Factors associated with the suppressiveness of sugarcane soils to plant-parasitic nematodes.

摘要: Observations in three Australian sugarcane fields suggested that the soil just under trash blanket (the covering of crop residue remains on surface after crops are harvested) was suppressive to plant-parasitic nematodes. Roots were concentrated this upper layer but nematode populations relatively low and roots showed few signs damage. Root biomass much lower 15 cm further down profile, where root health poor nematodes 3-5 times higher than near surface. A bioassay which Radopholus similis (a does not occur soils) inoculated into heat-sterilized untreated soils, confirmed biological factors limiting some with from 0-2 more 15-17 cm. Surface one site highly suppressive, as only 16% R. recoverable heated retrieved 8 days. Numerous chemical, biochemical, properties measured, non-linear regression analysis identified two major groups significantly associated suppressiveness. One group reflected amount organic matter (total C, total N, labile C) other size free-living community numbers nematodes, plant associates, bacterial feeders, fungal carnivores). These results suppressiveness biologically mediated sustained by C inputs residues roots. Since nematode-trapping fungi test soils could be quantified using traditional dilution plating methods, their possible role agents assessed generating TRFLP profiles Orbiliales-specific primers, sequencing cloned PCR products. Although molecular data obtained a limited number samples, level suppression correlated Orbiliales clone also related species TRFs, suggesting may have been operating soils.