Submitted to: Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: May 9, 2008
Publication Date: September 21, 2008
Citation: Gealy, D.R., Moldenhauer, K.K., Mattice, J., Yan, W. 2008. Developments in rice allelopathy: Searching for the balance between allelopathic activity, agronomic viability and commercial acceptability. Proceedings of the 5th World Congress on Allelopathy, Saratoga Springs, NY, Sept. 21-25, 2008. p. 56. Technical Abstract: Sustainable weed control is an ongoing challenge in rice production. Indica rice lines that suppress troublesome C4 grass weeds such as Echinochloa crus-galli and Leptochloa fusca ssp. fascicularis have been evaluated extensively in Arkansas. Earlier findings suggested that suppression likely included both competition and allelopathic components. These indicas often reduced growth of weed roots and aboveground parts more than did commercial cultivars. In an ongoing breeding/selection program we attempt to combine desirable quality and yield characteristics of southern long grain cultivars with highly weed-suppressive rice lines. One such selection (RU0701087; from pedigree PI 338046 / KATY // PI 312777) was evaluated in the five-state Uniform Regional Rice Nursery (URRN) in 2007. In this test, its yield and quality were acceptable, but in other tests, weed suppression was less than that of the PI 338046 and PI 312777 parents. Additional selections that suppressed E. crus-galli in bioassays were not effective in the field. Chinese indicas such as ‘4484’ (PI 615022) and its irradiated mutant selection, ‘4484-1693’ (RU0603075), also have been evaluated in field tests including the URRN. Typically, weed suppression by these indica lines was greater than that of commercial standards, and yield and disease tolerance were as high or higher than the standards. Commercial, high-tillering hybrids have also suppressed weeds effectively in the field. High-yielding indica lines such as 4484-1693 are now being used in limited commercial production of organic rice, in part because of their weed-suppressive characteristics. A challenge for reduced-input systems is that environmental conditions and weed pressure vary from year-to-year. Thus, weed-suppressive rice cultivars in systems permitting herbicides (i.e. not organic) could benefit substantially from herbicide application at reduced rates or on a ‘wait-and-see’ basis. Using such an approach, weed suppressive cultivars could be a viable component of major U.S. rice systems.