Growth and nodulation of provenances of Casuarina cunninghamiana inoculated with a range of Frankia sources

Abstract

Seed and root nodules (for use as a Frankia inoculum) collected from 18 provenances of Casuarina cunninghamiana Miq. were used in a complete cross-inoculation experiment conducted in a glasshouse. The provenances covered the geographical range of the species and represented major river systems. They were arranged a priori into five groups according to geographical location. Seventeen of the inocula were effective on seed from all provenances; one inoculum failed to nodulate seedlings from any provenance. Inoculum source, seed source and their interaction all affected plant growth. Greatest shoot weight was obtained with seed and inoculum combinations from similar geographical regions, particularly northern inocula with northern seed sources and southern inocula with southern seed sources. When averaged over all seed sources northern inocula were the most generally effective in promoting plant growth. In contrast, when averaged over all inoculum sources, southern seed sources grew best. These results demonstrate the potential for improving the effectiveness of the C. cunninghamiana-Frankia association in forestry by selection of the symbiotic partners.