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 d airy pastures on the north coast of New South Wales and southeastern Queens land. Australia, where they are thought to contribute to poor growth and pe rsistence. The nematode responsible for causing root-knot symptoms on white clover was identified as Meloidogyne trifoliophila. a species not previous ly 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 sp ecies also failed to amplify DNA of M. trifoliophila. Identity was confirme d by morphological measurements and plant symptoms. In a glasshouse test, i ncreasing 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 roo t-knot symptoms. A second pot test screened weed species as potential alter native hosts of M. trifoliophila. None of the eight grass species was galle d but M. trifoliophila reproduced on two of the eight dicotyledon weeds, sp ear thistle (Cirsium vulgare) and pigweed (Portulaca oleraceae).