SPECIFICITY AND EFFECTIVITY IN NODULATION BY FRANKIA ON SOUTHERN-HEMISPHERE ACTINORHIZA

Nodulation ability was tested for Frankia strains HFPCcI3 and EL1, and Frankia sources A.t. and G.a. from Allocasuarina torulosa and Gymnost oma australianum, respectively, on A. torulosa Mig., Casuarina cunning hamiana Mig., G. australianum L. Johnson and Elaeagnus triflora Roxb. It was shown that A. torulosa and C. cunninghamiana formed nodules onl y with the Frankia sources obtained from their own host plant, while E . triflora formed nodules with three of the four Frankia sources teste d. All nodules formed were effectively fixing nitrogen. Specific nitro genase activity was highest in E. triflora inoculated with the Frankia strain isolated from nodules of the same species. Identification of F rankia sources in the nodules was performed by use of PCR amplificatio n of DNA with a random primer. PCR amplification of DNA isolated from nodules of G. australianum and E. triflora inoculated with Frankia str ain EL1 revealed, when compared with DNA amplified from free living Fr ankia strain EL1, that there was only one Frankia strain causing the o bserved nodules.