Genetic diversity of Amylostereum areolatum, the fungal symbiont of the invasive woodwasp Sirex noctilio in South Africa

Abstract

Amylostereum areolatum is a wood‐decaying homobasidiomycete fungal symbiont of Sirex noctilio. Together, they cause serious damage to pine plantations in the Southern Hemisphere. The fungus reproduces asexually and is vertically transmitted by S. noctilio females, which results in extensive spread of clones. Specific A. areolatum clones are often dominant in areas invaded by the wasp. This is in contrast with the high diversity and complex invasion pattern of S. noctilio in most of these regions. In South Africa, for example, nuclear and mitochondrial ribosomal loci and vegetative compatibility group (VCG) markers on a small number of isolates have shown that only one genotype is present in the country. The aim of this study was to develop microsatellite markers for A. areolatum and determine the genetic diversity and structure of a relatively large collection of isolates of the fungus in South Africa. From five sequenced A. areolatum genomes, a total of 233 microsatellite primer pairs were designed, of which 57 were polymorphic among the genomes. Eleven of these polymorphic markers were then used in a population genetics study including 55 South African isolates. In a surprising manner, nine multilocus genotypes were found among these isolates, and with no population structure among different regions across South Africa. The single VCG previously identified for isolates from the country clearly do not correspond to a clone. The detected A. areolatum variation has relevance for the biology of the Sirex‐Amylostereum symbiosis, its introduction history into South Africa and its management through biocontrol. The microsatellite primers and data emerging from them also provide powerful tools for the study of A. areolatum populations in other parts of the world.

Highly transferable microsatellite markers for the genera Lasiodiplodia and Neofusicoccum

“…cross-species transferability. Other studies have also used SSR-containing sequences, extracted from fungal genome sequences, to develop SSR markers (Jia et al 2015;Mercière et al 2015;Fortuna et al 2016;Wang & Chilvers 2016;Yu et al 2016;Vaghefi et al 2017;Bhat et al 2018;Mlonyeni et al 2018). These studies generally develop much larger numbers of SSR markers than studies using other approaches.…”

Fungal genomes enhance our understanding of the pathogens affecting trees cultivated in Southern Hemisphere plantations

“…More recently, however, the easy access to genome data has provided opportunities for the in-silico identification of microsatellites using genome comparisons (Hoffman and Nichols 2011). This approach has been used to identify microsatellite markers for a wide range of fungi, including pathogens of trees important to plantation forestry in the tropics and Southern Hemisphere (Cai et al 2013;Simpson et al 2013;Jia et al 2015;Mercière et al 2015;Mlonyeni et al 2018;Varady et al 2019). In fact, using comparative genomics, makes it possible to design these markers such that they function across several species or even across genera (Leyva-Madrigal et al 2014;Bhat et al 2018).…”