Progress 12/01/09 to 11/30/12
Outputs
OUTPUTS: The project defined the physiological benefit and genetic regulation of increased leaf epicuticular wax composition played during drought stress in wheat. The study focused on two genetic mapping populations, the 1st a recombinant inbred line population and a 2nd wheat association mapping population. We have completed three years of yield and leaf and glume wax phenotypic studies at 3 locations in Texas and 1 in Sonora, Mexico, 2 locations in Bangladesh and 1 in India. Each site had duplicate trials of the two mapping populations. One was control and well watered, the 2nd was drought with no irrigation following flower initiation, Feekes 5. Phenotypic yield components, end-use quality and physiological data were collected. The later included canopy temperature, photosynthesis, and leaf wax content and chemical composition. This data has been used to associate high epicuticular wax to cooler plant canopies, increased water-use efficiency, and increased yield and quality stability during drought and heat stress. Drought tolerant wheat lines have been developed that were selected using high epicuticular wax as a phenotypic screen. The project included extensive collaboration and dissemination of methods on wax content and composition analysis. These included Texas A&M University faculty and extensive international collaboration with Dr. Matthew Reynolds at the International Maize and Wheat Improvement Center (CIMMYT) in Mexico, Dr. Marta Da Silva, CIMMYT, Turkey, Dr. Dr. V.K Mishra at Banaras Hindu University in Varanasi India, and Dr. Naresh Barma at Bangladesh Agricultural Research Institute in Bangladesh. The projected has produced 10 accepted publications, 1 book chapter, and 10 additional soon to be submitted publications. Our results were extensively conveyed to consumers, wheat producers, academic and industry audiences. These include: Press articles to US-CIES-Fulbright; Texas newspapers; Online crop news sources; Presentations to the Texas Wheat Producers Board; Texas wheat producers at farm field days; Three presentation in India and Bangladesh as a US Fulbright Fellow; Presentations to scientists at CIMMYT and at the International Center for Agriculture Research in the Dry Areas (ICARDA) in Amman, Jordan; Invited presentations to the Society for Experimental Biology, Glasgow Scotland; 15 invited graduate student talks to Crop Science Society of America; 2 to the National Association of Plant Breeders; and 5 to the American Society of Plant Biology. The project has supported the training of 14 graduate students (11 Ph.D. and 4 M.S.). These students were supported on $380,000 in additional competitive graduate fellowships from Monsanto, the State of Texas, and the Government of Egypt. The project has graduated 2 M.S. and 3 Ph.D. students and will graduate an additional 4 Ph.D. students by the end of 2013. One student is an Assistant Professor of Wheat Breeding at the University of Arkansas (Dr. Esten Mason), one a wheat breeder for CIMMYT (Dr. Suchismita Mondal), and one a corn breeder for Monsanto (Dr. Francis Beecher, recipient of the National Consortium of Commercial Plant Breeders Graduate Student Award). PARTICIPANTS: Project Directors: Dirk B. Hays, Associate Professor, Chair Molecular and Environmental Plant Sciences, Texas A&M University. Directed the implementation, experimental design, data acquisition, and data analysis, and reporting of data at national meetings and in peer-reviewed publications. He managed 12 graduate students who worked on the project, and facilitated collaboration with international partners. Amir Ibrahim, Professor, Department of Soil and Crop Sciences, Texas A&M University, facilitated experimental design, data acquisition, and data analysis. Collaborators: Drs. Matthew Reynolds and Marta Da Silva, Wheat Physiologist, CIMMYT, Mexico. Directed planting and physiological and yield data acquisition and analysis of the wheat association mapping panel used in this study at Cuidad Obregon, Mexico. Drs V.K. Mishra, Professor Wheat Breeder, Banaris Hindu University, India, and