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United States Department of Agriculture

Agricultural Research Service

Research Project: Enhancing Plant Resistance to Water-Deficit and Thermal Stresses in Economically Important Crops

Location: Plant Stress and Germplasm Development Research

2013 Annual Report


1a.Objectives (from AD-416):
Objective 1: Identify and characterize genetic diversity in economically important agricultural crop plants for biochemical, physiological, and metabolic processes that condition plants for tolerance to drought and heat extremes. Subobjective 1A: Identify the range of drought tolerance that exists within a diverse core reference set of entries from the National Cotton Germplasm Collection. Subobjective 1B: Contribute to the broadening of the genetic base of cotton for improved drought tolerance by developing Recombinant Inbred populations, breeding lines, and mutant populations using fast-neutron and ethyl methanesulfonate (EMS) mutagenesis. Subobjective 1C: Identify the range of heat stress tolerance in corn germplasm. Subobjective 1D: Evaluate the usefulness of a stress visualization computer software platform that can present and compare environmental and plant stress information in an interactive and manipulative environment to provide novel insights into the relationships between environmental cues and plant responses. Objective 2: Determine genetic mechanisms controlling biochemical and physiological processes that contribute to water-deficit and thermal stress avoidance and/or tolerance in agricultural crops. Subobjective 2A: Evaluate the differential onset of water stress in pre- and post-flowering sorghums via metabolite changes. Subobjective 2B: Characterize genetic and molecular mechanisms contributing to contrasting stress tolerance responses in peanuts. Subobjective 2C: Identification of major QTLs and/or genomic loci that are associated with heat tolerance/sensitive traits in maize and characterization of genetic and molecular mechanisms contributing to heat tolerant traits in maize. Subobjective 2D: Identify plant genes associated with improved abiotic stress tolerance in Arabidopsis; and functionally characterize crop ftsh11 protease homologs in maintaining chloroplast thermostability and photosynthesis at elevated temperatures. Subobjective 2E: Investigate small RNA regulation of plant stress responses and impact on transgene activity in genetically engineered plants. Objective 3: Use integrated marker-assisted breeding methods to develop stress-tolerant cotton germplasm or cultivars with high fiber quality and resistance to Fusarium oxysporium f. sp. Vasinfectum (FOV).


1b.Approach (from AD-416):
A multidisciplinary research approach will be utilized because of the complexity of the problems to be addressed. Genetic diversity will be identified for biochemical, physiological, and metabolic processes that condition plants for tolerance to drought and heat extremes. Genetic mechanisms controlling biochemical and physiological processes that contribute to water-deficit and thermal stress avoidance and/or tolerance will be determined. Marker-assisted breeding methods will be used to develop stress-tolerant cotton germplasm with high fiber quality and resistance to Fusarium oxysporium f. sp. Vasinfectum (FOV).


3.Progress Report:
A cotton environmental dataset for 2009, 2010, and 2011 was used to develop a time surface visualization system based on a GIS platform. A total of 30 time surfaces representing environmental conditions and 25 surfaces of plant parameters were created. Standardized symbology files for environmental and plant parameters have been developed to allow creation of standard surfaces for comparisons. The method has proved insightful, and current focus is on visualization of a 300 time surface dataset. Initial efforts toward implementation of the method using open-source software are underway. To determine if the enhanced pre-flowering drought sensitivity of stay-green lines may result from an inability to "sense" the soil drying until the rate of drying is too great for the stay-green lines to compensate, we have evaluated abscisic acid (ABA) and proline accumulation in response to the onset of water deficit stress of senescent and stay-green sorghums under greenhouse environments. We chose to evaluate ABA accumulation as a measure of the plants' response to the onset of water-deficit stress because abscisic acid's main function is to regulate plant water balance and osmotic stress tolerance. Because ABA leads to the expression of early response transcriptional activators, we chose to evaluate ABA responses as a surrogate for the plants' "sensing" of the onset of water-deficit stress. The results of our study showed that the post-flowering drought-tolerant (stay-green) line BTx642 did not respond to declining soil water levels as rapidly as the pre-flowering (senescent) line SC1211.


4.Accomplishments
1. Seeing patterns in large data sets. Technology allows the collection of more information than can be easily evaluated. Scientists within the Plant Stress and Germplasm Development Unit in Lubbock, Texas, have used time surface analyses to see patterns of drought stress responses in cotton. We can now evaluate several seasons of information at once, thereby allowing us to see patterns of plant responses to water deficits. These findings have generated interest in the private sector, with two companies adopting the approach for data presentation.

2. They never saw it coming. Plants need to continually sense their surroundings to protect themselves from environmental stresses. Scientists within the Plant Stress and Germplasm Development Unit in Lubbock, Texas, have evaluated sorghum lines for their ability to sense the onset of water-deficit stress. The results showed that the mechanisms responsible for sorghum post-flowering drought tolerance prevent the plant from sensing the onset of soil drying. Understanding the reason for this will help breeders develop more drought-tolerant lines by maximizing both pre- and post-flowering drought tolerance.


Last Modified: 9/23/2014
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