Submitted to: Journal of Chemical Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/28/1994
Publication Date: N/A
Interpretive Summary: Flavonoids are a group of compounds found throughout the plant kingdom. Many flavonoids have been shown to be involved in such processes as plant disease resistance, in the attraction of nitrogen-fixing bacteria, and in attracting pollinators. Peanut shells contain relatively large amounts of the flavonoid decomposition compound 5,7-dihydroxychromone (DHC). The role of DHC in the plant is poorly understood. DHC was found to inhibit the growth of two pathogenic fungi of peanut and the germination of several plant species at concentrations similar to those found naturally. DHC did not promote the growth of symbiotic nitrogen-fixing bacteria, although related compounds did significantly increase their growth rate. Breeding peanut varieties with increased DHC content may impart improved disease resistance and competitiveness with weeds.
Technical Abstract: 5,7-Dihydroxychromone (DHC), a flavonoid decomposition product that is present in peanut (Arachis hypogaea) shells was found to inhibit the radial growth of cultures of the soil pathogenic fungi Rhizoctonia solani and Sclerotium rolfsii with ED50 values of 18 and 26 uM, and radicle elongation of velvetleaf, corn, peanut and wheat with ED50 values of 30, 50, 65 and 200 uM, respectively. DHC had no effect on the growth of Bradyrhizobium sp. at 10 uM/in medium containing low (1.0 g/L) mannitol as the carbon source although the related flavones luteolin and chrysin each promoted bacterial growth at 10 uM 48 after inoculation. When added to high (10.0 g/L) mannitol medium DHC initially inhibited growth, but by 120 h after inoculation the growth of all treatments were similar. These results suggest a role for DHC released from peanut shells in suppressing pathogenic fungal infection and competing plant growth but not for Bradyrhizobium growth promotion.