N.C. Barma, Wheat Breeder, Bangladesh Agriculture University, Directed planting and physiological and yield data acquisition and analysis of the wheat association mapping panel used in this study at Varanasi, India and Gazipur and Dinajpur, Bangladesh, respectively. Graduate Students: Dr. Richard E. Mason, Ph.D. Molecular and Environmental Plant Sciences, Texas A&M University (presently, Assist. Professor, Department of Crop Sciences, University of Arkansas), and Dr. Suchismita Mondal, Ph.D. Plant Breeding Department of Soil and Crop Sciences, Texas A&M University (presently, CIMMYT, Mexico), facilitated experimental design, data acquisition, and data analysis, and genetic mapping of one recombinant inbred line used in this study. Dr. Francis Beecher, Ph.D. Plant Breeding Soil and Crop Sciences, Texas A&M University (presently, Corn Breeder, Monsanto, Iowa City, Iowa), and Mr. Chris Chick, current Ph.D. student, Molecular and Environmental Plant Sciences, Texas A&M University, facilitated experimental design, data acquisition, and data analysis of wax content in association to drought tolerance in wheat, and genetic mapping of wheat association mapping panel used in this study. Mr. Suheb Mohammed, Mr. Trevis Huggins, Mrs. Padma Sengadon, and Mrs. Ashima Poudel, current Ph.D. students, Plant Breeding, Soil and Crop Sciences, Texas A&M University, facilitated experimental design, data acquisition, and data analysis of wax content in association to drought tolerance in wheat, and genetic mapping of the recombinant inbred lines used in this study. TARGET AUDIENCES: The primary focus of the project was to optimize wheat leaf and glume epicuticular wax content in new wheat, sorghum and corn cutlivars and hybrids for improved heat and drought tolerance, ideal yield, and increased water use efficiency during drought and high temperature stress. As such, the outcome of this research is to increase yields in these crops during stress while reducing irrigation and increasing resilience to global climate change. The intended audiences that were served by this project include U.S. Southern Great Plains and Indo-Gangetic Plains wheat, sorghum and corn producers in the US, Mexico, and India and Bangladesh. They also include corporate seed producers, and millers and bakers who rely on wheat and prefer wheat with ideal end-use quality, a straight which is improved by increased heat and drought tolerance. In addition, the research helps the consumer of wheat products, and communities that compete for limited water resources. Lastly, this research, which enhances wheat yields during drought and heat stress, also stabilizes national and international food security and global stability by ensuring the world has an adequate supply of wheat. Wheat is globally the most important crop and second most important food crop in the developing world. Wheat prices have also increased 2-3 fold during this period. This latter consequence has influenced the social unrest termed "Arab Spring" in North Africa and the Middle East. As Lagi et al., (2011, http://arxiv.org/abs/1108.2455) demonstrated, there is a direct correlation between peaks in wheat prices and the food price index [which has tripled since 2002 (FAO, 2013)] and the start of the "Arab Spring" events. It should be noted that the percentage of annual income spent on food in much of the Arab Spring countries averages near 40%, versus 7% in the U.S. (FAO, 2013). As such, higher wheat yields that will be required in the future during increasing incidences of drought and high temperature stress due to global climate change (GCC) not only have significance for economic and food supply stability, but also for global social stability. PROJECT MODIFICATIONS: This project primarily focused on the role that increased leaf wax played in increasing wheat adaptation to drought and high temperature stress. One key modification that was learned as part of this project, that ear, flower or glume epicuticular wax is independently inherited, and is equally important in maintaining wheat yields by cooling spike temperatures during hot dry conditions.
