Characterisation of Eucalyptus rhizospheric communities using fatty acid methyl ester (FAME) profile analysis

Abstract

Hybrid vigour is exploited in Eucalyptus forestry through the production of interspecific hybrids. Hybrids are deployed via cuttings that often suffer from poor rooting. Rhizospheric microorganisms have been associated with rooting enhancement, therefore knowledge of the diversity of microorganism communities, and their abundance and changes over time could be of value in commercial forestry. This knowledge could be applied when sourcing and formulating combinations of useful rhizospheric microorganisms for the treatment of Eucalyptus hybrid cutting genotypes, specifically to improve rooting in the nursery for the establishment of clonal forests. Fatty acid methyl ester (FAME) profiles were prepared for 3-month-old and 5-year-old soil samples collected from rhizospheres of Eucalyptus grandis × Eucalyptus nitens clones to characterise microbial diversity. Saturated, monounsaturated and polyunsaturated fatty acids were present in both soil age groups, although in different proportions. Proportions of saturated fatty acids in the younger samples were greater than in the older samples, while proportions of unsaturated fatty acids were fewer in the younger samples. Palmitic (C16:0) and stearic (C18:0) acids were the most prevalent. Both Shannon’s and Simpson’s indices confirmed that younger soils were more diverse. The greater proportion of polyunsaturated fatty acids in older samples, especially linoleic, α-linolenic and γ-linolenic acids, suggests increasing establishment of fungi.