Cold Tolerance

1
Landscape position effects on water deficit, corn
growth, and gene expression at late vegetative
stage
S.
Hansen1, S. Clay1, D. Clay1, D. Horvath2 and Y.
Jarachi1 1South Dakota State University,
Brookings, SD 2 Bioscience Research Laboratory,
USDA, Fargo, ND
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
Pathways Up-Regulated in Drought Stressed corn at
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

• Cold Tolerance

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, p0.00), but summit plants contained
  only 10 more P (120 mg/plant vs 100 mg/plant,
  p0.05) than toeslope plants
• Plants at the summit had 29 lower biomass than
  toeslope plants (p0.01)
• Corn at the summit had 15 less leaf area
  compared with toeslope position (p0.01).
• 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

Plants at toeslope location.
Stressed plants at summit location.