Impacts
As part of this project, we compared the diverse genotypes discussed above for wax content and spectral reflectance, in relation to yield maintenance in response to heat stress in controlled greenhouses. Evident from these comparisons is that the drought and heat tolerant wheat genotypes, have high levels of cuticular wax, in some instances in a double layer that extends several μm above the cell wall plane as an amorphous cuticular layer, cuticle proper, and crystalline epicuticular layer. Drought tolerant genotypes have statistically higher (20 to 30%) pre heat stress spectral reflectance in the near-infrared, infrared and ultraviolet wavelengths compared to the heat susceptible genotypes. The blue and ultraviolet regions increase the photosynthetic excitation, while the near infrared and infrared are nonphotosynthetic wavelengths that are absorbed water in the plants cells as heat. This heat must be dissipated as transpiration through stomates as water loss. In contrast, the heat susceptible wax layer appears only as a thin crystalline epicuticular wax layer. The spectral reflectance in these lines is lower in the photosynthetic, near-infrared and infrared wavelengths. We showed that high wax content correlates with higher grain yields, yield stability, and lower canopy temperatures and transpiration in response to drought stress. We have also defined the genetic regulation of high epicuticular wax using quantitative trait loci (QTL) mapping in three unique mapping populations. We have defined 3 QTL that regulate wax content on chromosome 1B, 3B, and 5A. The loci regulatie leaf wax and grain yield and decrease spike and leaf temperatures. These same QTL also regulate quality stability. Our study showed a strong relationship between increasing epicuticular wax and cooler plant canopies and lower transpirational cooling or water demand. We have also shown that 1 QTL, increase leaf wax content by 100%, decreases leaf and spike temperatures by 1 to 2 degrees celsius, and increases yield during drought stress by 25% under field conditions. In collaboration with CIMMYT, we also tested two unique sets of near-isogenic lines for two characterized genes known to differ in drought tolerance and resistance to three chronic pathogens of wheat. The two sets of isolines consisted of the parent resistant line and multiple single mutation knockouts of the single gene. Using mass spectrometry, we demonstrated that both genes function to alter epicuticular wax composition by lowering chain length wax alkane units. However, both genes do not influence wax quantity. We have also shown, that the two genes influences the deposition of wax crystals on the surface of the leaf wax layer in a manner that occludes the stomatal opening, yet does not alter stomatal conductance or transpiration. Our results have demonstrated that both wax content and composition are important for ideal adaptation to drought, and heat stress and contribute to disease resistance. In collaboration with our program, the Texas A&M and CIMMYT wheat breeding programs now focuses on optimizing leaf wax content for drought, heat and disease resistance.
Publications
- Cooper, J., A.M.H. Ibrahim, J. Rudd, D. Hays, J. Baker, and S. Malla. 2012. Increasing Hard Winter Wheat Yield Potential via Synthetic Wheat: II. Heritability and Combining Ability of Yield and its Components. Crop Science (accepted).
- Tom O. Jondiko, Novie J. Alviola, Dirk. B. Hays, Amir Ibrahim, Michael Tilley, and Joseph M. Awika, 2012 ,Effect of high molecular weight glutenin subunit allelic composition on wheat flour tortilla quality. Cereal Chemistry 89:155-161.
- Beecher, F., Mason, R.E., Mondal, S., Hays, D.B. 2012. Identification and validation of QTL associated with maintenance of bread making quality under heat stress in wheat (Triticum aestivum L.), Euphytica 188: 361-368.
- Mason R.E., Mondal S., Beecher F., Ibrahim A., Hays D.B. 2010. Quantitative loci regulating yield maintenance under reproductive stage heat stress in wheat. Euphytica 174: 423-436.
- Ali M., Ibrahim A.H.,Hays, D.B., Ristic Z. Fu J. 2010. Response of Wild Tetraploid Wheat (Triticum turgidum L.) to Heat Stress. J. Crop Improv. 24:228-243.
- Reynolds M.P., Hays D.B., Chapman S. 2010. Breeding for adaptation to heat and drought stress, In: Climate change and crop production, Reynolds M.P. (Ed.), CABI Inc.
- Hays D.B. 2012. Linking genetic loci in wheat that regulate the distinct wax cuticle layers and its variable composition to Improved Drought Tolerance, USDA-AFRI, Grantees Meeting.
- Hays, D.B. 2012. Ground Penetrating Radar and Terrestrial Laser Scanning Tools in wheat phenotyping. Monsanto Science Fellows Symposium, Chesterfield, MO.
- Hays D.B. Mishra V.K. 2012. Sustainable Agroecosystesm: harmony with nature: Symposium on Sustainable Agriculture and Human Health, Udder Pradesh Normal University, Allahabad, India.
- Acuna-Galindo MA, Subramanian NK, Hays DB, Mason, RE. 2013.Meta-analysis of wheat QTL regions associated with adaptation to drought and heat stress. Theoretical and Applied Genetics (submitted).
- Meeks, M.; Murray, S.; Hague, S.; Hays, D. 2013. Measuring Maize Seedling Drought Response in Search of Tolerant Germplasm. Agronomy 3: 135-147.
- Mondal, S, Mason RE, Ibrahim A, Hays DB. 2012. Defining the Molecular and Physiological role of Leaf Cuticular Waxes in Reproductive Stage Heat Tolerance, Journal of Agronomy and Crop Science, (submitted).
