Progress 07/01/06 to 06/30/09
Outputs
OUTPUTS: The goal of this project is to conduct research in order to create a basis for further work in developing rye cultivars with enhanced allelopathy. Our approach has been to create a synthetic population that varies in allelopathic activity and to estimate the heritability of that trait. In support of that effort, we have developed analytical chemical, in vitro, and in vivo bioassay systems that provide estimates of the allelopathic potential of the line in a field environment. From this data, we have determined that rye allelopathy is a quantitative genetic trait with heritability similar in magnitude to that of grain yield in corn. We have also isolated standards that are being used in the quantitative analysis of rye benzoxazinones, the principal allelopathic natural products in this species. Once this data is obtained, we will determine the repeatability of each assay system (chemical and biological) and determine the best methods for following allelopathic natural product content in rye in the course of breeding for this trait. PARTICIPANTS: A. M. Brooks, Graduate Student; D. Danehower, P.I.; J. P. Murphy, Co-P.I.; J. D. Burton, Cooperator; C. Reberg-Horton, Cooperator; mike Burton, Cooperator; P. Valentine, Student Research Assistant; P. Eure, Student Research Assistant. TARGET AUDIENCES: This work will be of interest to both conventional and organic farmers. Improved weed control methods that do not rely on man-made chemicals could assist both types of farmers in avoiding or minimizing the use of herbicides while increasing soil tilth through the use of an allelopathic cover crop such as grain rye. PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
Bioassay systems using Redroot pigweed (Amaranthus retroflexus) germination, root length and fresh weight biomass were quantified to assess variation in allelopathic activity of rye. Half-sib families were grown at two North Carolina locations and were utilized to obtain estimates of genetic variance and heritability. All measures displayed normal distributions indicating that allelopathy in rye is a quantitative trait. Genetic variation among half-sib families was significant for most measures of redroot pigweed control. Estimates of narrow sense heritability ranged from 0.17-0.21 on per plot basis and 029-0.35 on an entry mean basis. Standard errors for heritability were 0.09-0.11 on a per plot basis and ranged from 0.13-0.15 on an entry mean basis. Higher heritabilities were observed when using quantitative chemical data for benzoxazinone (BX) content. The relationship between allelopathy measured in the bioassay system and the BX content measured in the chemical analysis system was not as strong as anticipated. Based on the presence of significant variation and moderate heritabilities in both the bioassay and chemical analysis systems, it is concluded that selection for allelopathy in rye can be an effective method for improving the allelopathy of grain rye cultivars. It was also concluded that methods for assessment of allelopathic activity in rye need to be improved if this system is to be used as a basis for genetic selection.
Publications
- LaHovary, C., Burton, J.D., Ma, G., Danehower, D.A., Williamson, J.D. and Baerson, S. 2006. Developmental regulation of DIBOA biosynthesis in rye. Weed Science Society of America, 46th Annual Mtg, New York. Feb. 12-16, 2006. Abstracts #138.
- Brooks, A.M., J.D. Burton, M.G. Burton, D. A. Danehower, J. P. Murphy and S.C. Reberg-Horton. Selection for Allelopathy in Rye (Secale cereale). Weed Science Society of North Carolina. Annual Meeting, Raleigh, NC, March 6, 2008.
- Reberg-Horton, C. A. M. Brooks, D. A. Danehower, M. Burton, J. Burton, G. Ma, and P. Murphy. 2008. Breeding rye cover crops for increased allelopathic potential. Fifth World Congress on Allelopathy. Sept. 21- 25, 2008. Saratoga Springs, New York. Abstracts #219.
- Burton, J. D., C. LaHovary, C. Sickler, D.A. Danehower, C. Reberg-Horton, M. Burton, and P. Murphy. 2008. Rye cover crop management to enhance allelopathic weed suppression. Fifth World Congress on Allelopathy. Sept.21- 25, 2008. Saratoga Springs, New York. Abstracts #177.
- Brooks, A. M., D. A. Danehower, Reberg-Horton, C., M. Burton, J. Burton, G. Ma, and P. Murphy. 2008. Selection for allelopathy in Rye (Secale cereale). Fifth World Congress on Allelopathy. Sept. 21- 25, 2008. Saratoga Springs, New York. Abstracts #221.
- Brooks, A. M. 2008. Allelopathy in rye (Secale cereale). M.S. Thesis, North Carolina State U. 125 pp. [electronic resource] located at: http://www.lib.ncsu.edu/theses/available/etd-10242008-090411/unrestri cted/etd.pdf.
