Submitted to: Book Chapter
Publication Type: Book / chapter
Publication Acceptance Date: 12/10/2003
Publication Date: 10/1/2005
Citation: Gealy, D.R., Moldenhauer, K.A. 2005. Developing weed suppressive rice cultivars for the southern U.S.: strategies, progress, and challenges. In: Singh, H., Batish, D., Kohli, R., editors. Handbook of Sustainable Weed Management. Binghamton, New York:Haworth Press. p. 257-296. Interpretive Summary: This is a book chapter, interpretive summary not required.
Technical Abstract: For thousands of years, rice has been among the most important crop species. Currently, it is the main food source for more than half of the earth's population. The U.S. is one of the leading exporters of rice in the world. However, weeds can severely limit the quality and quantity of rice produced, even when growers use modern chemical and cultural methods to control them. Barnyardgrass and its relatives are the most predominant weeds in rice throughout the U.S. Red rice is the worst weed in the South where more than 80% of U.S. rice is produced. The desire to reduce herbicide use and costs of production has prompted increased interest in development of weed-suppressive rice cultivars in recent years. In Arkansas field tests, numerous rice lines from the U.S. world collection have provided high levels of suppression against aquatic weeds such as ducksalad and redstem when compared to commercial cultivars. A number of rice lines have suppressed barnyardgrass, however, red rice has not been effectively suppressed because of its aggressive growth characteristics. Weed suppression often results from advantageous rice plant architecture and vigor mechanisms that deny resources to weeds. In some cases, phytotoxic allelochemical exudates appear to contribute to weed suppression. Natural suppression systems typically perform best when weeds are controlled early in the season. Foreign indica cultivars have produced higher yields, greater barnyardgrass suppression, and greater economic returns than U.S. cultivars at reduced herbicide rates. However, these cultivars produce an inferior plant type and grain quality. Traditional cross breeding, mutation breeding, and modern molecular genetics when combined with appropriate screening techniques may lead to improvements in the commercial quality and weed suppression characteristics of these promising rice lines. If successful, such efforts may result in highly competitive rice cultivars that supplement the control of weeds.