- Ali, M., A.M.H. Ibrahim, J. Rudd, D. Hays, S. Malla, and Z. Ristic. 2012. Family-based QTL mapping of heat stress tolerance in wild tetraploid wheat (Triticum turgidum L.)s. Euphytica 10.1007/s10681-012-0824-8.
- Cooper, J., A.M.H. Ibrahim, J. Rudd, D. Hays, J. Baker, and S. Malla. 2012. Increasing Hard Winter Wheat Yield Potential via Synthetic Wheat: I. Path-coefficient Analysis of Yield and its Components. Crop Science 52:2014-2022.
- Hays D.B. Barma NCD. 2012. Sustainable Agroecosystesm During Climate Change, Symposium on Sustainable Agriculture and Human Health, USA-AID, Dhaka, Bangladesh.
- Hays D.B., Mason R.E., Mondal S., Beecher F.. 2011. Genetic regulation of leaf epicuticular wax and its overlap with drought, heat and disease resistance. Society of Experimental Biology, Glasgow, Scotland.
- Thompson, S.M. Hays, D.B. 2012. Use of ground-penetrating radar in root phenotyping., Texas A&M University, Texas AgriLife Research Experiment Station, Uvalde, Texas.
- Sengadon, P., Hays, D.B. 2012. Mapping drought tolerance genes in wheat, Wheat and Oat Field Day, Texas A&M University, Texas AgriLife Research Experiment Station, Uvalde, Texas.
- Huggins T, Hays D.N. 2012. Epicuticular Wax: Its Deposition During the Reproductive Stages of Wheat in Response to Heat Stress, ASA,CSA,SSSA, Cincinnati, Ohio 97-24.
- Thompson S.M., Delgado, A., Franks, A.M., Washington-Allen, R.A., Duncan, R.W., Ibrahim A., Hays D.B. 2012. Estimating Forage Wheat Biomass From 3-D Vegetation Parameters Collected Using a Terrestrial Laser Scanner. ASA,CSA,SSSA, Cincinnati, Ohio 97-26.
- Beecher F.W. Chick, C., Jeanotte R., Domin, M. Ibrahim A., Hays, D.B. 2012. Investigation of Compositional Differences in Epicuticular Wax Between Wheat Lines, ASA,CSA,SSSA, Cincinnati, Ohio 97-26, 360-368.
- Thompson S, Brademan W, Barber B, Delgado A, Austin M, Hays D, Washington-Allen R. 2011. Estimating changes in above-and below-ground 3-D vegetation structure in a model savanna using ground-penetrating radar and terrestrial laser scanning, ASPB, St. Paul, MN.
- Beecher F, Chick C, Mohammed S, Poudel A, Huggins T, Ibrahim A, Hays, 2010. Investigation of the Role of Epicuticular Wax On Heat and Drought Tolerance in Wheat (Triticum aestivum). ASA-CSSA-SSSA, Long Beach, CA.
- Jampala B, Hays D, Rooney W, Peterson G, Awika J. 2010. Fine Mapping the High Endosperm Digestibility Trait Using near-Isogenic Lines in Sorghum. ASA-CSSA-SSSA, Long Beach, CA.
- Pacheco A, Mondal S, Singh R. Hays D. 2010. QTL Map Associated with Wax Content and Disease Resistance in Wheat. ASA-CSSA-SSA, Long Beach, CA.
- Mondal S, Hays D. 2010. Molecular Mapping and Characterization of Flag Leaf Wax in Wheat (Triticum aestivum L.). ASA-CSSA-SSSA, Long Beach, CA.
- Beecher F., Mason R.E., Mondal S., Hays D.B. 2010. Mapping QTLs that regulate end-use quality stability during reproductive stage heat stress in wheat. Hard Winter Wheat Workshop, Lincoln, Nebraska.
- Mondal S., Hays D.B. 2010. Leaf Epicuticular Wax Improves Heat Tolerance in Wheat. Hard Winter Wheat Workshop, Lincoln, Nebraska.
