Diversity and Colonization of Putative Mycorrhizal Fungi in Eucalyptus Plantations in Southern China

Based on a recent survey of putative mycorrhizal fungus diversity and distribution in 15 Eucalyptus plantations located in the South China,17 species representing 10 genera were collected and identified likely to be ectomycorrhizal(ECM) fungi according to the presence of fruiting bodies under Eucalyptus stands. Fungi in the genera Scleroderma, Laccaaria and Pisolithus were the most common species associated with Eucalyptus. Further confirmation of fungal comparability and persistence for exotic euca-lypts is required as these fungi are commonly associated with native pine forests in southern China. There was a higher diversity of arbuscular mycorrhizal (AM)fungi than ECM fungi in eucalypt plantations. About 28 species(including 7 unnamed isolates)),belonging to four genera(Glomus, Acaulospora, Sclerocystis and Scutellospora)were observed in soil samples. Among them, 18 species were identified to be Glomus fungi making up 64% of the total taxa collected. G. formosanum and G. geosporum were gener-ally the most prevalent species in most plantations in the survey. G. mosseae,which was mainly restricted to alkaline soil in northern China,was also present in some soils from southern China. An additional survey on mycorrhizal colonization in roots of Eucalyptus over a range of plantation ages was undertaken from April to September. Roots from soil cores taken from 15 plantation sites were processed and examined under a microscope to assess mycorrhizal types and fungal colonization. Most root samples were associated with mycorrhizal fungi,either ECM or AM,or both. A general increase in root colonization with plant age by ectomycorrhizal fungi at the expense of AM fungal colonization indicated possible interaction between the two groups of fungi.