1. Cold Tolerance Salt Tolerance Drying Tolerance Nutrient Uptake Recovery from Wounding Photosynthetic Capacity Pest Resistance Fungal Disease Resistance Antonio P. Mallarino Landscape position effects on water deficit, corn growth, and gene expression at late vegetative stage S. Hansen 1, S. Clay 1, D. Clay 1, D. Horvath 2 and Y. Jarachi 1 1 South Dakota State University, Brookings, SD 2 Bioscience Research Laboratory, USDA, Fargo, ND  Soil P was 225% greater at the summit (8.5 ug/g vs 4 ug/g, p=0.00), but summit plants contained only 10% more P (120 mg/plant vs 100 mg/plant, p=0.05) than toeslope plants  Plants at the summit had 29% lower biomass than toeslope plants (p=0.01)  Corn at the summit had 15% less leaf area compared with toeslope position (p=0.01).  800+ gene expressions affected by drought  Cascade of multiple events from one or two main effects of drought  Some traits were improved/enhanced, but only at the cost of several other traits and abilities being diminished  In general, the plants ability to withstand and recover from pests was severely decreased SITE-SPECIFIC MANAGEMENT TO REMEDIATE DROUGHT/LANDSCAPE EFFECTS  Water stress on corn growth and gene expression was examined in a field setting at the V12 stage at summit (low soil water) and toeslope (adequate soil water) field positions.  Gene expression in the summit showed  Up-regulated genes involved in cold, salt, and drying tolerance.  Down-regulated genes involved in nutrient uptake, wound recovery, pest and fungal disease resistance, photosynthetic capacity, and circadian rhythm which negatively impacts flowering, growth, and nutrient uptake.  Water-stress not only affects plant top-growth but also the ability to uptake nutrients and withstand and recover from pest attacks. ABSTRACT MATERIALS AND METHODS Field Experiment  A 97-d corn hybrid planted in May 2008 at a Moody County, SD field site  At V12: at 10 summit and 5 toeslope locations:  4 newly emerged leaf tips sampled for RNA extraction  Two corn plants were harvested for  leaf area,  biomass,  nutrient content.  Soil samples from the 0-15 and 15-60 cm depths analyzed for  water,  P content, and  N content  RNA microarrays and verification with quantitative RealTime-PCR RESULTS Pathways Down-Regulated in Drought Stressed corn at Summit Pathways Up-Regulated in Drought Stressed corn at Summit  Reduce inputs and potentially increase yield and/or grain quality  In water-challenged areas:  Decrease plant population densities  Use more efficient corn varieties  Increase N Rates (nutrient uptake remediation)  Optimize Fungicide Application (fungal resistance remediation)  Lower pest thresholds (pest resistance remediation)  For example: corn leaf aphid:  Non-drought = 80% infestation  Drought = 40% infestation RESULTS  South Dakota 2010 Initiative  SDSU Center for Excellence on Drought Tolerance Research  USDA-CSREES-Seed Technology Grant (2008- 34556-19350) and NRI (2009-35320-05040)  South Dakota Corn Utilization Council Plot Locations and Soil Phosphorous levels map SUMMIT TOESLOPE Plants at toeslope location. Stressed plants at summit location.