- Brooks, A. M., D. A. Danehower, J. P. Murphy, J. D. Burton, C. Reberg-Horton, and M. Burton. 2009. Estimation of Genetic Parameters for Rye Allelopathy (Secale cereale). In preparation.
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Progress 07/01/07 to 06/30/08
Outputs
OUTPUTS: In October 2006, two reps of 150 synthetic rye lines (half-sibs derived from crosses between Wrens Abruzzi and 15 winter rye accessions) and their parental checks were grown at Kinston, NC and Clayton, NC. Field tissue samples were harvested in spring of 2007. Tissues were dried, ground and stored at room temperature for use in subsequent GC, petri dish and greenhouse bioassays. A previously developed greenhouse (GH) bioassay was repeated in late 2007 to evaluate the control of the 150 synthetic lines against 2 weed species - Redroot pigweed and Large crabgrass and to develop estimates of genetic heritability. The GH bioassay was determined to be a successful screening and indicated differences in allelopathic activity among the rye lines. All measures displayed normal distributions indicating that allelopathy in rye is a quantitative genetic trait. Genetic variation among half-sib families was significant for most measures of redroot pigweed control. Estimates of narrow sense heritability ranged from 0.0-0.3 on a per plot basis and 0.1-0.5 on a family-mean basis. Standard errors for heritability were 0.1 on a per plot basis and ranged from 0.1-0.2 on a family mean basis A petri dish bioassay was carried out in 2008. The bioassay used extracts of field grown lines to test allelopathic activity of the synthetic rye lines against Redroot pigweed. This study took place in the Phytotron seed germination chambers. Redroot pigweed seed was germinated under constant light at 30C. Seed germination and root length were recorded after 96 hours as measures of allelopathic activity. Data indicated differences in allelopathic activity of the synthetic rye lines. Estimates of genetic heretability from these experiments is ongoing. In order to have sufficient pure analytical standards of BOA, DIBOA, and DIBOA-glycoside, a system for production and extraction of etiolated rye seedlings was developed and utilized during fall and winter of 2007 and the spring of 2008. Field grown samples are currently being quantified by gas chromatography for benzoxazilinone content in the field grown tissue. In October 2007, two replications of the same 150 synthetic lines and checks were planted at research stations in Kinston, NC and Clayton, NC. Field tissues were harvested in the spring of 2008. Tissues were dried, ground and stored at room temperature for use in subsequent GC, petri dish and greenhouse bioassays. Data derived from analyses of this tissue will be used to determine the effect of time and location on the allelopathic activity of the synthetic rye lines. Beginning in the summer of 2008, GC FID analysis of benzoxazinones, the allelopathic natural products responsible for rye allelopathy, was begun. To date, we have analyzed approximately 350 samples. Once these samples have been analyzed, we will determine the correlation between benzoxazinone content, and allelopathic activity in the petri dish and GH bioassay systems. Results of this work were reported to the NC Weed Science Society in March 2008 and several presentations are planned for the 5th World Congress on Allelopathy in September, 2008. PARTICIPANTS: Nothing significant to report during this reporting period. TARGET AUDIENCES: Nothing significant to report during this reporting period. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
Thew goal of this project is to conduct research that will form the basis for further work in develop rye cultivars with enhanced allelopathy. Our approach is to create a synthetic population that varies in allelopathic activity, to estimate the heritability of that trait, and to develop analytical, in vitro, and in vivo bioassay systems that correlate well with one another and with allelopathy in the field environment. To date, we have developed the bioassay techniques and applied them at least one time to the analysis of allelopathy in the synthetic population. From this data, we have determined that rye allelopathy is a quantitative genetic trait with heritability similar in magnitude to those of grain yield in corn. We are now extending our bioassay work to plant lines produced in a second year of experiments. This will allow us to gain further information about the influence of environment on allelopathy. We have also isolated standards that are being used in the quantitative analysis of rye benzoxazinones, the principal allelopathic natural products in this species. Once this data is obtained, we will determine the repeatability of each assay system (chemical and biological) and determine the best methods for following allelopathic natural product content in rye in the course of breeding for this trait.
Publications
- Brooks, A.M., J.D. Burton, M.G. Burton, D. A. Danehower, J. P. Murphy and S.C. Reberg-Horton. Selection for Allelopathy in Rye (Secale cereale). Weed Science Society of North Carolina. Annual Meeting, Raleigh, NC, March 6, 2008. Abstracts.
