Improvement of Allelopathy in Crops for Weed Management

Abstract

Weeds are a major concern in all agricultural systems around the world. In contrast to the progress observed with respect to disease resistance, few attempts have been made to breed crops to be competitive against weeds. This is partly due to the success of herbicides as an effective solution against weeds. The apparent complex nature of competitive ability in crops and the widespread impression that competitive ability is negatively correlated with yield is another reason weed suppressive crops have not been selected for. However, recent research with rice shows that it is possible to increase competitive ability without affecting yielding ability (Jones et al., 1997; Olofsdotter et al., 1999). By increasing our understanding of plant competitive ability, we may potentially improve a crop’s competitive ability, the key to successful breeding of weed-fighting cultivars (Mortimer et al., 1999). Theoretically, enhanced crop production, independent of weed growth, can be obtained in three different ways: (i) growing plants that will yield well in spite of weed infestations (weed tolerant crops or cultivars), (ii) growing plants that suppress the surrounding flora (weed-suppressing crops or cultivars) (Lemerle et al., 2001) or (iii) both strategies used at the same time. For long-term weed reduction, greater benefits exist with the later strategy of selecting for weed suppression and thereby increasing competitive ability. Increased crop competitive ability, will suppress weed impair their regenerative capacity, thus decreasing weed abundance in the field over time.