Cold Tolerance

1. S. Hansen1, S. Clay1, D. Clay1, D. Horvath2 and Y. Jarachi1 1South Dakota State University, Brookings, SD 2 Bioscience Research Laboratory, USDA, Fargo, ND Landscape position effects on water deficit, corn growth, and gene expression at late vegetative stage ABSTRACT RESULTS • 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. Pathways Down-Regulated in Drought Stressed corn at Summit Cold Tolerance Recovery from Wounding Nutrient Uptake Photosynthetic Capacity SUMMIT Pathways Up-Regulated in Drought Stressed corn at Summit SUMMIT 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 Plot Locations and Soil Phosphorous levels map Salt Tolerance TOESLOPE Drying Tolerance SITE-SPECIFIC MANAGEMENT TO REMEDIATE DROUGHT/LANDSCAPE EFFECTS RESULTS • 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 • 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 Antonio P. Mallarino Plants at toeslope location. Stressed plants at summit location. Pest Resistance Fungal Disease Resistance • South Dakota Corn Utilization Council • USDA-CSREES-Seed Technology Grant (2008-34556-19350) and NRI (2009-35320-05040) • SDSU Center for Excellence on Drought Tolerance Research • South Dakota 2010 Initiative