progeny, which we plan to initiate in August 2012.