Publications (3)2.32 Total impact
Article: Effects of a plant parasitic nematode (Heterodera trifolii) on clover roots and soil microbial communities[show abstract] [hide abstract]
ABSTRACT: We studied the effects of the root endoparasitic nematode Heterodera trifolii on rhizodeposition and the root architecture of white clover (Trifolium repens). Rhizosphere solutions were collected from the root systems of plants growing with and without H. trifolii (200 juveniles per inoculated plant) in sand-based microlysimeters. The organic carbon (C) content of these solutions was analyzed, and they were applied to plant-free soils to investigate microbial responses. Although plant biomass was unaffected by nematodes, the architecture of the root systems was significantly altered, with a decrease in overall root length and an increase in the density of lateral branches from the primary root. The presence of nematodes reduced the concentration of organic compounds in the rhizosphere solutions but only on the final sampling date (75days). Analysis of microbial signature phospholipid fatty acids revealed no change in the structure of the microbial communities in soils to which rhizosphere solutions were applied. However, these microorganisms did respond with changes in substrate utilization patterns (community-level physiological profiles). Microbes in soils that received rhizosphere solutions from the nematode-infected clover showed lower utilization of most substrates but higher utilization of oligosugars. These responses appear to be related to changes in roots and rhizodeposition associated with nematode infection of clover roots. The results of this study suggest that root herbivory can negatively impact carbon-limited soil microbial communities via changes in root architecture that moderate rhizodeposition.Biology and Fertility of Soils 04/2012; 43(5):541-548. · 2.32 Impact Factor
Article: Isoflavonoid Conjugate Accumulation in the Roots of Lucerne (Medicago Sativa) Seedlings Following Infection By the Stem Nematode (Ditylenchus Dipsaci)[show abstract] [hide abstract]
ABSTRACT: Susceptible (cv. Sabilt) and resistant (cv. Vertus) lucerne (Medicago sativa) seedlings were infected with the stem nematode, Ditylenchus dipsaci and foliar and root tissue analysed for the presence of isoflavonoids. Within 10 days of inoculation, clear differences were seen in the responses of resistant and susceptible plants. Neither cultivar accumulated detectable concentrations of isoflavonoids or their metabolites in the foliar tissue, where all the nematodes were localized; in the roots of infected Vertus plants, the malonyl glucosides of medicarpin and formononetin and the glucosides of coumestrol and formononetin were present at two to three times the concentrations in the uninfected controls. In susceptible Sabilt, these changes were less marked and were restricted to a transient increase in the glucosides of formononetin and coumestrol. Increases in these isoflavonoid conjugates in the roots were associated with increased activities of the enzyme phenylalanine ammonia lyase, but the enzyme was not induced in infected shoots. The results suggest that although increases in isoflavonoid conjugates in the roots were not directly responsible for resistance to D. dipsaci, their accumulation was in response to a systemic signal from the infected shoots, and was correlated with resistance.Nematologica. 12/1994; 41(1-5):51-66.
Article: Rhizodeposition and soil microbial communities in clover plants infected with the clover cyst nematode, Heterodera trifolii