Influence of Herbicides on the Competitive Ability of Fungi to Colonize Plant Tissues

Abstract

SUMMARYExperiments show that the presence of herbicide residues in plant remains may be a potent factor determining the outcome of competition between saprophytic fungi colonizing such substrates. Pairs of fungi were induced to compete with each other for a substrate both in the presence and in the absence of herbicides. In all cases the outcome of competition for a substrate incorporating the herbicide was different from that for the substrate alone. Paraquat sprayed on to potato haulm altered the outcome of competition between Trichoderma viride and Fusarium culmorum in favour of F. culmorum and the same herbicide on wheat chaff suppressed Rhizopus stolonifer in favour of Aspergillus niger. Treatment of leaves of Raphanus raphanistrum with MCPA altered the outcome of competition between Fenicillium notatum and Aspergillus niger in favour of A. niger.

Mechanism of biodegradation of paraquat by Lipomyces starkeyi

“…Several microorganisms have been reported as being capable of the in vitro degradation of paraquat (2,4,8,12,25,30). In the majority of the cases, however, paraquat degradation was shown to be extremely variable in both extent and rate, and evidence of only one degradation product other than CO2 has been reported, the N-methyl betaine of isonicotinic acid (8).…”

<i>In vitro</i> Evaluation of Growth Inhibition of Some Common Soil Fungi by Selective and Non-selective Herbicides

“…A change in the patterns of colonization of substrates by microorganisms may affect the rate at which these substrates are subsequently decomposed [20].…”

Effects of Constituents of Gramoxone W on Rates of Respiration of Soil Fungi

“…Gramoxone W (Registered Trade Mark of Plant Protection Limited), a commercial formulation of paraquat dichloride (l,r-dimethyl-4,4'-bipyridylium dichloride), has marked inhibitory effects on the growth of some soil fungi, but not on others (Wilkinson & Lucas, 1969a, b). Its presence in moribund plant tissues may, therefore, be an important factor in determining the fungal species capable of colonizing such tissues (Wilkinson & Lucas, 1969c). However, it is not known if the effects are due to paraquat dichloride or to additives present in the commercial formulation.…”