Location: Wheat, Sorghum and Forage Research2012 Annual Report
1a. Objectives (from AD-416):
The long-term objectives of this project are the development of sorghum (Sorghum bicolor) germplasm lines with improved bioenergy, feed, and food value, and the elucidation of genetic, biochemical, and biological factors impacting these characters. Over the next five years, the following specific objectives will be addressed: 1) Identify and evaluate genes to improve sorghum for bioenergy, food, and feed traits, 2) Develop a better understanding of genes and fundamental mechanisms controlling cell wall formation and energy availability, and 3) Develop molecular and other technologies for monitoring sorghum fungal pathogens and determine the effects of sorghum genetic modification for bioenergy on pathogen populations.
1b. Approach (from AD-416):
The project utilizes a diverse set of technologies and approaches that are best delineated by objective: Objective 1 will be addressed primarily using traditional whole-plant plant breeding techniques, animal feeding trials, and established laboratory methods for assessment of feed and bioenergy value. Objective 2 will be addressed using current molecular and biochemistry technologies including PCR, RT-PCR, HPLC, microarrays, GC-MS. Objective 3 incorporates both field-based experiments and current molecular biology technologies. All experiments will utilize sound statistical designs to allow hypothesis testing at established levels of probability.
3. Progress Report:
Sorghum brown midrib (bmr) mutants have been developed which reduce lignin content of biomass, thereby increasing digestibility for livestock and conversion potential for cellulosic ethanol. New brown midrib mutants have been identified from an ARS population at Lubbock, TX and a series of these bmr12 mutants were characterized. These new mutant lines have the potential to provide additional genetic resources to modulate lignin content and composition. Lignin, has been previously implicated in helping plants defend themselves from pathogens. These new bmr lines were screened for susceptibility to stalk rot pathogens, which can reduce yield and contribute to lodging. None of the bmr lines showed increased susceptibility to the pathogen compared to non-modified or wild-type sorghum, and some bmr lines showed increased resistance to the pathogens. These results indicate that genetically reducing lignin concentration in sorghum using bmr mutants for bioenergy feedstock improvement should not increase susceptibility of sorghum to stalk rot pathogens. (301/03/A) (303/03/B) The waxy mutation reduces amylose starch and increases amylopectin starch concentration in sorghum, and together these changes in starch composition increase the digestibility of sorghum grain for livestock and the conversion efficiency of sorghum grain to ethanol. Near-isogenic lines containing the waxy mutation were developed that are adapted to the northern sorghum region of the USA. Grain from waxy and wild-type lines was screened for fungal pathogen, which can affect grain yield or affect grain quality. The results showed that waxy sorghum lines were not more susceptible to grain infections than wild-type lines. (301/03/C) (303/03/B) Biological controls are important management tools for plant pests and pathogens. Two soil bacteria were identified which have potential as biological control agents, because they inhibit the growth of soil borne fungal pathogens that infect both sorghum grain and stalks. This information may lead to new ways to control these pathogens, which impact both grain and biomass yields. (303/04/A)
1. Identification of Brown midrib 2 (Bmr2) gene. Lignin is the principal component that makes cell walls resistant to breakdown either in livestock digestive systems or in the cellulosic bioenergy conversion process. Brown midrib 2 (bmr2) is a mutant that reduces lignin content and alters lignin composition of sorghum cell walls. The mutation causing bmr2 was identified by scientists at University of Florida and ARS scientists at Lincoln, NE and shown to affect an enzyme involved in lignin synthesis. The function of the enzyme was characterized and determined to be largely responsible for an initial step in lignin synthesis. The bmr2 gene represents a strategic tool that can be used to improve sorghum biomass for bioenergy and forage and potentially could be used in other species.
2. Identification of bacteria with potential for biological control against sorghum pathogens. Fluorescent Pseudomonas bacteria were collected from roots and surrounding soil of different sorghum varieties and a wheat variety grown in two different soil types. These bacteria are able to produce compounds including an antibiotic that inhibit fungi, which cause diseases in sorghum. Two of bacteria isolated from sorghum roots inhibited the growth of five disease-causing fungi. These two bacteria have potential as biological agents to control disease-causing fungi in sorghum.Griess, J., Mason, S., Jackson, D., Galusha, T., Pedersen, J.F., Yaseen, M. 2011. Environment and hybrid influences on rapid visco analysis starch properties of food-grade grain sorghum. Crop Science. 51(4):1757-1766.
Lee, S.J., Warnick, T.A., Pattathill, S., Alveo-Maurosa, J.G., Serapiglia, M.J., Young, N.F., Schnell, D.J., Smart, L.B., Hahn, M.G., Pedersen, J.F., Mccormick Ford, H., Brown, V. 2012. Biological conversion assay for determining plant feedstock quality. Biotechnology for Biofuels. 5:5.
Saballos, A., Sattler, S.E., Sanchez, E., Foster, T., Xin, Z., Kang, C., Pedersen, J.F., Vermerris, W. 2012. Sorghum Brown midrib 2 (Bmr2) gene encodes the major 4-coumarate Coenzyme A ligase involved in lignin synthesis. Plant Journal. 70:818-830.
Sattler, S.E., Palmer, N.A., Saballos, A., Greene, A.M., Xin, Z., Sarath, G., Vermerris, W., Pedersen, J.F. 2012. Identification and characterization of 4 missense mutations in brown midrib 12 (Bmr12); the caffeic O-methyltranferase (COMT) of sorghum. BioEnergy Research. 5: 855-865. DOI 10.1007/s12155-012-9197.