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Progress 12/01/10 to 11/30/11
Outputs
OUTPUTS: The focus of this project is to define the genetic loci in wheat that regulate ideal leaf wax content and varying chemical composition in relation to improved drought tolerance. The goal is to define the importance of leaf wax in increasing yield, and reducing plant water use during drought and high temperature stress. Additionally the project will produce molecular plant breeding tools that can be used to rapidly breed the beneficial high leaf wax trait into new drought tolerant wheat cultivars. To this end, we have completed two year of yield studies at 3 locations in Texas and 1 in Sonora, Mexico. Each site had 2 duplicate trials of the same two mapping populations. The first trial was treated with control or ideal water conditions, while the second drought treated trial had no irrigation following the beginning of flower initiation. Phenotypic yield component data, end-use quality data and physiological data were collected. The later included canopy temperature, photosynthesis, and the total and chemical composition of the leaf wax was collected. At this stage, the yield and quality analysis are completed, the chemical composition analysis of the leaf wax for each individual of the genetic mapping population is currently in progress. Additionally the mapping population is currently being digitally genotyped for single nucleotide polymorphisms and mapped with single sequence repeats. We have conveyed the results of this project in three presentations to the Texas Heat Producers Board (TWPB). The TWPB is the Texas wheat producers checkoff, governing, and research funding board. These presentations were: 1. Hays D, 2011. The genetic overlap between leaf epicuticular wax and reproductive stage heat and drought stress tolerance in wheat; 2. Thompson S, Hays D, Washington-Allen R. 2011. Estimating changes in above-and below-ground 3-D vegetation structure in a wheat using ground-penetrating radar and terrestrial laser scanning; 3. Chick C, Hays D. 2011. Association Mapping leaf epicuticular wax and drought stress tolerance in wheat. We have also conveyed our results to CIMMYT (International Maize and Wheat Improvement Center) colleagues Drs. Mathew Reynolds, Ravi Singh, Arun Joshi. Drs. Suchismita Mondal, Richard E. Mason (in Agricultural Sciences) are Ph.D. students of principal investigators program and this project. They are now or recent plant breeders with Dr. Ravi Singh at CIMMYT. Dr. Richard E. Mason is now the Assistant Professor of Wheat Breeding at the University of Arkansas and a recent USDA-NIFA grant awardee. To date, our project has graduated four M.S. students, Julie Rothe, Henry Awika, Ashima Poudel, and Francis Beecher, and three Ph.D. students Richard Mason, Suchismita Mondal, and Arlene Pacheco in the Agricultural Sciences. Five additional Ph.D. students will complete there Ph.D.s prior to the end of this grant, Francis Beeacher, Chris Chick, Trevis Huggins, Suheb Mohammed, and Padma Sengadon all in the Agricultural Sciences. PARTICIPANTS: This project has graduated four M.S. students, Julie Rothe, Henry Awika, Ashima Poudel, and Francis Beecher, and three Ph.D. students Richard Mason, Suchismita Mondal, and Arlene Pacheco in the Agricultural Sciences. Five additional Ph.D. students will complete there Ph.D.s prior to the end of this grant, Francis Beeacher, Chris Chick, Trevis Huggins, Suheb Mohammed, and Padma Sengadon all in the Agricultural Sciences. These students have been funded on $389,000 in additional graduate research fellowships from Texas A&M University, and Monsanto. TARGET AUDIENCES: The results of this project have been conveyed to the Texas Wheat Producers Broad, the Southwest Farm Press, colleagues in the Consultative Group for International Agriculture Research at the International Center for Maize and Wheat Research and audiences of the Crop Science Society of America is the form of twelve oral presentations and personal meetings with colleagues. The results of this research will also be presented to colleagues in India, Bangladesh and Nepal as part of the USIEF-US-India-Bangladesh Regional Fulbright Research Fellowship awarded to the principal investigator of this project Dirk. Hays. The project will conduct collaborative parallel research on the role of high leaf wax in heat tolerance in wheat with Dr. V.K Mishra, Banaras Hindu University in India and Dr. NCD Barma at the Bangladesh Agricultural Research Institute from January to August 2012. PROJECT MODIFICATIONS: The project is on track to complete its objectives. No major changes, delays, or omissions in the project goals are anticipated.
