Breeding Wheat for Increased Weed-Suppressive Ability against Italian Ryegrass

Breeding Wheat for Increased Weed-Suppressive Ability against Italian Ryegrass

Summary

Research was conducted to determine the relative contribution of allelopathy and competitive to the weed suppressive ability of winter wheat cultivars in North Carolina.

Fifty-eight winter wheat lines adapted to the southeastern United States were screened for allelopathic activity against Italian ryegrass (Lolium perenne L. ssp. multiflorum (Lam.) Husnot) in an agar based seedling bioassay. Eight strongly and weakly allelopathic lines were then chosen for evaluation for weed suppressive ability and grain yield tolerance in a replicated field experiment. Significant genotypic differences in weed suppressive ability were found. Although the allelopathic activity of genotypes varied in the seedling bioassay, no correlations between allelopathy and weed suppressive ability or grain yield tolerance were observed. Weed suppressive ability was correlated with competitive traits including vigor and erect growth habit during tillering (Zadoks GS 29), high leaf area index (LAI) at stem extension (GS 31), plant height at tillering and stem extension (GS 29, 31), grain yield in weedy conditions, and grain yield tolerance. Therefore preliminary results suggest that breeders in the southeastern United States should focus their efforts on improving competitive traits within adapted germplasm rather than selecting for high allelopathic activity in order to achieve maximum gains in weed suppressive ability.

A parallel study was conducted to assess the range of weed suppressive ability against Italian ryegrass (Lolium perenne L.ssp. multiflorum (Lam.) Husnot) existing in winter wheat lines adapted to North Carolina growing conditions and to identify wheat morphological traits and molecular markers that could facilitate indirect selection for weed suppression in the southeastern United States. Fifty-three commercially available cultivars and advanced experimental lines were over-seeded with a uniform, high rate of Italian ryegrass, evaluated for various morphological traits throughout the growing season, and investigated for weed suppressive ability. Genotypic differences in end of season Italian ryegrass seed head density (P < 0.05) were detected among the tested wheat lines. Reduced Italian ryegrass seed head density was correlated (P < 0.05) with high vigor during tillering (Zadoks GS 25, 29) and heading (GS 55), erect growth habit (GS 29), low NDVI (GS 29), high LAI at stem extension (GS 31), early heading date, tall height throughout the growing season (GS 29, 31, 55, 70-80).

Objectives/Performance Targets

Research was conducted to determine the relative contribution of allelopathy and competitive to the weed suppressive ability of winter wheat cultivars in North Carolina. Fifty-eight winter wheat lines adapted to the southeastern United States were screened for allelopathic activity against Italian ryegrass (Lolium perenne L. ssp. multiflorum (Lam.) Husnot) in an agar based seedling bioassay. Eight strongly and weakly allelopathic lines were then chosen for evaluation for weed suppressive ability and grain yield tolerance in a replicated field experiment. A parallel study was conducted to assess the range of weed suppressive ability against Italian ryegrass existing in winter wheat lines adapted to North Carolina growing conditions and to identify wheat morphological traits and molecular markers that could facilitate indirect selection for weed suppression in the southeastern United States.

Accomplishments/Milestones

This year we published two peer reviewed manuscripts describing research on weed suppressive ability in wheat, completed the allelopathy screening bioassay, and conducted the first year of two parallel field experiments on weed suppressive ability. 

Published Manuscripts:

• • Worthington, M. and S.C. Reberg-Horton. 2013. Breeding Cereal Crops for Enhanced Weed Suppression: Optimizing Allelopathy and Competitive Ability. Journal of Chemical Ecology. 39: 213-231. doi:10.1007/s10886-013-0247-6

• • Worthington, M., S.C. Reberg-Horton, D. Jordan, and J.P. Murphy. 2013. A Comparison of Methods for Evaluating the Suppressive Ability of Winter Wheat Cultivars against Italian Ryegrass (Lolium perenne). Weed Science. 61: 491-499. doi:10.1614/WS-D-12-00167.1

Impacts and Contributions/Outcomes

This year we published two peer-reviewed manuscripts related to the project and presented our results at numerous conferences and field days.  In addition, I attended the student organic seed symposium in Washington and shared results with other graduate students working on breeding for organic systems.  Paul Murphy and I also took other public sector breeders from across the Southeast to see our experimental plots and learn about selection for weed suppressive ability

Extension Posters and Presentations:

• • Breeding winter wheat for increased weed suppressive ability against Italian ryegrass. Worthington M., C. Reberg-Horton, D. Jordan, and P. Murphy. Oral presentation at the 2013 Annual Meetings of the Crop Science Society of America.

• • Breeding winter wheat for increased weed suppressive ability against Italian ryegrass. Worthington M., C. Reberg-Horton, D. Jordan, and P. Murphy. Poster at the 2013 North Carolina State University Center for Environmental Farming Systems Organic Grain Field Day.

• • Breeding winter wheat for increased weed suppressive ability against Italian ryegrass. Worthington M., C. Reberg-Horton, G. Brown-Guedira, D. Jordan, and P. Murphy. Oral presentation at the 2013 joint meeting of the Eastern Wheat Workers, Southern Small Grains Workers, and Great Lakes Wheat Workers.

• • Breeding winter wheat for increased suppressive ability against Italian ryegrass. Worthington M., C. Reberg-Horton, D. Jordan, and P. Murphy. Poster at the 2012 Annual Meetings of the Crop Science Society of America.

• • Breeding winter wheat for increased suppressive ability against Italian ryegrass. Worthington M., C. Reberg-Horton, D. Jordan, and P. Murphy. Poster at the 2012 Annual Meeting of the National Association of Plant Breeders.

Collaborators: