Allelopathic Root Leachate Effects of Lolium multiflorum x L. perenne on Crops and the Concomitant Changes in Metabolic Potential of the Soil Microbial Community as Indicated by the Biolog Ecoplate™

Plant roots serve a multitude of functions including anchorage, provision of nutrients and water, as well as production of exudates with growth regulatory properties. Some root exudate components may act as allelochemicals and mediate interactions between plants and other organisms in the rhizosphere. The significance of micro-organisms in influencing allelopathic activity is largely not investigated in bioassays for allelopathy. The aim of this study was to test the appropriateness of Biolog EcoPlatesTM as a quick and relatively cheap method of establishing the presence of microbe interactions mediated by allelopathic pot leachates from either rotational crops or L. multiflorum x L. perenne. In this green house study, Biolog EcoPlatesTM were used to indicate the effect of pot leachates from six different donor plants on the soil microbial populations associated with the same species serving as acceptor plants, grown in pots with soil from the same origin in both sets of pots. Pot leachates from donor plants were added to the acceptor plants on a weekly basis until plants reached maturity. Soil samples from acceptor pots were used to inoculate Biolog EcoPlatesTM and the carbon utilisation patterns were compared to the pattern obtained for the soil microbial populations before treatment commenced. Findings indicate that root exudates can influence the microbial community structure in the rhizosphere and location is an important factor governing plant-plant and plant-microbe interactions. The Biolog EcoPlate™ could be used as an indicator of the allelopathic activity of crop or weed species.