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Sorghum breeding program for biofuel production
Biofuels are a major contributor to the energy security of the United States, to the economic growth of Iowa and to the reduction of greenhouse gasses emission. The Energy Independence and Security Act (2007) established that 36 billion gallons of biofuels per year had to be produced by 2022. In 2018, 16 billion gallons of ethanol were produced from maize, but maize-based ethanol cannot supply the total demand and it has detrimental implications for food and feed supplies. Therefore, other sources, such as lignocellulosic feedstock, need to be developed.
In 2008, Dr. Salas Fernandez initiated the sorghum breeding program for biofuel production at Iowa State University. The main goal is to conduct research for the development of sorghum germplasm for biofuel production adapted to Iowa. The breeding program is centrally located in Ames, IA, with winter nursery activities in Puerto Rico and three testing locations in Iowa were experimental hybrids are evaluated every year.
Sorghum ethanol yields vary depending on the type of sorghum cultivated. Sweet sorghums can produce 900 gallons/acre, if we consider a standard composition, yields of 16 Tn of dry matter/ha and 90% conversion efficiency. Our yield trials demonstrate that biomass sorghum can produce up to 1,120 gallons/acre as a lignocellulosic feedstock, considering our highest yields of 35 Tn dry matter/ha, a standard composition and a 90% conversion efficiency. Therefore, sorghum could become the preferred bioenergy crop, considering its high yield potential and the additional benefit of low input use, since it requires less nitrogen and water than corn.
In addition to the ethanol production from corn grain, commercial lignocellulosic biorefineries are processing corn-derived biomass, a dry and low volume feedstock. Recent evidence suggests that the greenhouse gas (GHG) benefit of cellulosic ethanol from corn stover is marginal relative to fossil fuel production. Therefore, sorghum biomass could be used as a new source of cellulosic fuel with net GHG savings relative to corn stover. The advantage will be to produce biofuel with a reduced environmental impact and without competing for food production. Considering that storage and transportation of high-tonnage biomass with high water content is a major limitations to the development of a strong bioeconomy, anaerobic digestion (on-farm or at centralized facilities) is considered a promising conversion technology to generate biogas. The ISU sorghum breeding program is developing novel germplasm for these goals and processing methods.
Funding: R.F. Baker Center for Plant Breeding, Iowa Crop Improvement Association
Photosynthesis in sorghum under non-stress, cold and drought stress
Carbon assimilation through photosynthesis is the basis of crop productivity. However, increases in crop yield achieved in the last 50 years have not been attributed to changes in photosynthetic capacity. The complex genetic architecture of C assimilation and the lack of correlation between grain yield and photosynthesis were the most important arguments to postpone significant investments in this scientific area. The advancement of "omics" technology, high-throughput phenotyping methods and biofuels has significantly changed the paradigm. Considering there is a direct association between photosynthetic efficiency and biomass yield, the discovery and exploitation of the genetic architecture controlling C assimilation could have a significant impact on biomass yield for biofuel production. Dr. Salas Fernandez and her team are investigating genes/alleles associated with higher leaf photosynthetic capacity under non-stress, cold and drought stress using both field and controlled condition experiments.
Several genomic regions associated with gas exchange and chlorophyll fluorescence parameters were discovered and are curently being validated. These studies have demonstrated the existence of natural genetic variation in C fixation that could be exploited to breed for superior germplasm.
Funding: the United Sorghum Checkoff program, the USDA-DOE Plant Feedstock Genomics for Bioenergy, and National Science Foundation (CAREER) Plant Genomics Research Program.
Plant architecture
Several hormones are involved in the biochemical and physiological responses that determine plant architecture characteristics highly correlated with biomass yield such as plant height, leaf angle, stem diameter, tillering, number of florets, etc. Brassinosteroids, gibberellins and auxins have the strongest impact without severe undesirable pleiotropic effects. Identifying genes involved in biosynthetic and signaling pathways of these groups of hormones and the effects of alternative alleles will reveal the allelic combination to obtain a particular plant type. Sorghum germplasm offers a vast genetic diversity to dissect plant architecture traits and identify genes/alleles controlling specific characteristics.
