Screening of a selenium-enriching strain of Pleurotus ostreatus by ultraviolet mutagenesis and its application in nutrient enrichment

Abstract:

[Background] The cultivation of selenium-enriching edible fungi in their natural habitats often fails to meet the national standards for nutrient enrichment. [Objective] To screen out a selenium-enriching strain of Pleurotus ostreatus by ultraviolet mutagenesis, so as to provide a foundation for the product development with selenium-enriching edible fungi. [Methods] The strain to be mutated was determined by selenium resistance examination and then exposed to ultraviolet irradiation. The mycelial growth rate and the biological efficiency, total and organic selenium content of fruiting bodies were determined to evaluate the performance of the mutant strain. [Results] In the media with 100 mg/kg and 120 mg/kg selenium, respectively, the strain 120-5 showed the mycelial growth rates of 1.27 cm/d and 1.19 cm/d and the total selenium content of 199.77 mg/kg and 224.15 mg/kg in the fruiting bodies of 120-5. The organic selenium content in the fruiting bodies in the two treatments reached 198.83 mg/kg and 223.56 mg/kg, accounting for 99.53% and 99.74% of the total selenium, respectively. These values met the national standards for nutrient enrichment. However, in the media with 100 mg/kg and 120 mg/kg selenium, the original strain qiu-2020 showed the mycelial growth rates of 1.02 cm/d and 0.88 cm/d, respectively. It is noteworthy that in the medium with 120 mg/kg selenium, the original strain achieved the highest selenium content of 166.53 mg/kg, which fell short of the national standards. In the presence of 120 mg/kg selenium, the biological efficiency of the mutant strain and the original strain reached 92% and 77%, respectively. Remarkably, the agronomic traits of both the mutant and original strains remained unaltered. The whole-genome resequencing results unveiled single nucleotide polymorphism (SNP), insertion-deletion (Indel), and structure variation (SV) between the mutant and original strains. [Conclusion] The strain 120-5 with significant genomic mutations showcased a robust capacity of selenium enrichment, serving as a compelling candidate for nutrient enrichment.