Objective 1. Use national collections of germplasm to identify, characterize, and exploit superior physiological traits that enhance stress tolerance and increase yield in row crops, such as cotton, maize, peanut, and sorghum, to optimize crop production strategies in water-limited management systems. • Sub-objective 1A: Evaluate a previously selected, diverse core-collection of cotton lines from the USDA germplasm collection and map developed populations for yield and fiber quality under mid- and late-season water-deficit stress and/or disease pressure. • Sub-objective 1B: Identify cotton and peanut germplasm with physiological and morphological traits important to stress tolerance and stress acclimation. • Sub-objective 1C: Characterize agro-morphological and physiological traits controlling water-deficit stress tolerance in diverse grain sorghum germplasm collections to broaden the genetic donor sources for sorghum breeding. • Sub-objective 1D: Characterize genotypic plasticity and identify genetic components of heat tolerance in maize and sorghum. • Sub-objective 1E: Isolation and genetic characterization of sorghum mutants with altered heat tolerance for major traits. Mapping and cloning the causal mutation in sorghum hs mutants and functional characterization of identified genes. • Sub-objective 1F: Physiological characterization of maize core lines for their diversity in heat stress responses. Dissection of cellular and physiological mechanisms in heat stress response in maize. (Chen) Objective 2. Develop and implement crop management systems that are most appropriate for exploiting the uniqueness or strengths of superior new varieties combined with diverse regional production practices. • Sub-objective 2A: Implementation of crop simulation models to explore the GxExM interactions in rainfed cotton and sorghum production systems. • Sub-objective 2B: Evaluation of new genetic sources of cold temperature tolerance in and development of new production schemes from planting date and in-season management to expand current season lengths and regional boundaries for sorghum production. Objective 3. Determine variability in plant environmental stress responses, and exploit the diversity by designing and evaluating genotype-specific production schemes that include assessments of environmental limitations and management interactions. • Sub-objective 3A: Advance new high-throughput, thermographic technologies for estimation of plant responses to abiotic stresses under relevant production conditions in the field. • Sub-Objective 3B: Utilize existing gene mapping technologies/tools to identify and develop new single nucleotide polymorphism markers, biomarker-trait associations, and functional genes associated with tolerance and susceptibility to abiotic and biotic stress.
Unpredictable weather patterns and insect and disease pressures continually threaten yields and quality of virtually all cropping systems. These threats, coupled with accelerating global declines in water available for irrigation and increasing reliance on production from marginal lands present substantial obstacles to achieving the goal of the ARS Grand Challenge to deliver a 20% increase in quality production at 20% lower environmental impact by 2025. The long-term goals of this research are to improve understanding of plant resilience to biotic and abiotic stresses and to develop stress-tolerant cultivars that can be used in existing and future cropping systems. The elucidation of how biological mechanisms control plant stress responses and how the environment, both natural and managed, defines and restricts crop productivity, provide the foundation for the ability to improve agricultural production in low-input systems. Significant changes in management strategies, improved selection methods, and improved germplasm will be required to meet future production demands. Genetic improvements will be derived from active, targeted selection of traits in diverse germplasm grown under relevant production scenarios. Investigations of the interactions among genetic resources, environments, and management systems provide a way to fit technologies from this research to various regional climatic zones. The proposed research is relevant to the NP 301 Action Plan, Component 1 - Crop Genetic Improvement: Problem Statement 1A, Trait discovery, analysis, and superior breeding methods and 1B, New crops, new varieties, and enhanced germplasm with superior traits; Component 2 - Plant and microbial genetic resource and information management: Problem Statement 2A, Plant and microbial genetic resource and information management; Component 3 - Crop Biological and Molecular Processes: Problem Statement 3A: Fundamental knowledge of plant biological and molecular processes; and Component 4 - Information resources and tools for crop genetics, genomics, and genetic improvement: Problem Statement 4A, Information resources and tools for crop genetics, genomics, and genetic improvement.
