Submitted to: Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: March 15, 2007
Publication Date: N/A
Technical Abstract: Effective, affordable weed control is a challenge to sustainable rice production in the U.S. Research efforts in Arkansas have identified several rice lines that can suppress economically important C4 grass weeds such as Echinochloa crus-galli and Leptochloa fusca ssp. fascicularis. Earlier findings suggested that the suppression mechanisms may include competition as well as allelopathic components. These suppressive rice lines often caused a greater reduction of weed root biomass (measured by 13C depletion) as well as aboveground plant growth. An ongoing breeding/selection program has been underway for several years to combine the desirable quality (often lacking in suppressive rice lines) and yield characteristics of commercial southern long grain rice with high-yielding, suppressive rice lines. One such selection from the cross PI 338046 / KATY // PI 312777, which produced excellent yield, commercially acceptable quality, and modestly improved weed suppression, was advanced (as RU0701087) into the Uniform Regional Rice Nursery in 2007. However, lack of suppressive capability that is adequate for weed control continues to be a key limitation for these kinds of selections. Alternative rice germplasm that could correct this common limitation may be found in the form of high yielding, disease-resistant indica lines from China (e.g. derivatives of ‘4484’ (PI 615022)) and commercially available hybrids which have demonstrated the greatest weed suppressive capability of all rice lines we have tested. These also are being evaluated in performance trials in five states of the southern U.S. where their yields, quality, and disease resistance compare favorably with existing commercial standards. However these tests utilize standard herbicides for weed control and do not include an evaluation of weed suppression. Because year-to-year variations in the environment and weed pressure are likely to remain high and unpredictable, even the most weed suppressive rice varieties are likely to require the stabilizing effect of additional weed control measures (e.g. reduced rates of supplemental herbicide). Under these circumstances, weed suppressive rice varieties could be a key component of productive, affordable, and profitable U.S. rice systems in the future.