Species Delimitation and Host Specialization of Ceratocystis laricicola and C. polonica to Larch and Spruce

Abstract

Ceratocystis laricicola and C. polonica are fungal symbionts of bark beetle species of the genus Ips that attack species of Larix and Picea, respectively, across Eurasia. Earlier studies found that these fungal species were morphologically identical, had similar isozymes patterns, and had identical internal transcribed spacer (ITS) sequences of the rDNA operon. We analyzed 27 isolates from Europe, southwestern Siberia (Russia) and Japan, representing the known geographic ranges of the two species. Phylogenetic analysis of the DNA sequences of a portion of the MAT-2 idiomorph showed these species to be distinct, with the Japanese isolates of C. laricicola having a sequence slightly different (5 bp) from those of the Russian and European isolates of C. laricicola. Sexual compatibility tests showed full interfertility among isolates of C. polonica from Europe, Russia and Japan, but isolates of C. polonica were not fully interfertile with isolates of C. laricicola. A Russian and a European isolate of C. laricicola mated with each other but not with the Japanese isolates of C. laricicola. Mature L. sibirica and P. obovata were inoculated with isolates of C. laricicola and C. polonica from Europe, Russia, and Japan, and measurement of lesions in the inner bark/cambium region demonstrated strong host specialization. The data suggest that the two fungal species are very closely related and are distinguished primarily by their physiological specialization to the hosts of their bark beetle vectors.

Genetic diversity and interfertility among highly differentiated populations of Ceratocystis fimbriata in Brazil

“…Although some of the Brazilian populations were highly differentiated from each other, mating studies indicated that they constitute a single biological species that is interfertile with C. fimbriata from sweet potato on which the species is based (Engelbrecht & Harrington, 2005). By contrast, crosses between different species of Ceratocystis produce no interaction when paired, or they form only a few perithecia with few ascospores that are misshapen, germinate poorly and produce colonies of aberrant morphology and aberrant segregation of markers (Harrington & McNew, 1997; Harrington et al. , 2002; Engelbrecht & Harrington, 2005; Johnson et al.…”

“…Cultures were observed for 4 weeks for the presence of perithecia and ascospore masses. Ascospore masses were examined microscopically (×400) to see if there were abundant, normal‐appearing ascospores (indicative of an interfertile cross) or if there were few or no ascospores, or if the ascospores were misshapen, which is typical of an interspecific cross or hybrid (Harrington & McNew, 1998; Harrington et al. , 2002).…”

Single sequence repeat markers reflect diversity and geographic barriers in Eurasian populations of the conifer pathogen Ceratocystis polonica

“…Isolates of C. polonica associated with I. typographus in Europe and I. typographus japonicus in Japan are morphologically indistinguishable (Y amaoka et al. 1997), interfertile with each other (H arrington et al. 2002) and phylogenetically closely related (H arrington et al.…”

“…1997), interfertile with each other (H arrington et al. 2002) and phylogenetically closely related (H arrington et al. 2002; M arin et al.…”

Multigene phylogenies of Ophiostomataceae associated with Monterey pine bark beetles in Spain reveal three new fungal species

“…Bark beetles that infest conifers carry many different ophiostomatoid fungi including those related to Ophiostoma (Jacobs and Kirisits 2003;Kim et al 2003;Zhou et al 2004Zhou et al , 2006Kirisits 2007;Romon et al 2007;Linnakoski et al 2008Linnakoski et al , 2009Masuya et al 2009;Jankowiak and Kolarik 2010;Linnakoski et al 2010;Paciura et al 2010) and Ceratocystis (Harrington and Wingfield 1998, Harrington et al 2002, van Wyk et al 2004, Viiri and Lieutier 2004, Reid et al 2010. Although many of these fungi have the ability to cause lesions when inoculated into conifers (e.g.…”