Genetic variability of Pisolithus isolates associated with native hosts and exotic eucalyptus in the western Mediterranean region

Abstract

Summary• Genetic diversity and host specificity of Pisolithus is reported here in exotic ( Eucalyptus ) and native hosts in the western Mediterranean region.• Polymorphism in the internal transcribed spacer (ITS) sequences of the nuclear rDNA of Pisolithus was analysed. Sequences for 17 isolates associated with native Mediterranean hosts and Eucalyptus were compared with those in the GenBank DNA database using distance and parsimony methods.• Bootstrap analysis showed clustering of all Pisolithus isolates associated with Mediterranean hosts. The ITS sequences suggest the occurrence of several ecological species adapted to exploit different soil types (basic, acid and clayey slate-derived soils), with specificity for particular indigenous hosts. Isolates from eucalypt plantations in Brazil, Kenya and the Mediterranean grouped together with eucalypt-associated Australian isolates. Transfer to native hosts did not occur; the host specificity range of these exotic strains might prevent out-competition and interbreeding with local species.• Pisolithus spp. in eucalypt plantations in the Mediterranean basin are of Australian origin; the co-introduction of the ectomycorrhizal fungi might explain the success of these exotic forest plantations.

Molecular phylogeny of ectomycorrhizal Pisolithus fungi associated with pine, dipterocarp, and eucalyptus trees in Thailand

“…Variation in restriction fragment length polymorphism (RFLP) of ribosomal DNA and internal transcribed spacer (ITS) regions and nucleotide sequence difference in those regions have also been used to investigate phylogeny within Pisolithus. Such investigations have been reported on Pisolithus in Australia, Kenya, Europe, North America, South East Asia, and Brazil (Anderson et al 1998(Anderson et al , 2001Martin et al 1998;Sims et al 1999;Gomes et al 2000;Díez et al 2001). Recently, an overall Pisolithus phylogeny by ITS sequence analysis has been reported, showing that a number of Pisolithus species exist worldwide (Martin et al 2002).…”

“…Coker and Couch. However, variations within the former P. tinctorius were found in various enzyme activities, growth rates (Ho 1987), sexual incompatibility , mycorrhiza-forming ability (Lamhamedi et al 1990), electrophoretic protein profiles (Burgess et al 1995), and host specificity (Anderson et al 1998(Anderson et al , 2001Martin et al 1998Martin et al , 2002Díez et al 2001). In addition, considerable large variations in morphology in basidiomes, basidiospores, and cultured mycelia also occur within P. tinctorius (Chambers and Cairney 1999).…”

“…Many investigators have been interested in the phylogeny of Pisolithus (Anderson et al 1998(Anderson et al , 2001Martin et al 1998Martin et al , 2002Gomes et al 2000;Díez et al 2001). Formerly, most Pisolithus isolates were classified as P. tinctorius (Pers.)…”

Morphological and molecular characterization of Pisolithus in soil under eucalyptus plantations in Brazil

“…The origin of Pisolithus spp. in eucalypt plantations in the Mediterranean basin is Australia; the co-introduction of the ectomycorrhizal fungi might explain the success of these exotic forest plantations (Díez et al, 2001). …”

“…The dispersal of ectomycorrhizal trees, such as eucalyptus and pine, outside their natural range, has resulted in the introduction of a narrow range of exotic ectomycorrhizal fungi into forest plantations in many countries of Europe, South America, Africa and Asia (Garbaye et al, 1988;Martin et al, 1998;Gomes et al, 2000;Díez et al, 2001;Singla et al, 2004;Reddy et al, 2005). Whether the distribution of these fungi reaches beyond these areas depends on the host range of the fungi and their ability to compete with indigenous species.…”