Submitted to: Rice Technical Working Group Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: January 1, 2006
Publication Date: February 15, 2006
Citation: Gealy, D.R., Black, H.L., Moldenhauer, K.K., Yan, W., Rutger, J.N. 2006. Promising weed suppressive activity in high-yielding indica rice and hybrid rice. Rice Technical Working Group Meeting Proceedings, February 29-March 1, 2006, Houston, Texas. 2006 CSROM. Technical Abstract: Effective weed control in U.S. rice has relied primarily on herbicides since the 1960s. Several indica rice lines tested in the 1980s suppressed aquatic weeds. Since then, they and their crosses with standard U.S. cultivars, and other indica lines were found to suppress barnyardgrass (Echinochloa crus-galli) better than standard U.S. cultivars. In 2005 several weed-suppressive standards (eg PI 312777) and U.S. cultivars were compared to several high-yielding Asian indica lines (some of which had been mutated to improve plant/grain quality), commercial hybrids, and crosses between weed-suppressive standards and U.S. cultivars. Field studies were conducted at the University of Arkansas Rice Research and Extension Center near Stuttgart, AR. All rice lines were drill-seeded at a rate of 430 seeds/m2. Plots were sprayed postemergence with 1.1 kg/ha propanil, one fourth of the standard use rate, to partially suppress weeds. Plant height, days to heading, tiller production, grain yield, and visual control of barnyardgrass were among the characteristics evaluated. Weed suppression activity in 2005 was generally lower than that observed in previous years, probably due to an unusually dry extended period during the planting season that was followed by an unusually rainy/cloudy period early in the growing season. However, previously documented general trends among cultivars were observed. In one study, control ratings for CL XL8 (imidazolinone-resistant hybrid), 4612 (indica line from China), Drew, and several crosses between weed-suppressive standards and U.S. cultivars were as high as those from the weed-suppressive standards PI 312777 and PI 338046 (control >= 54%). Commercial cultivars such as Ahrent, L205, M205, and Lemont provided less control (35-40%). In a second study, CL XL8, STG96L-26-093 (PI 338046/Katy cross), and Drew provided as much control as PI 312777 (weed control >= 54%), whereas Ahrent and Lemont provided 38 and 30% control, respectively. In a third study, Chinese indica lines R312, 4593, and 4612, mutated Chinese indica lines Shufeng 121-1655 and 4484-1665, and commercial hybrids CL XL8 and XP723 provided control comparable to PI 312777 (>= 51%). Ahrent and Kaybonnet were among those entries providing less than 40% control. Several of the mutated indica lines may be promising as parental lines or cultivars with commercially acceptable, high yielding, high quality, weed-suppressive traits.