- Reberg-Horton, C. A. M. Brooks, D. A. Danehower, M. Burton, J. Burton, G. Ma, and P. Murphy. 2008. Breeding rye cover crops for increased allelopathic potential. The 5th World Congress on Allelopathy. September 21- 25, 2008. Saratoga Hotel and Conference Center, Saratoga Springs, New York, USA. Abstracts.
- Burton, J. D., G. Ma, C. LaHovary, C. Sickler, D.A. Danehower, C. Reberg-Horton, M. Burton, and P. Murphy. 2008. Rye cover crop management to enhance allelopathic weed suppression. The 5th World Congress on Allelopathy. September 21- 25, 2008. Saratoga Hotel and Conference Center, Saratoga Springs, New York, USA. Abstracts.
- Brooks, A.M., J.D. Burton, M.G. Burton, D. A. Danehower, J. P. Murphy and S.C. Reberg-Horton. Progress Towards Selection for Allelopathy in Rye (Secale cereale). The 5th World Congress on Allelopathy. September 21- 25, 2008. Saratoga Hotel and Conference Center, Saratoga Springs, New York, USA. Abstracts.
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Progress 07/01/06 to 06/30/07
Outputs
150 synthetic rye lines (half-sibs derived Wrens Abruzzi and 15 winter rye accessions ) were selected for high allelopathic activity by bioassays conducted in previous work and their parental checks were grown in the NCSU Phytotron at 17C, 10:14 (light:dark) photoperiod and 60% relative humidity. Shoot fresh and dry weights were determined and dried shoots were ground for gas chromatographic analysis and allelopathic bioassays. In October 2006, two replications of the same 150 synthetic lines and checks were planted at Kinston, NC and Clayton, NC. Field tissue samples were harvested in May of 2007, dried, ground and stored at room temperature in double sealed plastic bags for use in subsequent GC and greenhouse bioassays. A greenhouse bioassay system was developed in spring 2007. Preliminary studies were conducted to develop the assay methodology including tests of 1) growth media and seeding depth; 2) methods of weed control quantification); 3) methods and
concentrations for incorporation of rye tissue into the growth media, 4) testing of weed species for germination synchrony; and 5) testing of an irrigation system to uniformly water weed seed while preventing leaching of allelopathic compounds. This study confirmed that amounts of rye tissue:soil that approximated field conditions were suitable for the greenhouse assay system, that Redroot pigweed (Amaranthus retroflexus - dicot), and Large crabgrass (Digitaria sanguinalis - monocot) are capable of synchronous emergence and growth in the greenhouse, and that weed seedling emergence, weed biomass fresh weight, and image analysis of emerged biomass were useful methods of quantifying allelopathic activity in the lines to be screened. In late spring of 2007, the first of two greenhouse studies was conducted to evaluate the control of the 150 synthetic lines against the two weed species. Data from the greenhouse study was collected and is being analyzed statistically to determine the top
lines based upon this assay. Samples for GC analysis and lab bioassays have been ground and are being prepared for analysis of benzoxazilinone content in the phytotron grown tissue and field grown tissue is being quantified in the lab through gas chromatography. A system for production and extraction of etiolated rye seedlings was developed and large quantities of etiolated seedling biomass has been extracted in order to obtain pure standards of DIBOA and DIBOA-glycoside for GC analysis. This system incorporates the use of solvent extraction followed by preparative HPLC for isolation of pure compounds. In addition to the GC analyses, research underway includes an in vitro seed germination bioassay using extracts of field grown lines. Redroot pigweed seed will be germinated under constant light at 35C and large crabgrass will be germinated under constant light at 30C. Seed germination and measurement of radicle emergence will be recorded for the two weed test species. A second
greenhouse bioassay will be conducted beginning in September of 2007. Data from the combined bioassays and GC analyses will be used to select the rye lines to be used in subsequent breeding work.
Impacts
Weed control is frequently cited as one of the most significant obstacles to both conventional as well organic farming systems. The expanded use of a more allelopathic rye cover crop in agriculture would benefit a wide array of cropping systems. The use of rye as a winter cover crop yields the advantages of a thick mulch cover in the spring for weed suppression and provides the added benefit of improving soil holding capacity over the winter. Improved rye cover crops would also address the issue of herbicide resistance. Fewer herbicide applications would slow the evolution of resistance in weeds in addition to the substantial benefit of lower herbicide costs. Development of improved cover crops would also reduce the potential health risks from herbicide runoff and ground water contamination and minimize adverse environmental effects on non-target organisms including fish and wildlife.
Publications
- No publications reported this period
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