We have conducted genome-wide and candidate gene association studies to characterize the genetic architecture of plant height, stem diameter, leaf angle, exsertion, panicle lenght, internode number, flowering time, seed number per panicle and tiller number using the Sorghum Association Panel. We have discovered genomic regions and candidate genes that are currently being validated. With the need to produce more food, feed and fuel in the same or smaller area, and considering climate change, manipulating genes to create desirable plant types in a shorter period of time will be essential in breeding programs. Sustainable production of biofuel will also require using fewer inputs, in more marginal lands, and therefore producing a specific sorghum plant for that production system will be very valuable as well.
Funding: R.F. Baker Center for Plant Breeding (ISU)
Google Scholar
Xiang L, Bao Y, Tang L, Ortiz D, M.G. Salas-Fernandez. (2019). Automated morphological traits extraction for sorghum plants via 3D point cloud data analysis. Computers and Electronics in Agriculture 162: 951-961.
Zhou Y., S. Srinivasan, S.V. Mirnezami, A. Kusmec, Q. Fu, L. Attigala, M.G. Salas Fernandez, B. Ganapathysubramanian, and P.S. Schnable. (2019). Genome-wide association study for sorghum panicle architecture using semi-automated, high-throughput feature extraction from RGB images. Plant Physiology
Bao Y., L. Tang, M. Breitzman, M.G. Salas Fernandez, and P.S. Schnable. (2019). In-field robotic phenotyping of sorghum plant architecture using stereo vision. J. Field Robotics 35: 397– 415. https://doi.org/10.1002/rob.21830
Ortiz, D., A. Litvin, and M.G. Salas Fernandez. (2018). A low-cost automated irrigation system for precise high-throughput phenotyping in drought stress studies. PLoS ONE 13 (6): e0198546. https://doi.org/10.1371/journal.pone.0198546
Mantilla Perez, M.B. and M.G. Salas Fernandez. (2017). Differential manipulation of leaf angle throughout the canopy: current status and prospects. (Darwin Reviews). J. Exp. Bot. 68 (21-22): 5699-5717. https://doi.org/10.1093/jxb/erx378.
Roby, M., M.G. Salas Fernandez, E.A. Heaton, F. Miguez, and A. VanLoocke. (2017). Biomass sorghum and maize have similar water-use efficiency under non-drought conditions in the rain-fed Midwest U.S. Agriculural and Forest Meteorology Journal 247: 434-444. https://doi.org/10.1016/j.agrformet.2017.08.019.
Ortiz, D., J. Hu and M.G. Salas Fernandez. (2017). Genetic architecture of photosynthesis in Sorghum bicolor under non-stress and cold stress conditions. J. Exp. Bot. 68(16):4545-4557. https://doi.org/10.1093/jxb/erx276.
Salas Fernandez, M.G., Y. Bao, L. Tang, P.S. Schnable. (2017). A high-throughput field-based phenotyping technology for tall biomass crops. Plant Physiology 174 (4): 2008-2022. DOI: 10.1104/pp.17.00707.
Zhao, J., M.B. Mantilla Perez, J. Hu, and M.G. Salas Fernandez. (2016). Genome-wide association study for nine plant architecture traits in Sorghum bicolor. The Plant Genome 9 (2): 1-14. doi:10.3835/plantgenome2015.06.0044.
Li, L., W. Zheng, Y. Zhu, H. Ye, B. Tang, Z.W. Arendsee, D. Jones, R. Li, D. Ortiz, X. Zhao, C. Du, D. Nettleton, M.P. Scott, M.G. Salas-Fernandez, Y. Yin, and E.S. Wurtele. (2015). QQS orphan gene regulates carbon and nitrogen partitioning across species via NF-YC interactions. Proc. Natl. Acad. Sci. USA 112(47):14734-14739.
Salas Fernandez, M.G., K. Strand, M. Hamblin, M. Westgate, E. Heaton, and S. Kresovich. (2015). Genetic analysis and phenotypic characterization of leaf photosynthetic capacity in a sorghum diversity panel. Genet. Resour. Crop Evol. 62:939-950.
Matilla Perez, M.B., J. Zhao, Y. Yin, J. Hu, and M.G. Salas Fernandez. (2014). Association mapping of brassinosteroid candidate genes and plant architecture in a diverse panel of Sorghum bicolor. Theor. Appl. Genet. 127(12):2645-2662.
