Comparing Drought Vs Weed Stress During Late Vegetative Corn Growth Stage.

Comparing drought vs weed stress during late vegetative corn growth stage

Janet Moriles , Sharon A. Clay, David E. Clay, Stephanie Hansen , David P. Horvath, Youssef Jarachi, and Graig Reicks 

Drought and weed interference, are both major crop stress conditions that can negatively affect growth and yield.  Plant responses to drought are mainly caused by lack of adequate available water, while weed stress may be attributed to both resource independent processes and resource dependent limitations such as nutrients, water, light, and light quality changes.  Although, these two stressors have different complex mechanisms that induce plant response, they may share similarities in growth response and gene expression.  Corn was sampled at V-12 stage of plant growth in independent studies.  In the water stress study, corn grown in summit positions with low soil water was compared with corn grown in toeslope positions where soil water was adequate. Growth and gene expression were compared in weed-stressed corn with that of weed-free corn.  Gene expression was analyzed using transcriptome analysis with microarray chips and qRT-PCR in these two studies.  Corn plants under water deficit stress had 16% less leaf area, biomass, and P uptake compared with plants with adequate water available. Genes that were up-regulated in plants under water deficit stress were associated with tolerance to cold, salt, and drying.  Genes that help regulate nutrient uptake, wound recovery, pest resistance, and photosynthetic capacity, were down-regulated in drought stressed plants.  In comparison, corn grown with weeds through V12 had about 50% less leaf area and biomass compared with weed-free corn.  Down-regulated genes in weed-stressed corn involved carbon and nitrogen utilization, photosynthesis, growth and development, oxidative stress, signal transduction, responses to auxin and ethylene, and zinc transport.  Very few genes were up-regulated during late vegetative weed stress in corn and no differences were observed in genes responsive to water stress.  These data indicate weed and drought stress have limited similarities in gene expression and may indicate that if weed-stressed, adding water to ameliorate that stress may not be a successful treatment.