Impacts
The results of this project have identified unique genetic loci in wheat that regulate improved drought tolerance. Three genetic loci have been identified that double the leaf wax content on leaves, while maintaining a 4 to 6C cooler plant canopy, and increase yield by 25% during drought and heat stress. The project is one track to complete the goals of the project. Two of high leaf wax genetic loci identified also regulate staygreen during drought and durable resistance to leaf rust. We have identified the mechanism for the later. The project has developed rapid screening methods to breed and select new wheat germplasm and cultivars with ideal leaf wax for deduced water and irrigation use, improved consistency in end-use bread and wheat flour product quality, and increased yield during drought. These tools will speed combination of high leaf wax with other drought and heat stress adaptive traits in new wheat cultivars. The tools can and are being used in breeding other economically important crops such as sorghum, corn, and black-eye peas. The principal investigator of the project Dirk B. Hays, was recently awarded a USIEF-US-India Bangaldesh Regional Fulbright Fellowship ($54,000) to conduct collaborative parallel research on the role of high leaf wax in heat tolerance in wheat with Dr. V.K Mishra, Banaras Hindu University in India and Dr. NCD Barma at the Bangladesh Agricultural Research Institute from January to August 2012.
Publications
- Meeks, M., Murray, S. C. , Hague, S. , Hays D., Ibrahim, A. M. H.. 2011. Genetic Variation for Maize Epicuticular Wax Response to Drought Stress at Flowering, J. Agronomy & Crop Science (2011) ISSN 0931-2250.
- Awika H, Rooney W, Hays D. 2011. Determining the genetic overlap between leaf epicuticular wax, canopy temperature depression, and the staygreen trait in a sorghum RIL population. ASA,CSSA,SSA, San Antonio, TX.
- Mohammed S, Huggins T, Beecher F, Chick C, Poudel A, Hays D. 2011. Leaf Epicuticular Wax Deposition Study and Mapping Waxy QTL for Wheat Drought Lines. ASA,CSSA,SSA, San Antonio, TX.
- Mason, R.E., Mondal, S., Beecher, F.W, Hays, D.B. 2011 Genetic loci linking improved heat tolerance in wheat (Triticum aestivum L.) to lower leaf and spike temperatures under controlled conditions. Euphytica. 180: 181-194.
- Beecher F, Hays D. 2011. Association between ethylene and wax production in wheat (Triticum aestivum). ASA,CSSA,SSA, San Antonio, TX.
- Thompson S, Brademan W, Barber B, Delgado A, Austin M, Hays D, Washington-Allen R. 2011. Estimating changes in above-and below-ground 3-D vegetation structure in a model savanna using ground-penetrating radar and terrestrial laser scanning. ESA Annual Meeting, Austin, Texas.
- Thompson S, Brademan W, Barber B, Delgado A, Austin M, Hays D, Washington-Allen R. 2011. Estimating changes in above-and below-ground 3-D vegetation structure in a model savanna using ground-penetrating radar and terrestrial laser scanning, Plant Biology, St. Paul, MN.
- Poudel A, Beecher F, Mohammed S, Ibrahim A, Hays D. 2011. Identification of genetic loci regulating bread making quality stability in wheat in a Halberd x Len recombinant inbred line population. ASA,CSSA,SSA, San Antonio, TX.
- Huggins T, Hays D, Mohammed S. 2011 Changes In Epicuticular Wax In Wheat During Reproductive Development In Response to Heat Stress. ASA,CSSA,SSA, San Antonio, TX.
- Huggins T, Hays D.. 2011. Change in epicuticular wax levels in wheat lines in response to heat stress. Plant Biology, Minneapolis, Mn.
- Arlene P, Hays D. 2011. Increased Wax Deposition on the Epicuticular Layer of Wheat Leaves May Lower Incidence of Leaf Rust Infection. Plant Biology, Minneapolis, Mn.
- Pacheco Arlene, Hays Dirk. 2011. Increased Wax Deposition on the Epicuticular Layer of Wheat Leaves May Lower Incidence of Leaf Rust Infection. Field Crops Rust Symposium, San Antonio, Tx.
- Hays D, 2011. The genetic overlap between leaf epicuticular wax and reproductive stage heat and drought stress tolerance in wheat, Texas Wheat Producers Board, Vernon, Texas.