Salas Fernandez, M.G., G. Schoenbaum, and S. Goggi. (2014). Novel germplasm and screening methods for early cold tolerance in sorghum. Crop Sci. 54(6):2631-2638.
Salas Fernandez, M.G., J. Okeno, E. Mutegi, A. Fessehaie, and S. Chalfant. (2014). Assessment of genetic diversity among sorghum landraces and their wild/weedy relatives in western Kenya using simple sequence repeat (SSR) markers. Conserv. Genet. 15:1269-1280.
Salas Fernandez, M.G. (2011). Sorghum: an alternative biomass feedstock for ethanol production in the Midwest. Aspects of Applied Biology 112: 93-98. Biomass and Energy Crops IV Conference. Urbana/Champaign, Illinois, USA.
Yan, J., Bermudez Kandianis, C., Harjes, C.E., Bai, L., Kim, E., Yang, X., Skinner, D., Fu, Z., Mitchell, S., Qing, L., Salas Fernandez, M.G., Zaharieva, M., Babu, R., Fu, Y., Palacios, N., Li, J., Dellapenna, D., Brutnell, T., Buckler, E.S., Warburton, M.L., Rocheford, T. (2010). Rare Genetic Variation at CrtR-B1 Increases β-carotene in Maize Grain. Nature Genetics 42(4): 322-327.
Salas Fernandez, M.G., P.W. Becraft, Y. Yin and T. Lübberstedt. (2009). From dwarves to giants: plant height manipulation for biomass yield. Trends Plant Sci. 14 (8): 454-461.
Salas Fernandez, M.G., I. Kapran, S. Souley, M. Abdou, I. H. Maiga, C. Acharya, M. T. Hamblin, and S. Kresovich. (2009). Collection and characterization of yellow endosperm sorghums from West Africa for biofortification. Genet. Resour. Crop Evol. 56: 991-1000.
Salas Fernandez, M.G., M.T. Hamblin, L. Li, W.L. Rooney, M.R. Tuinstra, and S. Kresovich. 2008. QTL analysis of endosperm color and carotenoid content in sorghum grain. Crop Sci. 48:1732-1743.
Hamblin, M.T., M.G. Salas Fernandez, M.R. Tuinstra, W.L. Rooney, and S. Kresovich 2007. Sequence variation at candidate loci in the starch metabolism pathway in Sorghum bicolor: prospects for linkage disequilibrium mapping. The Plant Genome S2: S125-S134.
Hamblin, M.T., M.G. Salas Fernandez, A.M. Casa, S.E. Mitchell, A.H. Paterson, and S. Kresovich. 2005. Equilibrium processes cannot explain high levels of short- and medium-range linkage disequilibrium in the domesticated grass Sorghum bicolor. Genetics 171: 1247-1256.
Salas, M.G., S. H. Park, M. Srivatanakul, and R.H. Smith. 2001. Temperature influence on stable T-DNA integration in plant cells. Plant Cell Rep. 20:701-705.
Srivatanakul, M., S.H. Park, M.G. Salas, and R.H. Smith. 2001. Transformation parameters enhancing T-DNA expression in kenaf (Hibiscus cannabinus). J. Plant Physiol. 158:255-260.
Park, S.H., B.M. Lee, M.G. Salas, M. Srivatanakul, and R.H. Smith. 2000. Shorter T-DNA or additional virulence genes improve Agrobacterium-mediated transformation. Theor. Appl. Genet. 101:1015-1020.
Srivatanakul, M., S.H. Park, J.R. Sanders, M.G. Salas, and R.H. Smith. 2000. Multiple shoot regeneration of kenaf (Hibiscus cannabinus L.) from a shoot apex culture system. Plant Cell Reports 19:1165-1170.
Srivatanakul, M., S.H. Park, M.G. Salas, and R.H. Smith. 2000. Additional virulence genes influence transgene expression: transgene copy number, integration pattern and expression. J. Plant Physiol. 157:685-690.
Zapata, C., M. Srivatanakul, S.H. Park, B.M. Lee, M.G. Salas, and R.H. Smith. 1999. Improvements in shoot apex regeneration of two fiber crops: cotton and kenaf. Plant Cell, Tissue and Organ Culture 56: 185-191.