|Moldenhauer, Karen a.k.|
Submitted to: Weed Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 8/30/2011
Publication Date: 1/1/2012
Publication URL: handle.nal.usda.gov/10113/54992
Citation: Gealy, D.R., Moldenhauer, K. 2012. Use of 13C isotope discrimination analysis to quantify distribution of barnyardgrass and rice roots in a four-year study of weed-suppressive rice. Weed Science. 60:133–142. Interpretive Summary: Weeds are a constant and costly pest in rice worldwide. Distribution and competitive interactions of rice and weed roots may be important for the natural weed suppression activity found in rice varieties, but measurements of intertwined rice and weed roots in field environments is difficult. A stable carbon isotope (13C) discrimination method was used to detect levels of barnyardgrass and rice roots in soil in a four-year study. Rice roots usually dominated the below-ground environment, even in weed-infested plots. An indica variety of tropical origin (PI 312777) was more effective at suppressing the weed and had higher yields than commercial rice varieties, and its roots tended to thrive in the soil area between rows near the ground surface. Field performance and weed suppression of rice lines that were developed by crossing suppressive indica and commercial rice varieties were usually at an intermediate level between the two parental types. The findings suggest that root interactions contribute to the weed-suppressive activity of indica rice varieties, and that a better understanding of rooting traits may be useful in the development of improved weed-suppressive rice varieties.
Technical Abstract: A four-year field study was conducted to evaluate weed control potential of weed-suppressive indica rice cultivars, common commercial cultivars, and crosses between the two types. Under diverse field environments, indica cultivars produced relatively high and consistent yields and levels of weed suppression against barnyardgrass. 13C analysis revealed that under weed pressure, rice roots dominated the below-ground environment. This was particularly true for PI 312777 roots between rows near the soil surface, suggesting that root architecture and interference may be important components of its weed-suppressive activity in a flooded field environment. Performance of two ‘intermediate’ indica/tropical japonica crosses were only modestly more suppressive than most of the ‘non-suppressive’ commercial cultivars evaluated. Our findings suggest that root interference may contribute to the effectiveness of weed-suppressive indica rice cultivars, and that a better understanding of rooting traits may be useful in the development of improved weed-suppressive rice varieties.