VEGETOS: Eine internationale Zeitschrift für Pflanzenforschung

Deleterious Rhizosphere Microbes, Arbuscular Mycorrhizal Fungi and Quorum Management as Emerging Tools for the Biological Management of Weeds

Neeraj Malik and M U Charaya

Deleterious Rhizosphere Microbes, Arbuscular Mycorrhizal Fungi and Quorum Management as Emerging Tools for the Biological Management of Weeds

Crop losses ranging from 10% to 34% are reported to be caused by weeds. The cultural and mechanical methods for the management of weeds are temporary and quite expensive while chemical methods, though reasonably effective, are eco-unfriendly. Integrated weed management, with biological management at its core, undoubtedly holds key to sustainable check on the weeds in the future. In the past few decades, infection of weeds through weed pathogens has been mainly relied upon involving both classical and inundative strategies. Deleterious non-parasitic soil microbes, more frequent in the rhizosphere (deleterious rhizomicrobe, DRMs) have been found to be able to suppress weed growth substantially and, hence, hold considerable potential as biological weed control agents because of (i) their high root colonizing ability; (ii) their ability to produce specific toxins; and (iii) tolerance to antibiotics produced by other rhizospheric organisms. Weed management through DRMs is principally based on inundative strategy involving the application of deleterious microbes in high numbers to the soil, on vegetative residues, or in the spermosphere so that germination of weed seeds as well as vegetative growth and flowering of the weeds are inhibited leading to diminished competition pressure of weed against the crop. Positive results have been reported by many workers for managing velvetleaf, downy brome, green foxtail, and parthenium with bacteria (DRBs). Similarly, some deleterious rhizospheric fungi (DRFs) have also been found to suppress Convolvulus arvense, Orobanche cumana and Parthenium. When infected with mycorrhizal fungi, some crops exhibit better response as compared to weeds; thus, AMF inoculation also may tilt the balance in favour of crops confining the weeds to a tolerable level. By promoting Quorum-disruptive signals for PGPR and PGF; as also by promoting Quorum-supportive signals/substances for DRMs, it might be possible to facilitate biological management of weeds..