Mitochondrial Haplotype Influences Mycelial Growth of Agaricus bisporus Heterokaryons

Abstract

We evaluated the influence of mitochondrial haplotype on growth of the common button mushroom Agaricus bisporus. Ten pairs of heterokaryon strains, each pair having the same nuclear genome but different mitochondrial genomes, were produced by controlled crosses among a group of homokaryons of both wild and commercial origins. Seven genetically distinct mitochondrial DNA (mtDNA) haplotypes were evaluated in different nuclear backgrounds. The growth of heterokaryon pairs differing only in their mtDNA haplotypes was compared by measuring mycelial radial growth rate on solid complete yeast medium (CYM) and compost extract medium and by measuring mycelial dry weight accumulation in liquid CYM. All A. bisporus strains were incubated at temperatures similar to those utilized in commercial production facilities (18, 22, and 26°C). Statistically significant differences were detected in 8 of the 10 heterokaryon pairs evaluated for one or two of the three growth parameters measured. Some heterokaryon pairs showed differences in a single growth parameter at all three temperatures of incubation, suggesting a temperature-independent difference. Others showed differences at only a single temperature, suggesting a temperature-dependent difference. The influence of some mtDNA haplotypes on growth was dependent on the nuclear genetic background. Our results show that mtDNA haplotype can influence growth of A. bisporus heterokaryons in some nuclear backgrounds. These observations demonstrate the importance of including a number of mitochondrial genotypes and evaluating different nuclear-mitochondrial combinations of A. bisporus in strain improvement programs. Agaricus bisporus (Lange) Imbach is a common edible mushroom with major economic value and a cosmopolitan distribution (24). The worldwide commercial production of this mushroom is valued at approximately 1.5 billion U.S. dollars annually (5). Mushroom producers depend primarily upon a limited number of superior genotypes of A. bisporus, specifically, the Horst U1 and U3 hybrids and their derivatives (8, 26). These commercially exploited genotypes are limited in genetic diversity (26, 40). The potential for selecting novel phenotypes in breeding programs from this limited gene pool is problematic and is an obstacle for mushroom strain improvement (29). Their limited genetic diversity also makes these cultivars more vulnerable to disease epidemics (34, 39). In addition, strain degeneration has been associated with some of these cultivars (14, 33). Each of these problems is a concern, since it may significantly reduce yields and prove to be costly to the grower. Indigenous populations of A. bisporus have been described for disparate locations in Europe, North America, and Asia (24) and include both bisporic (secondarily homothallic) and tetrasporic (heterothallic) isolates (3, 27). Some North American isolates have been identified as escaped commercial cultivars of European origin (24, 25, 28, 49). Xu et al. (48, 49) determined that genotypes isolated from indigenous A. bisporus...

Insight into the evolutionary and domesticated history of the most widely cultivated mushroom Agaricus bisporus via mitogenome sequences of 361 global strains

“…Similarly, in Clade Europe III, IDP11 has one fewer intron (intron 25) than IDP10. Our results also suggest that a specific intron missing from cox1 has occurred widely in the domesticated strains, and this phenomenon is consistent with previous reports [ 84 , 85 ]. Two hypotheses are proposed about how the cox1 introns changed in domestication.…”

FISHing in fungi: Visualisation of mushroom virus X in the mycelium of Agaricus bisporus by fluorescence in situ hybridisation

“…Agar plugs of A. bisporus cultures were placed on top of the thin, flat layer of solid media and incubated at 25 °C for one week, in the dark. CYM was considered a suitable medium to use in this study as it is commonly used to cultivate A. bisporus mycelium in vitro (De La Bastide et al, 1997;Kaur et al, 2011;Li et al, 1994;Masoumi et al, 2015). Control steps were taken to ensure CYM did not harbour problematic levels of nascent autofluorescence that would impede fluorescence observations (data not shown).…”