Objective 1. Sub-objective 1A. Field Evaluation of Cotton Germplasm for Water-deficit Stress Tolerance. Approximately 40 selected cotton breeding lines from more than 140 recombinant inbred lines derived from a cross between Phytogen 72 and NM 67 that exhibited better yields than the commercial checks in CY 2018 trials were again planted and evaluated in a replicated study using two irrigation regimes to confirm the yield advantage observed under water stress conditions and to further evaluate additional morphological and fiber quality traits. Objective 1. Sub-objectives C-E. Field Evaluation of Heat and Water-deficit Stress Tolerance for Maize and Sorghum. A phenotyping and yield trial experiment was planted in Cropping Year 2019 and is currently being evaluated for leaf and reproductive tissue response to naturally occurring heat waves events. Additionally, we have implemented a heat tent in the field to induce artificial heat waves during reproductive stage growth in maize. Leaf-level gas-exchange, chlorophyll fluorescence, continuous canopy temperature, and leaf and reproductive tissue phenotype data are being collected. Targeted sorghum mutant populations were sown as part of the phenotyping and yield trial and are currently being evaluated for heat stress response to identify mutant plants with altered heat tolerance traits in leaf and panicle tissues. The seed-producing sorghum mutants identified will be harvested at the end of the growing season and verified for specific phenotypes in greenhouse in FY20. Phenotyping data has been collected by an Unmanned Aerial System and will be analyzed with yield and biomass data at the conclusion of the growing season. Objective 2. Sub-objective 2A-C. Use of Unmanned Aerial Systems for Evaluation of Crop Establishment and Growth. A long-term rainfed planting date (8 sowing dates across 5 months) trial was sown for the 5th consecutive growing season. Additionally, and early season planting date experiment was sown to screen sorghum genotypes for cold temperature tolerance and early season seedling vigor. Crop establishment and growth data for both cotton and sorghum are currently being collected with an unmanned aerial system (drone) 3 times per week. As part of these experiments, we have developed and completed a software program to analyze the effect of gaps in plant stands that allows for tracking of individual plants from planting to harvest and provides a quantitative measure of plant growth compensation in varying plant population densities. The OZCOT cotton growth simulation modeling was modified and implemented for rainfed production systems. A user-friendly front end was developed in a Jupyter notebook framework. The results of the initial simulations are being compared to historic performance dataset for rainfed and irrigated cotton in Lubbock. Objective 3. Sub-objective 3A. Development of High-throughput Sensing and Analytics Tools for Crop Management. Research continued on the development of high-throughput sensing approaches and include the further development of a consumer-grade aerial platform for large-scale crop monitoring. Additionally, a data analytics pipeline for high-throughput data analysis is in development and a user interface for data display has been completed. Implementation of this system in CY 19 includes evaluation of germplasm in maize, sorghum, cotton, and peanut irrigation trials. Unmanned aerial systems (drones) are currently employed in a large-scale experiment on regional grower fields to evaluate cotton yield and fiber quality prior to harvest as part of an experiment addressing opportunities for modified harvest approaches. These results will be presented to growers through an end-of-season value capture framework that provides fiber yield and quality prior to and following harvest to allow maximum fiber quality on a per bale basis and provides a potential plan for custom harvesting and ginning. This work involves both USDA/ARS and Commonwealth Scientific and Industrial Research Organization for Australia (CSIRO) scientists and is currently being carried out in Texas and Australia. Research continued on the further implementation of infrared canopy temperature sensing technology, specifically through implementation of continuous field-level temperature sensing using Sentinel technology (SmartField, Inc.) and plant-level sensors (Goanna Ag. Australia). A large-scale canopy temperature-controlled irrigation experiment was started in CY 19 in collaboration with Goanna Ag, Inc., the Lugert-Altus Irrigation District, and local growers on approximately 5000 cotton acres. The implementation of a canopy temperature based irrigation management system by an Australian agricultural management company will begin in 2019 in Oklahoma and Australia. Objective 3. Sub-objective 3C. Field Screening Upland and Cotton Germplasm for Tolerance to Fusarium (FOV4) Tolerance. Continued research on identification and genotyping Upland and Pima cotton germplasm with tolerance to Fusariam wilt race 4 (FOV4), an emerging threat to cotton production in West Texas. In CY 18, more than 1000 genotypes were screened in Texas. The results of that study identified 11 Upland genotypes with tolerance to FOV4, one of which was generated by the Plant Stress and Germplasm Development Unit. Additional screening is currently underway in FOV4-infested fields in California and Texas. Improved Upland and Pima germplasm lines with FOV4 tolerance/resistance are expected to be released in late 2019 or 2020.
1. Towards the elucidation of the genetic mechanisms of heat stress tolerance. Maize is one of the most widely grown crops in the world. Like most crops, the primary limiting factors for maize production are drought and high temperature stress. While the effects of drought can be mitigated by irrigation, heat stress is often unavoidable and presents significant challenges for crop management. Researchers at CSRL and collaborators at Iowa State University identified genetic factors associated with maize heat tolerance. The result of this work identified key parts of the maize genome that are responsible for heat stress tolerance and susceptibility. Identifying these regions helps determine if they can be targeted when developing new lines for production in areas prone to heat waves and potentially marginal high temperature environments by stabilizing yields in these areas. Field trials conducted at CSRL identified maize lines with superior and hypersensitive heat stress responses based on the foliar and tassel stress response. They chose these characteristics because they are components of yield reduction when maize undergoes heat stress. Subsequently, genetic mapping studies identified specific regions controlling these responses and have the potential to be used by breeders to improve heat tolerance in maize. Two publications related to heat stress tolerance in maize and sorghum (McNellie et al. Crop Science and Chen et al. The Plant Genome) were selected for promotion in the CSA News magazine for the Agronomy, Crop Science, and Soil Science Societies.
2. Improved cotton fiber quality traits under drought stress conditions. Producing rainfed Upland cotton (Gossypium hirsutum L.) with high fiber quality has traditionally been difficult in the Texas High Plains because of extended periods of inadequate rainfall during sensitive boll developmental stages. Traditional plant breeding techniques have successfully improved the fiber quality of cotton; however, little is known about the effect of water deficit or stress environments on this fiber quality. Therefore, cotton entries with higher fiber quality were analyzed under diverse irrigation regimes. Analyses from these cotton entries showed significant improvement for fiber traits (micronaire, length, strength, uniformity, and elongation) with some entries having excellent fiber quality under diverse irrigation-regimes. Some of these entries are being considered for germplasm release and could be useful for improving the fiber quality of cotton under water limited conditions, thereby helping to ensure the long-term survival of the cotton industry on the Texas High Plains.
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