RAPD characterisation of heterogeneity in spore progenies and sexuality in the genus Agaricus

Induced mutation in Agaricus bisporus by gamma ray to improve genetic variability, degradation enzyme activity, and yield

PURPOSE

Genetic variability in white button mushroom cultivars is very low due to the life cycle. Induction mutations using gamma irradiation is a useful way to generate diversity in white button mushrooms to obtain genotype(s) with desirable traits.

METHODS

Gamma irradiation Cobalt-60 was used for inducting genetic diversity in white button mushroom to obtain genotype(s) with desirable traits. Gamma irradiation with doses of 0-500 Gy was conducted on spores on Potato Dextrose Agar medium.

RESULTS

The results showed significant differences in days to pin production and harvest, fruit body number, fresh and dry weight, yield, laccase, and manganese peroxidase enzyme activity. After isolating variants, 15 variants were selected on the base of their high yield and enzyme degradation activity. Their genetic variation was confirmed by Sequence Related Amplified Polymorphism (SRAP) markers, and then incubated on three types of substrates (50:50, 75:25, and 100:0 % compost: raw straw). The results showed that all variants, except GR18, colonized in 75:25, and GR3, GR4, GR9, GR61, GR72, and GR74 variants colonized in 50:50. In 100:0 substrate, GR55 and GR63 were the earliest variants, and GR9 produced the highest fruit body number. In 75:25 substrate, GR9, GR3, GR61, GR4, GR74, GR4, GR61, and GR72 showed higher yields. The highest laccase and manganese peroxidase activity were recorded in GR3, GR4, GR9, GR72, and GR61. The isolated 15 variants were clustered into two main groups by cluster analysis and genetic variation was confirmed by SRAP markers.

CONCLUSION

The results showed that the diversity in the white button mushroom could be improved using gamma rays, and the variation would be useful for the development of future breeding programs.

Evaluating Genetic Diversity of Agaricus bisporus Accessions through Phylogenetic Analysis Using Single-Nucleotide Polymorphism (SNP) Markers

Agaricus bisporus, commonly known as the button mushroom, is widely cultivated throughout the world. To breed new strains with more desirable traits and improved adaptability, diverse germplasm, including wild accessions, is a valuable genetic resource. To better understand the genetic diversity available in A. bisporus and identify previously unknown diversity within accessions, a phylogenetic analysis of 360 Agaricus spp. accessions using single-nucleotide polymorphism genotyping was performed. Genetic relationships were compared using principal coordinate analysis (PCoA) among accessions with known origins and accessions with limited collection data. The accessions clustered into four groups based on the PCoA with regard to genetic relationships. A subset of 67 strains, which comprised a core collection where repetitive and uninformative accessions were not included, clustered into 7 groups following analysis. Two of the 170 accessions with limited collection data were identified as wild germplasm. The core collection allowed for the accurate analysis of A. bisporus genetic relationships, and accessions with an unknown pedigree were effectively grouped, allowing for origin identification, by PCoA analysis in this study.

Comparison of random amplified polymorphic DNA markers and morphological characters in identification of homokaryon isolates of white button mushroom (Agaricus bisporus)

The secondarily homothallic life cycle of the white button mushroom that results in scarcity of uninucleate basidiospores (homokaryons) in its progeny, is the most important impediment for genetic improvement of the commercial strains. Identification of homokaryons for breeding programs of Agaricus bisporus (button mushroom) is, therefore, crucial. Verifying homokaryons through fruiting trial is time consuming and unreliable. In this study, ability of RAPD markers, compared to morphological characters for identification of homokaryon isolates, was investigated. Based on morphological characters, 42 isolates were screened and exposed to RAPD markers. The results showed that RAPD markers could discriminate homokaryons from heterokaryons, based on number of bands generated. The numbers of band in homokaryons were significantly less than those of heterokaryons. Results also showed that cluster analysis, based on average of band number generated, could separate homokaryon from heterokaryon isolates. It is suggested that RAPDs could be used to identify hyomokaryons from heterokaryons for breeding program of A. bisporus.

Mating systems in the genus Xanthoria (lichen-forming ascomycetes)

Genetic variability among sterile cultured single ascospore isolates of Xanthoria parietina, X. calcicola, X. ectaneoides, X. capensis, X. polycarpa and X. resendei was investigated with RAPD-PCR. If available five out of eight ascospores per ascus were analysed. In some samples multispore and mycelial isolates from ascomata were included in the analysis. Ascospore germination rates and phenotypic features such as growth rate, pigmentation and secondary metabolites were uniform in X. parietina sporelings of the same ascus, but varied among the progeny of meiosis in all other species. Phenotypic features correlated with genetic variability. X. parietina revealed polymorphisms among specimens from different worldwide locations. In contrast nine out of ten sets of sibling spores were genetically uniform, with only 2% polymorphism in the remaining set, indicating that X. parietina might be homothallic. X. calcicola, X. ectaneoides, X. capensis, X. polycarpa and X. resendei revealed 9-66% polymorphic loci and therefore are considered heterothallic.