Location: Wheat, Sorghum and Forage Research2013 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:
This five-year project ended February of 2013, and was renewed as project number 5440-21220-032-00D, Genetic Improvement of Sorghum for Non-Grain Energy Uses. The major accomplishments of this project over the past 5 years are summarized here. Sorghum elite lines were bred that incorporated brown midrib (bmr) 6 and 12 mutations to reduce the concentration of the cell wall polymer lignin. These lines were publicly released, which has served as the basis for full range of scientific research on bmr6 and bmr12 from basic cell wall biochemistry to new agricultural applications. The genes encoding three bmr mutant loci were cloned, characterized and discovered to encode enzymes in lignin synthesis. These studies linked phenotypes, mutations, protein levels and enzymatic activity together to provide a complete picture of these bmr lines. This information allows plant breeders to develop strategies to modify lignin content and its composition in sorghum, which also has implications for lignin modification in other bioenergy grasses. Whether bmr6 and bmr12 affected the susceptibility of sorghum to fungal pathogens was evaluated, because lignin accumulation is a common response to pathogens. These studies indicated that using bmr6 and bmr12 to enhance sorghum for bioenergy and livestock feed does not increase disease susceptibility and, for some pathogens, results in increased resistance. Near-isogenic lines containing the waxy mutation were developed for the northern sorghum-growing region of the USA. These lines were shown to have greater digestibility of the grain for livestock feed and conversion efficiency to ethanol. These lines have provided a basis to biochemically characterize Waxy, the sorghum granule-bound starch synthase and its function in amylose synthesis. waxy lines are valuable germplasm for enhancing sorghum grain for conversion to bioenergy, for food processing and for use in research. Grain from waxy and normal sorghum lines was screened for fungal pathogens, which can affect grain yield or grain quality. The results showed that waxy sorghum lines were not more susceptible to grain infections than normal sorghum. Biological controls are important management tools for plant pests and pathogens. Ten soil bacteria isolates 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 sorghum grain and biomass yields.
1. Release of elite brown midrib (bmr6 and bmr12) sorghum lines. Since the first release of elite bmr lines in 2005, over 1200 seed packets from these lines have been distributed without charge and without restrictions on their use, to private companies, universities, and national labs on six continents. These lines are major sources of bmr6 and bmr12 germplasm for the global sorghum community.
2. Demonstrated that food-quality white grain sorghum lines are not more susceptible to diseases. White sorghum grain grown on unpigmented (tan) plants is highly desirable for food and feed uses in contrast to the same white grain grown on pigmented (purple) plants. However, plant pigment has been suggested to protect plants against two fungal diseases: grain mold and head smut. White grain from purple and tan plants was collected from three locations and screened for grain mold infection. The results showed no indication that grain from tan or purple plants had greater levels of infection. In addition, these plants were evaluated for head smut, a common sorghum disease in Corpus Christi, TX. The purple plants were more susceptible to this disease than tan plants at this location. These results indicate that sorghum grain grown on tan plants will not result in greater grain mold and head smut disease incidences, which is valuable information for the development of food-quality grain sorghum.
3. Evaluation of beef cattle grazed on bmr and conventional grain sorghum residue. Brown midrib 12 (bmr12) mutant lines have reduced lignin content in their tissue as compared to conventional plants. Following grain harvest, cattle were grazed on bmr12 and conventional grain sorghum residue, and animal weight gain was monitored. There was a significant (34%) increased in the weight gain of cattle grazing on bmr12 residue relative to cattle grazing on conventional sorghum residue. Therefore, incorporating the bmr trait into grain sorghum increases the value of the residue as a livestock feed.
Funnell-Harris, D.L., Prom, L.K., Pedersen, J.F. 2013. Isolation and characterization of the grain mold fungi, Cochliobolus and Alternaria spp., from sorghum using semi-selective media and DNA sequence analyses. Canadian Journal of Microbiology. 59(2): 87-96.