Location: Wheat, Sorghum and Forage Research2011 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
Sub-objective 1a. Articles describing the chemistry and bioenergy potential of commercially deployed brown midrib genes bmr6 and bmr12 were previously published. Articles describing animal performance are being prepared. New brown midrib mutants have been identified at new loci in a mutant population from USDA ARS Lubbock. Allelism tests, agronomic trials, and fiber chemistry have been completed. Data analyses and summary is underway. Sub-objective 1b. Waxy lines have been provided to collaborators at Kansas State, UC Berkeley, and the Agricultural Research Institute for South-East Region of Russia. A manuscript was published on the contributions of protein and starch chemistry on digestibility, and another submitted describing the effects of waxy sorghum on ethanol production. Field trials have been completed on a set of waxy/wild-type isolines, R-lines, A/B-lines, and another set of isolines with wxa and wxb alleles. Sub-objective 1c. BC1S2 families were planted to the field in spring 2011. Selections will be made at the end of the current growing season. Sub objective 2a. Assessment of bmr-6 gene expression was completed, and analysis of genomic data is ongoing. Sub objective 2b. A sorghum nuclear extract protocol was not developed because promoter elements were not conserved within lignin biosynthetic genes. An alternative strategy was developed using a putative lignin regulatory factor SbMYB68, selected based on comparative genomics. This factor is under investigation. Sub-objective 3a. Procedures for molecular analyses of Fusarium, Alternaria, and Curvularia spp. were established. A manuscript is in preparation for characterization of Alternaria, and Curvularia spp. A procedure for collection of fungi from air was established, and a manuscript for Fusarium spp. published. One-hundred forty four sequences were submitted to GenBank. Sub-objective 3b. Near isogenic plant color line analyses were completed and the resulting manuscript submitted. Screening grain from waxy accessions for fungal colonization, and fungal identifications, approx one-third completed. “Clean” grain for in vitro grain infections assays were produced in the greenhouse. Sub-objective 3c. Stalk rot analyses of bmr near isolines (bmr6, bmr12, bmr6 brm12 double mutants) in two genetic backgrounds using pathogens, Fusarium thapsinum and F. verticillioides, were completed. A similar study using F. proliferatum is underway. Assays to establish conditions for inoculation by Macrophomina phaseolina have been completed and stalk rot analyses with the near isolines are underway. Sub-objective 3d. RFLP analysis of 24 antibiotic producing fluorescent Pseudomonas spp. nearly complete. Inhibition assays with these isolates against five sorghum fungal pathogens completed.
1. Conversion of elite public sorghum strains to brown midrib leads to world-wide distribution and use. Mutant brown midrib strains of sorghum initially released to the public in 1977 had superior digestibility due to reduced lignin content, but were not immediately useful to the seed industry or farmers due to associated detrimental effects such as increased lodging and reduced overall fitness. USDA-ARS researchers at Lincoln, NE, addressed these problems by incorporating two brown midrib genes, bmr-6 and bmr-12 into elite public lines using long-term targeted breeding and research. Research results have demonstrated the ability of hybrid vigor to overcome decreased yield, shown reduced disease incidence to be associated with these genes, and have shown higher biomass ethanol conversion efficiencies to be associated with these genes. Released genetic materials have supported commercial efforts to develop markets for proprietary hybrids throughout the world. Research based on these materials has identified the biochemical and molecular genetic changes responsible for the differences in lignin chemistry leading to the identification of targets for improvement of other bioenergy crops.
Sahoo, L., Schmidt, J.J., Pedersen, J.F., Lee, D.L., Lindquist, J.L. 2010. Growth and fitness components of wild X cultivated Sorghum bicolor (Poaceae) hybrids in Nebraska. American Journal of Botany. 97(10): 1610-1617.