|Ogg, Jr, Alex - RETIRED, USDA-ARS|
Submitted to: Weed Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 9, 1998
Publication Date: N/A
Interpretive Summary: Jointed goatgrass is a serious pest in winter wheat in the west because there are no herbicides to control it without damaging the wheat crop. One suggested strategy to manage jointed goatgrass involves breeding more competitive wheat cultivars which will be able to yield well when growing with jointed goatgrass, and at the same time, reduce the seed production of jointed goatgrass. The problem is that no one has determined what should be bred into wheat to make it more competitive against jointed goatgrass. The purpose of this research was to determine what traits in winter wheat are important to increasing the competitiveness of winter wheat against jointed goatgrass. We determined that in a dry environment the rate at which a wheat plant gained height was most important in making it competitive. The faster the wheat gained height, the better it yielded and the worse the jointed goatgrass grew. It was not important how tall the wheat eventually grew, it was only important that it grew fast early in the growing season. In a wet year, height growth was not as important as how many wheat heads the plant produced and how fast the wheat gained weight. Also, wheats which could use lots of soil moisture did very well. Overall, winter wheat was more competitive in wet years than in dry years. Our findings will allow breeders to select for more competitive winter wheats in the Pacific Northwest in both dry and wet environments. Simple height measurements, early in the spring, will allow breeders to select for new winter wheat varieties that will be more competitive when growing with jointed goatgrass and perhaps other weed pests.
Technical Abstract: It is generally accepted that planting a more competitive crop will reduce yield losses due to weeds and perhaps reduce the production of weed seeds. The traits that make a crop cultivar competitive are not known, which makes the selection for competitive cultivars more difficult. The objectives of this study were to determine which traits in winter wheat were important in enhancing winter wheat competitiveness against jointed goatgrass. Jointed goatgrass is an important winter annual grass weed which cannot be controlled selectively in winter wheat. Seven cultivars of soft white winter wheat were grown with and without competition from jointed goatgrass over two growing seasons. Measurements of numerous traits of winter wheat and jointed goatgrass were taken throughout each growing season. The data were analyzed using path analysis with latent variables to determine which traits most enhanced competitiveness. In a drier year, increased rate of height development was important in maintaining wheat yields when wheat was growing in competition with jointed goatgrass. Increased rate of height development also was an important trait in reducing jointed goatgrass seed production. In a wet year compared to a dry year, the number of wheat heads per plant, the rate of water use, and weight gain, were positively correlated to maintaining winter wheat yields. Jointed goatgrass seed production in the wet year was reduced overall compared to the dry year, but from the cultivars tested, there were no traits identified which were critical in enhancing this loss of seed production. This study suggests that wheats which have greater height development rates will be more competitive when growing in fields infested with jointed goatgrass.