Characterisation of root-nodule bacteria isolated from perennial Southern African species of Lotononis
Ardley, J.K., Yates, R.J., Howieson, J.G., Nandasena, K.G., O'Hara, G.W. and Tiwari, R.P. (2005) Characterisation of root-nodule bacteria isolated from perennial Southern African species of Lotononis. In: 14th Australian nitrogen fixation conference, 21 - 25 November, Katoomba, Australia.
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Lotononis is a genus of approximately 150 shrubs, herbaceous perennials and annuals belonging to the subfamily Fabaceae (Van Wyk, 1991). They are distributed mainly in southern Africa, with some species extending throughout Africa, southern Spain, Turkey, south-eastern Bulgaria and part of the Arabian Peninsula to the north-west of the Indian sub-continent (Van Wyk, 1991). Lotononis species have shown potential as perennial pasture legumes that can be used to help reduce the risk of dryland salinity in southern Australian agricultural systems. Species in the section Listia in particular may be useful as pasture legumes as they are perennial, stoloniferous, and lack the poisonous cyanogenic or alkaloid compounds found in some species of Lotononis. L. bainesii, from the Listia section, has been shown to grow well in southern Australia (Roberts & Carbon, 1969) and will grow on acid, sandy soils (R. Yates, pers. comm.).
L. bainesii is nodulated by pink-pigmented root-nodule bacteria. Jaftha et al. (2002) characterised nine L. bainesii isolates and found them to be related to Methylobacterium. The genus Methylobacterium, often referred to as pink-pigmented facultative methylotrophs (PPFMs), are capable of growth on C1 compounds such as formate and methanol as sole carbon sources. PPFMs are ubiquitous in the plant phyllosphere and rhizosphere, where they utilize methanol and other C1 compounds that are the products of plant metabolism (Trotsenko et al, 2001). They can promote the germination or the growth of plants, probably because of their ability to synthesise auxins, cytokinins and other plant growth promoting substances (Holland & Polacco, 1994; Ivanova et al., 2000; Trotsenko et al., 2001). However, until the paper by Sy et al. (2001), describing Methylobacterium nodulans, which was isolated from nodules of Crotalaria species found in Senegal, no Methylobacterium species had been known to nodulate legumes, or indeed to fix nitrogen.
The objectives in this study were to characterise root-nodule bacteria isolated from four species from the Listia section of Lotononis (L. angolensis, L. bainesii, L. listii and L. solitudinis) using a range of phenotypic and genetic techniques.
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|Murdoch Affiliation:||Centre for Rhizobium Studies|
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