- Thompson S, Hays D, Washington-Allen R. 2011. Estimating changes in above-and below-ground 3-D vegetation structure in a model savanna using ground-penetrating radar and terrestrial laser scanning, Texas Wheat Producers Board, Vernon, Texas.
- Chick C, Hays D. 2011. Association Mapping leaf epicuticular wax and drought stress tolerance in wheat. Texas Wheat Producers Board, Vernon, Texas.
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Progress 12/01/09 to 11/30/10
Outputs
OUTPUTS: Drought and heat stress are the primary reason for the $684 million loss in the 2006 Texas wheat harvest. While wheat has numerous adaptations to heat and drought stress, some decrease yield, such as during hot and dry conditions when low stomatal conductance and impaired energy dissipation cause premature senescence in many wheat cultivars. The plant cuticle can however limit transpirational water loss by reflecting excess light and heat while maintaining a tempered canopy with adequate turgor during drought for improved growth and reproduction. Our breeding strategy is to reduce irrigation and maintain yield during drought and heat stress by optimizing the leaf cuticle layer. The cuticle is comprised of an outer epicuticle, the cuticle proper, and the wall embedded cuticular layer, each composed of complex of polymeric cutins and long-chain hydrocarbon waxes. The importance of the layers and varied composition to stress tolerance is not understood. Our objective is to define their importance by linking the QTLs that regulate the individual layers and varied composition to yield stability during reproductive heat and drought stress in wheat. We have begun to achieve this objective by: 1. QTL mapping a population of 180 lines derived from an Australian cultivar Halberd with three cuticle layers versus a prominent US cultivar with only a single epicuticular layer Len and, 2. In collaboration with CIMMYT, an association-mapping panel of 294 drought tolerant wheat lines from CIMMYT, Australia, and adapted landraces are being evaluated by this project, and colleagues in drought prone Mexico, South Asian, and Middle Eastern environments. Objective 1: The QTL mapping population was planted in two locations in 2010 at College Station, and Uvalde, Texas. In the field, the population was planted over drip irrigation in two zones, where 2 reps of the population were well water, while the second set could be treated with limited irrigation. The wheat-growing season in 2010 had very significant rainfall at both locations. Thus the drought stress experiment in the field was converted to a reproductive stage heat stress experiment. High temperature stress was significant during the flowering and early grain fill period. We are using yield stability and its association to epicuticular wax as phenotypic data for QTL mapping. The population was also planted in control greenhouse conditions under well-watered and limited water during the flowering and early grain development. The extracted wax from these experiments is currently being analyzed. Objective 2: The association-mapping panel was planted in three delayed plantings by CIMMYT at Obregon, Mexico over drip irrigation. Each planting consisted of one block of two replications under well-watered conditions and a second block of two replications under water-stress conditions. As part of this project, we travel to CIMMYT and collected two replications for epicuticular wax from flag leaves for both well watered and water stress conditions. Leaf samples for wax extraction were collected at 10 DAP in March and April 2010 for two independent plantings. The extracted wax is currently being analyzed PARTICIPANTS: Collaborators: Mathew P. Reynolds, Wheat Physiologist, Global Wheat Program CIMMYT, Mexico; Ravi Singh, Wheat Breeder, Global Wheat Program CIMMYT, Mexico; E. Ann Ellis, M.S., Sr. Research Associate, Texas A&M University Microscopy Center: Postdoctoral Fellows: Fei Wang, Postdoctoral Research Associate, Texas A&M University, 8-2010-present; Students: Suchismita Mondal, Ph.D. Plant Breeding, Texas A&M University ; 8-2006- present; Arlene Pacheco Ph.D. Molecular and Environmental Plant Sciences, Texas A&M University; 12-2005-present; Francis Beecher Ph.D. Plant Breeding, Texas A&M University, 8-2009 - present; Sean Thompson Ph.D. Plant Breeding, Texas A&M University, 11-2010 - present; Chris Chick Ph.D. Molecular and Environmental Plant Sciences, Texas A&M University, 8-08- present; Suheb Mohammed Ph.D. Plant Breeding, Texas A&M University, 8-2009-present; Ashima Poudol, M.S. Plant Breeding, Texas A&M University, 1-2010-present; Trevis Huggins Ph.D. Molecular and Environmental Plant Sciences, Texas A&M University, 8-2010- present; Brijesh Angira, Ph.D. Plant Breeding, Texas A&M University, 8-2010- present. TARGET AUDIENCES: U.S. Wheat Producers, Texas Wheat Producers, Syngenta, Monsanto, Bayer Crop Sciences, Grupo Bimbo, General Mills, PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
