Background: The growing population and limited agricultural land have pushed the demand for higher food production per land area. Edible mushrooms are a rich source of protein. Agaricus bisporus is the most common edible mushroom with high economic value. One of the most important steps in the production process of white button mushroom is the production of spawn. It is highly important to make pure high-quality mycelium during the production of spawn. Studies have shown that at this stage of production, a high level of morphological changes occurs in some mushrooms, which causes the formation of fluffy-shaped mycelium. This phenomenon is a kind of strain degeneration in edible mushrooms and is one of the biggest concerns of the producers of white button mushroom. Objectives: The purpose of this study was to investigate the nature of stroma (strain degeneration) in white button mushroom, and to identify the causes of genetic changes. Methods: In this experiment, ten successive subcultures were produced from the mother mycelium on potato dextrose agar medium (pH: 6.2), and the genetic changes of mycelium were examined after ten successive subcultures. DNA extraction was performed after sampling of the mother, normal, and fluffy mycelia. Six pairs of designed primers and propagated parts were loaded into six polyacrylamide gels. DNA fragments were visualized using silver staining. Genetic comparisons were made between the mother, normal, and fluffy mycelia by the amplified fragment length polymorphism (AFLP) method, and the results were evaluated using POPGENE software. Results: The AFLP marker produced 137 fragments for the H2 strain, of which 57 fragments had polymorphism between the mother, normal, and fluffy mycelia. For the 737 strain, 149 fragments were produced, of which 73 fragments had polymorphism between the mother, normal, and fluffy mycelia. On average, the mother, normal, and fluffy mycelia had about 42 and 49% polymorphism for the H2 and 737 strains, respectively. The degree of polymorphism among the samples confirmed genetic differences between the mother, normal, and fluffy mycelia. Conclusions: Based on the results of the present study, we concluded that strain degeneration, which manifests as the fluffy mycelium of white button mushroom, has a genetic origin. These genetic differences can be attributed to diverse factors, such as the phenomenon of heterokaryosis, asexual recombination, and the formation of mitosis crossing over. These factors and their effects require further evaluations.

Background: Production and cultivation of edible mushrooms are one of the commercial applications of microbial technologies in order to biodegrad agricultural waste into valuable food products. One of the edible mushrooms that uses these agricultural wastes for its growth and development is Pleurotus florida. In P. florida, various enzymes are responsible for the decomposition of lignin compounds in the compost environment from the beginning of mycelial growth to the end of the fruiting period. One of the most important of these enzymes is manganese peroxidase (MnP), which plays a major role in the breakdown of lignin compounds. In addition, the most important compost-degrading mushroom that produces the enzyme MnP is Agaricus bisporus. Objectives: The aim of this study was to produce hybrids of P. florida by increasing the production efficiency through hyphae fusion of P. florida and the A. bisporus. Methods: The hyphae fusion and hybridization were performed for two strains P. florida and A. bisporus, in PDA culture media. Samples were isolated from the fusion areas and were transferred to the culture media, and then spawn was produced. Performance testing was carried out with hybrids and P. florida. We designed a specific primer pair of P. florida MnP gene by Primer Premier software (V.7.0). Polymerase chain reaction (PCR) was used to confirm the MnP gene. For this purpose, RNAs were extracted, and their cDNA was synthesized by reverse transcriptase enzyme. PCR with specific primers was performed, and electrophoresis was loaded on 1% agarose gel. Results: This study performed hybridization with formation clamp connections at the junction line. Hybrid N09 with biological efficiency (82.92) produced the highest performance in all evaluations compared to other hybrids and the parent strain. Based on the results of PCR product electrophoresis, banding pattern N09 (hybrid N09) indicated that this hybrid, in addition to the P. florida MnP gene of P. florida, also received the amino acid sequences of this gene in A. bisporus. Conclusions: According to the obtained results, the use of hyphae fusion increased the traits as a result of mixing the genetic contributions of parent strains, followed by the diversity of hybrid strains and increased production yield.