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Protoplast fusion technology originated from cell-cell fusion technology in the 1950s and was initially applied to animal cells. The advantage of applying it in the field of edible fungi breeding is that compared with conventional natural selection and hybrid breeding methods, it could more effectively overcome certain incompatibility obstacles to achieve distant hybridization, and more purposefully select parents to obtain new varieties with outstanding characteristics. For these reasons protoplast fusion technology is becoming of great significance for the improvement of edible fungi strains, the breeding of new varieties, and the taming of difficult-to-cultivate species. At present, relatively stable and capable-of-fruiting fusants are limited to several genus and species, and using protoplast fusion for distant hybridization requires new breakthroughs overcoming vegetative incompatibilities. Technically, the acquisition and identification of fusants could also be improved to a more controllable approach. This article focuses on the longitudinal discussion of the role of protoplast fusion technology in the genetic breeding of edible fungi. It explains: i) the preparation and regeneration of protoplasts in the process, ii) the specific methods of fusion, iii) the identification, mutagenesis, and rejuvenation of fusants, and iv) possible impacts of two incompatible systems. Certain application practice cases are also introduced to summarize its promotion prospects.

Characterization of the Cryphonectria parasitica population was initially done by a phenotypical assessment of 40 in vitro grown isolates obtained from 52 healing cankers collected from eight important chestnut-growing provinces of Turkey. The results of Bavendamm test, often correlated indirectly to hypovirulence, suggested 31 possibly hypovirulent and 9 virulent isolates. PCR tests amplified two regions of ORFs A and B of Cryphonectria hypovirus 1 (CHV-1) from 36 of 40 isolates. The PCR test confirmation was more sensitive than the Bavendamm test. Partial ORFA sequencing revealed 36 CHV-1 haplotypes belonging to Italian subtype (I), with all hypovirulent isolates being of EU-1 vc type. The CHV-1 from 10 native EU-1 isolates were first transferred to six European vc type testers, EU-2, EU-3, EU-5, EU-7, EU-26, and EU-44, having heteroallelism at one vic locus. The presence of the vic locus difference generally reduces virus transmission. The easiest and highest frequency virus transfer was obtained by vic4 and vic6 allelic differences, while the differences vic2 and vic7 made the transfer more challenging. Finally, in this study we successfully transferred CHV-1 to an EU-1 isolate obtained from the Bursa province to an EU-12 European tester isolate. [ABSTRACT FROM AUTHOR]

Endornaviruses are known to occur widely in plants, fungi, and oomycetes, but our understanding of their diversity and distribution is limited. In this study, we report the discovery of four endornaviruses tentatively named Setosphaeria turcica endornavirus 1 (StEV1), Setosphaeria turcica endornavirus 2 (StEV2), Bipolaris maydis endornavirus 1 (BmEV1), and Bipolaris maydis endornavirus 2 (BmEV2). StEV1 and StEV2 infect Exserohilum turcicum, while BmEV1 and BmEV2 infect Bipolaris maydis. The four viruses encode a polyprotein with less than 40 % amino acid sequence identity to other known endornaviruses, indicating that they are novel, previously undescribed endornaviruses. However, StEV1 and BmEV1 share a sequence identity of 78 % at the full-genome level and 87 % at the polyprotein level, suggesting that they may belong to the same species. Our study also found that each of the four endornaviruses has an incidence of approximately 3.5 % to 5.5 % in E. turcicum or B. maydis. Interestingly, BmEV1 and BmEV2 were found to be unable to transmit between hosts of different vegetative incompatibility groups, which may explain their low incidence.

Hyperparasites can affect the evolution of pathosystems by influencing the stability of both pathogen and host populations. However, how pathogens of perennial hosts evolve in the presence of a hyperparasite has rarely been studied. Here, we investigated temporal changes in genetic diversity of the invasive chestnut blight pathogen Cryphonectria parasitica in the presence of its parasitic mycovirus Cryphonectria hypovirus 1 (CHV1). The virus reduces fungal virulence and represents an effective natural biocontrol agent against chestnut blight in Europe. We analysed genome‐wide diversity and CHV1 prevalence in C. parasitica populations in southern Switzerland that were sampled twice at an interval of about 30 years. Overall, we found that both pathogen population structure and CHV1 prevalence were retained over time. The results suggest that recent bottlenecks have influenced the structure of C. parasitica populations in southern Switzerland. Strong balancing selection signals were found at a single vegetative incompatibility (vic) locus, consistent with negative frequency‐dependent selection imposed by the vegetative incompatibility system. High levels of mating among related individuals (i.e., inbreeding) and genetic drift are probably at the origin of imbalanced allele ratios at vic loci and subsequently low vc type diversity. Virus infection rates were stable at ~30% over the study period and we found no significant impact of the virus on fungal population diversity. Consequently, the efficacy of CHV1‐mediated biocontrol was probably retained. [ABSTRACT FROM AUTHOR]

• We have characterised the first vic locus in Botrytis cinerea using a bulked segregant approach. • The locus comprises two adjacent, highly polymorphic open reading frames, Bcvic1 and Bcvic2 , which encode predicted proteins that contain domain architectures implicated in vegetative incompatibility. • Bcvic1 encodes a putative protein with a serine esterase domain, a NACHT family of NTPases domain, and several Ankyrin repeats. • Bcvic2 encodes a putative syntaxin protein containing a SNARE domain; such proteins typically function in vesicular transport. • Deletion of Bcvic1 and Bcvic2 individually had no effect on vegetative incompatibility, however, deletion of both Bcvic1 and Bcvic2 resulted in mutant lines that were severely restricted in growth and showed loss of vegetative incompatibility. • Complementation of these mutants by ectopic expression restored the growth and vegetative incompatibility phenotype, indicating that Bcvic1 and Bcvic2 are controlling vegetative incompatibility at this vic locus. Vegetative incompatibility is a fungal allorecognition system characterised by the inability of genetically distinct conspecific fungal strains to form a viable heterokaryon and is controlled by multiple polymorphic loci termed vic (v egetative i n c ompatibility) or het (het erokaryon incompatibility). We have genetically identified and characterised the first vic locus in the economically important, plant-pathogenic, necrotrophic fungus Botrytis cinerea. A bulked segregant approach coupled with whole genome Illumina sequencing of near-isogenic lines of B. cinerea was used to map a vic locus to a 60-kb region of the genome. Within that locus, we identified two adjacent, highly polymorphic open reading frames, Bcvic1 and Bcvic2 , which encode predicted proteins that contain domain architectures implicated in vegetative incompatibility in other filamentous fungi. Bcvic1 encodes a predicted protein containing a putative serine esterase domain, a NACHT family of NTPases domain, and several Ankyrin repeats. Bcvic2 encodes a putative syntaxin protein containing a SNARE domain; such proteins typically function in vesicular transport. Deletion of Bcvic1 and Bcvic2 individually had no effect on vegetative incompatibility. However, deletion of the region containing both Bcvic1 and Bcvic2 resulted in mutant lines that were severely restricted in growth and showed loss of vegetative incompatibility. Complementation of these mutants by ectopic expression restored the growth and vegetative incompatibility phenotype, indicating that Bcvic1 and Bcvic2 are controlling vegetative incompatibility at this vic locus. [ABSTRACT FROM AUTHOR]