For the first objective, thirteen wheat cultivars were also subjected to a 2-day heat treatment at 38C at 10 days after pollination (DAP). Leaf cuticular waxes, canopy temperature depression, stomatal conductance were estimated during high temperature stress. At maturity the percent reduction in yield components in each cultivar was calculated. A set of 121 recombinant inbred lines (RIL) population derived from a cross of heat tolerant wheat cultivar Halberd and heat susceptible wheat cultivar Karl 92 was utilized for QTL mapping. The RIL population received a 2-day short-term high temperature stress at 38C at 10DAP in 2008 and a long-term high temperature stress at 38C from 10DAP until maturity in 2009. Leaf cuticular waxes were estimated at 10DAP in the greenhouse. Heat susceptibility indexes for main spike yield components were estimated at harvest in the greenhouse. The RIL population was planted in College Station, Texas in 2009 and 2010 and in Uvalde, Texas in 2010. Leaf cuticular waxes were estimated at 10DAP and leaf/spike temperatures were recorded during grain filling in the field. Yield components were estimated after harvest from the field. Significant genotypic differences were observed for leaf cuticular waxes and leaf temperature depression within the wheat cultivars. The heat tolerant cultivars Kauz and Halberd had significantly cooler canopies and high leaf cuticular wax content of 2.91mg/dm2 and 2.36mg/dm2 respectively. Leaf cuticular wax content at 10DAP correlated positively with leaf temperature depression and negatively with percent reduction in kernel number. The RIL population segregated for leaf cuticular waxes and had significant association of leaf cuticular waxes with leaf temperature depression and HSI of yield components during short-term heat stress. Overall ten significant QTL were identified for leaf cuticular waxes each explaining 8-19 percent of the variation respectively. Stable QTL for leaf cuticular waxes were located on chromosome 5A and 1B and co-localized with QTL for leaf/spike temperature depression and HSI for kernel weight and single kernel weight of main spike. The results suggest that leaf cuticular waxes may reduce leaf temperatures and improve adaptation during high temperature stress. In 2011, the RIL and association-mapping panel for objectives 1 and 2 have been planted at four locations in Texas (Uvalde, College Station, and Chilicothe, Texas, and Obregon, Mexico). At each location, each population has been planted as two sets of two replications over drip irrigation. The drip irrigation is separated into two zones at each location, one well watered and under drought stress conditions. Each line will be replicate sampled for flag leaf epicuticular and cuticular wax at 10 DAP and correlated with yield components, yield component stability, canopy temperature depression, and spectral reflectance indices.
Publications
- Mason R.E., Mondal S., Beecher F., Ibrahim A., Hays D.B. 2010. Quantitative loci regulating yield maintenance under reproductive stage heat stress in wheat. Euphytica 174: 423-436.
- Ali M.,, Ibrahim A.H.,1Hays,D.B., Ristic Z. Fu J. 2010. Response of Wild Tetraploid Wheat (Triticum turgidum L.) to Heat Stress. J. Crop Improv. 24:228-243.
- Reynolds M.P., Hays D.B.2 Chapman S. 2010. Breeding for adaptation to heat and drought stress, In: Climate change and crop production, Reynolds M.P. (Ed.), CABI Inc.
- Francis Beecher, Christopher Chick, Suheb Mohammed, Ashima Paudel, Trevis Huggins, Amir Ibrahim, Dirk Hays. 2010. Investigation of the Role of Epicuticular Wax On Heat and Drought Tolerance in Wheat (Triticum aestivum). ASA, CSSA, SSSA Annual Meeting, Long Beach ,CA 294-6.
- Suchismita Mondal, Dirk Hays. 2010. Molecular Mapping and Characterization of Flag Leaf Wax in Wheat (Triticum aestivum L.). ASA, CSSA, SSSA Annual Meeting, Long Beach ,CA 65-15.
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