A comparison of two methods and different media for isolating Frankia from Casuarina root nodules

Four species of Casuarina were raised in the glasshouse and inoculated with nodules collected from nine different geographical areas within Australia. Isolations of Frankia were attempted from 10 of the Casuarina-Frankia nodule combinations using two methods, a nodule dissection and a filtration method. With both techniques Frankia isolates were obtained from four of the 10 Frankia sources. Spores were not observed in sections of nodules from the four sources from which Frankia was isolated, whereas spores were observed in the remaining six nodule sources. For selected nodule sources a range of isolation media were tried, but no improvement in the isolation success rate was achieved. The effect of host species on ease of isolation was studied. The results obtained suggested it was the Frankia strain and not the host plant species which determined the ease of isolation from Casuarina nodules.