Survey of fungi and nematodes associated with root and stolon diseases of white clover in the subtropical dairy region of Australia

Abstract

A survey of 12 white clover-based dairy pastures on the north coast of New South Wales and south-eastern Queensland, Australia, detected 65 species of fungi and 6 nematode species. The fungi included species of Fusarium, Gliocladium, Codinaea, Alternaria, Colletotrichum, Drechslera, Rhizoctonia, Phoma, Pythium, Phytophthora, Penicillium, Rhizopus and Trichoderma from roots and stolons of white clover. Fungal rots of roots and stolons were most severe during the summer months (November and January samples), while root-knot symptoms caused by plant parasitic nematodes were more severe in June. Sedentary endoparasitic nematodes Meloidogyne trifoliophila, Heterodera trifolii and the ectoparasitic nematode Helicotylenchus dihystera were the numerically dominant nematodes in the region. Other nematode species, including Pratylenchus, Xiphinema and Tylenchorhynchus, were present at lower frequencies and principal component analysis indicated that these were less important as white clover pathogens. Meloidogyne trifoliophila was detected for the first time in Australia and was present at all sites. Many of the fungi and nematodes found are common pathogens of white clover. These pathogens are likely to be contributing to the poor seedling performance, growth and persistence of white clover typical in dairy pastures of the subtropical east coast of Australia.