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).
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).
A recently developed GIS-based time surface visualization system was used to create year-long visualizations of a decade of environmental data for the 2003-2012 interval. The year-long time surfaces provide a novel presentation of the interactions among environmental factors over daily and seasonal time intervals. Efforts toward implementation of the method using open-source software are underway. The development of resistant cotton germplasm to a disease caused by a recently discovered and highly virulent fungus strain of Fusarium wilt (FOV race 4) is critical to ensure the profitability of this crop in the San Joaquin Valley of California. We increased progeny and germplasm at the Plant Stress and Germplasm Development Research Unit and at the Winter Nursery in Tecoman, Colima, Mexico, to conduct field and greenhouse evaluations for FOV race 4 resistance. In cooperation with the University of California cooperators, more than 8000 cotton plants from around 400 entries were evaluated for resistance levels to FOV race 4 in infested field and greenhouse artificial inoculation studies. These studies revealed that the genes active in the plant disease-response varied with environmental conditions and with the origin of the genetic backgrounds of cottons. Several resistant FOV race 4 Pima germplasm will be released to expand the genetic base available to cotton breeders for development of Fusarium-resistant varieties. In addition, DNA of genomic regions of two cotton chromosomes (11 and 21) were examined for the presence of disease resistance genes from sequences of bacterial artificial chromosome DNA information of the cultivar Acala Maxxa. To determine genetic variation of maize germplasm collections to heat stress, we have evaluated the response of 537 maize accessions and 202 double haploid (DH) lines generated by USDA-ARS GEM Project to heat stress in field conditions in 2014 season. Two replicates of 537 maize accessions and 1 replicate of DH lines were planted and maintained under well-watered conditions via a subsurface-irrigation system. Heat tolerant/sensitive responses of maize plants to heat stress were visually evaluated 7-10 days after each major heat wave event had occurred. Major heat sensitive/tolerant traits of maize plants were recorded at both vegetative and reproductive stages. Field results showed that there are great genetic variations in the responses of maize accessions to heat stress. Maize accessions that are either highly tolerant or sensitive to heat stress were identified. Heat tolerance of these lines will be reevaluated under controlled conditions. Lines with confirmed specific heat tolerant traits will be used to make crosses for generating mapping populations in next season. cDNAs of atFtsH11 homologous genes from 2 other plant species were PCR amplified and cloned. Cloning of cDNA of atFtsH11 homologous from other 2 crop species is still under way. The cDNA clones will be introduced into the binary vector respectively, and resulting constructs will be introduced into the ftsh11 mutant via Agrobacterium-mediate transformation approach. A label-free quantitative proteomics approach was used to study the functional proteins altered in the mid-mature (65-70 days post-anthesis) peanut seed grown under water-deficit stress conditions. A pod-specific proteome database was developed and identified 93 non-redundant, statistically significant, and differentially expressed proteins between well-watered and drought-stressed seeds. Mapping of these differential proteins revealed three candidate biological pathways (glycolysis, sucrose and starch metabolism, and fatty acid metabolism) that were significantly altered due to water-deficit stress. Differential accumulation of proteins from these pathways provides insight into the molecular mechanisms underlying the observed physiological changes, which include reductions in pod yield and biomass, reduced germination, reduced vigor, decreased seed membrane integrity, increase in storage proteins, and decreased total fatty acid content. Some of the proteins encoding rate-limiting enzymes of biosynthetic pathways could be utilized by breeders to improve peanut seed production during water-deficit conditions in the field.
1. Winning the fight against Fusarium wilt in cotton. Fusarium wilt [Fusarium oxysporum f. sp. vasinfectum (FOV)] represents the most serious threat to cotton production in California. The FOV race 4 fungus can survive for long periods in the soil, making it impossible to eradicate. Resistant cotton varieties are the most effective method to control yield loss. To speed the development of resistant varieties, molecular markers such as SSR can be used in assisting breeding efforts. Analyses of Pima cottons by ARS researchers at Lubbock, Texas, and University of California cooperators identified a major resistance gene to FOV race 4 in Pima-S6 germplasm, and molecular markers associated with this resistance. These SSR markers represent a new tool that can be used in marker-assisted selection techniques for breeding FOV race 4 resistance into elite cotton varieties.
2. See who is 'burning' under the heat. Genetic differences determine whether plants survive under 'hot' conditions. Scientists within the Plant Stress and Germplasm Development Unit in Lubbock, Texas, have evaluated maize lines for their responses to heat stress under field conditions. The results showed large genetic variation for heat tolerance among maize lines. Understanding the cause for such difference will help breeders develop maize lines with enhanced heat tolerance.
