Phylogeny of the Botryosphaeriaceae reveals patterns of host association

Most of the species of the Botryosphaeriaceae cause disease symptoms such as die-back and cankers on numerous woody and non-woody hosts, especially in combination with stress-inducing environmental conditions.  A recent broad-based phylogenetic study recognized ten genera in the Botryosphaeriaceae.  These are Diplodia/Lasiodiplodia/Tiarosporella, Botryosphaeria (Fusicoccum anamorphs), Macrophomina, Neoscytalidium, Dothidotthia (Dothiorella anamorphs), Neofusicoccum (Botryosphaeria-like teleomorphs, Dichomera-like synanamorphs), Pseudofusicoccum, Saccharata (Diplodia- and Fusicoccum-like synanamorphs), “Botryosphaeria” quercuum (Diplodia-like anamorph) and Guignardia (Phyllosticta anamorphs).

The profusion of ITS sequence data that has become available for members of the Botryosphaeriaceae has made it possible to explore general patterns of host association in six lineages of the Botryosphaeriaceae (excluding Macrophomina, Guignardia, Saccharata and “Botryosphaeria” quercuum).  Most species (Dothiorella, Neofusicoccum, Botryosphaeria, Pseudofusicoccum and Neoscytalidium) have been reported only from angiosperms.  In a few cases (Lasiodiplodia spp., D. mutila and D. seriata), from angiosperms and gymnosperms and only D. pinea, D. scrobiculata and D. cupressi are known exclusively from gymnosperms.  Angiosperms thus appear to be the most common, and possibly ancestral, host group of the Botryosphaeriaceae.  Infection of gymnosperms most likely occurred more recently in specific groups via host shifts. 

Furthermore it is clear that host association is not always a good indication of species delineation in the Botryosphaeriaceae.  Some are clearly generalist species, able to infect a wide range of unrelated hosts, while others are more specialized and appear to infect only a specific host genus.  Host association patterns are, however important when seeking to understand the driving forces of evolution in the group, as well as patterns of co-evolution with specific hosts.  This will ultimately assist towards understanding their epidemiology, the potential emergence of new diseases and managing their threat to forestry and agriculture.

References

De Wet J,  Slippers B, Preisig O,  Wingfield BD, Wingfield MJ. 2008.  Phylogeny of the Botryosphaeriaceae reveals patterns of host association.  Molecular Phylogenetics and Evolution 46, 116-126.

Figure: Phylogram constructed for the ITS and 5.8S rDNA based on neighbour-joining distance analysis with branch support values (maximum parsimony bootstrap proportions). Gymnosperm/angiosperm character states were traced in MacClade. Isolates marked with red are from Gymnosperms and isolates marked with yellow are from Angiosperms. Isolates marked with an asterisk * are from Pinus spp. Pinus is arguably the most extensively sampled host for the Botryosphaeriaceae.