New Zealand Journal of Botany abstract

Received 12 July 1996; accepted 4 April 1997

Typical Frankia infect actinorhizal plants exotic to New Zealand

MICHAEL L. CLAWSON
DAVID R. BENSON
STEVEN C. RESCH

Department of Molecular and Cell Biology
U-44
University of Connecticut
Storrs, CT 06269-3044, USA

DAVID W. STEPHENS
WARWICK B. SILVESTER

Department of Biological Sciences
The University of Waikato
Private Bag 3105
Hamilton 2001, New Zealand

Abstract  Frankia strains are actinomycetes that fix N2 in root nodules of plants classified in eight families of the Angiospermae. The wide variety of plants infected has raised questions about the ecology and diversity of Frankia symbionts, and their co-evolution with actinorhizal plants. Partial sequencing was done of the small subunit (16S) rRNA gene from Frankia endophytes present in the root nodules of Alnus cordata, A. glutinosa, A. viridis, Casuarina equisetifolia, Coriaria arborea, C. plumosa, and Elaeagnus pungens growing in New Zealand. With the exceptions of the Coriaria spp., all of the plants are exotic to New Zealand. Analysis of the 16S rRNA gene indicates that the exotic species were nodulated by Frankia strains that cluster with strain groups previously shown to be typical for each actinorhizal host. Frankia in 12 native Coriaria spp. nodules yielded two sequences differing in only one position, suggesting a relatively low diversity compared with the exotic species.

Keywords  Frankia; actinorhizal; root nodule; nitrogen fixation; 16S rRNA; rDNA; Alnus; Coriaria; Elaeagnus; Casuarina

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