3. Heat tolerance gene identified. Plants reduce photosynthesis under high temperatures, leading to a decrease in biomass production and yield. FtsH11 has been found to play an essential in maintaining normal photosynthesis at moderate high temperature of 30 degrees C or above. Scientists within the Plant Stress and Germplasm Development Unit in Lubbock, Texas, cloned FL-cDNA atFtsH11 homologous genes from other plant species, providing an initial step in the functional characterization of crop FtsH11 proteases in maintaining thermostability of chloroplasts under moderately high temperature stress, enabling plants to better cope with daily and seasonal temperature fluctuations and sustain productivity under unfavorable environments.
Fang, H., Zhou, H., Sanogo, S., Flynn, R., Percy, R.G., Hughs, S.E., Ulloa, M., Jones, D.C., Zhang, J. 2013. Quantitative trait locus mapping for Verticillium wilt resistance in a backcross inbred line population of cotton (Gossypium hirsutum x Gossypium barbadense) based on RGA-AFLP analysis. Euphytica. 194:79-91.
Hutmacher, R.B., Ulloa, M., Wright, S.D., Campbell, B.T., Percy, R.G., Wallace, T., Myers, G., Bourland, F., Weaver, D., Chee, P., Thaxton, P., Zhang, J., Smith, W., Dever, J., Kuraprthy, V., Bowman, D., Jones, D., Burke, J.J. 2013. Elite-upland cotton germplasm-pool assessment of fusarium wilt (FOV) resistance in California. Agronomy Journal. 105:1635-1644.
Emgamberdiev, S.S., Salakhudinov, I.B., Abdullaev, A., Ulloa, M., Saha, S., Radjapov, F., Mullaohunov, B., Mansurov, D., Jenkins, J.N., Abdurakhmonov, I.Y. 2014. Detection of Fusarium oxysporum f. sp. vasinfectum race 3 by single-base extension method and allele-specific polymerase chain reaction. Canadian Journal of Plant Pathology. 36(2):216-223.
Ulloa, M. 2014. The diploid D genome cottons (Gossypium spp.) of the new world. In: Abdurakhmonov, I.Y., editor. World Cotton Germplasm Resources. Volume 8. Rijeka, Croatia:Intech. p. 201-229.
Burke, J.J., Chen, J., Burow, G.B., Rosenow, D., Mechref, Y., Payton, P.R., Xin, Z. 2013. Leaf dhurrin content is a quantitative measure of the level of pre- and post-flowering drought tolerance in sorghum. Crop Science. 53(3):1056-1065.
Percy, R.G., Frelichowski, J.E., Arnold, M., Campbell, B.T., Dever, J., Fang, D.D., Hinze, L.L., Main, D., Scheffler, J.A., Sheehan, M., Ulloa, M., Yu, J., Yu, J. 2014. The U.S. National Cotton Germplasm Collection – its Contents, Preservation, Characterization, and Evaluation. In: Abdurakhmonov, I. Editor. World Cotton Germplasm Resources. Rijeka, Croatia: InTech. 167-201. Available: http://www.intechopen.com/books/world-cotton-germplasm-resources/the-u-s-national-cotton-germplasm-collection-its-contents-preservation-characterization-and-evaluation.
Baker, J.T., Gitz, D.C., Payton, P.R., Broughton, K.J., Bange, M.P., Lascano, R.J. 2014. Carbon dioxide control in an open system that measures canopy gas exchanges. Agronomy Journal. 106(3):789-792.
Mittal, A., Gampala, S.S., Ritchie, G.L., Payton, P.R., Burke, J.J., Rock, C.D. 2014. Related to ABA-Insensitive3(ABI3)/Viviparous1 and AtABI5 transcription factor coexpression in cotton enhances drought stress adaptation. Plant Biotechnology Journal. 12(5):578-589.
Reddy, S., Liu, S., Rudd, J.C., Xue, Q., Payton, P.R., Finlayson, S.A., Mahan, J.R., Akhunova, A., Holalu, S.V., Lu, N. 2014. Physiology and transcriptomics of water-deficit stress responses in wheat cultivars TAM 111 and TAM 112. Journal of Plant Physiology. 171(14):1289-1298.
Xue, Q., Rudd, J.C., Liu, S., Jessup, K.E., Devkota, R.N., Mahan, J.R. 2014. Yield determination and water-use effenciency of wheat under water-limited conditions in the U.S. Southern High Plains. Crop Science. 54(1):34-47.