In vitro mycorrhization of Casuarina and Allocasuarina species by Pisolithus isolates
Five Casuarina species and five Allocasuarina species were inoculated in vitro with three isolates of Pisolithus sp. (Ors.X004 and Ors.7870 from Senegal, PR86 from Australia) to test their ability to form ectomycorrhizas. The mycorrhiza-forming ability varied between fungal isolates. The greatest differences occurred between Casuarina and Allocasuarina species. On Casuarina species, Pisolithus isolates formed only a fungal sheath. However, Ors.X004 induced well-developed ectomycorrhizas on Casuarina equisetifolia, whereas PR86 failed to form any fungal sheath on Casuarina cunninghamiana. On Allocasuarina species, Pisolithus isolates formed generally well-developed ectomycorrhizas. In addition, isolates Ors.7870 and PR86 invaded the cortical cells of Allocasuarina luehmannii and Allocasuarina decaisneana, respectively, thus forming ectendomycorrhizas. Epidermal cells of both Casuarina and Allocasuarina mycorrhizas showed tannin deposits. In fully developed ectomycorrhizas, the epidermal cells were radially elongated and the Hartig net never developed beyond the epidermal cells. In general, the ability to form ectomycorrhizas was more common with the genus Allocasuarina than the genus Casuarina.Key words: Casuarina, Allocasuarina, Pisolithus, ectomycorrhizas.