Effect of the clover root-knot nematode (Meloidogyne trifoliophila) on growth of white clover

Root-infecting nematodes are common on white clover (Trifolium repens) in dairy pastures on the north coast of New South Wales and southeastern Queensland. Australia, where they are thought to contribute to poor growth and persistence. The nematode responsible for causing root-knot symptoms on white clover was identified as Meloidogyne trifoliophila. a species not previously recorded from Australia. M. trifoliophila failed to reproduce on any of the standard North Carolina hosts used to identify M. javanica. M. hapla, M. arenaria and M. incognita. but caused severe galling and exhibited a high rate of reproduction on white clover. PCR primers for these Meloidogyne species also failed to amplify DNA of M. trifoliophila. Identity was confirmed by morphological measurements and plant symptoms. In a glasshouse test, increasing initial nematode density within the range 0 to 10 000 per 500 ml pot led to reduced shoot and root growth, fewer nodules and more severe root-knot symptoms. A second pot test screened weed species as potential alternative hosts of M. trifoliophila. None of the eight grass species was galled but M. trifoliophila reproduced on two of the eight dicotyledon weeds, spear thistle (Cirsium vulgare) and pigweed (Portulaca oleraceae).