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The local environment is rich genetic and biological diversity, including large fungi, which are among its key components that have not been sufficiently studied. The commercial production of white mushrooms (Agaricus bisporus) still relies on some domesticated wild European strains. Moreover, spent mushroom compost remaining after the production cycle is worth investigating for reuse and to avoid its negative environmental impact. Therefore, this research was conducted as a new survey of the genus Agaricus spp., belonging to the Basidiomycetes fungi, in various regions of rural western Homs governorate during the years 2021 and 2022. The objective was to collect and describe wild strains of Agaricus spp., cultivate them, select the best-performing strains in terms of productivity and quality, and explore the development of mushroom substrates using spent compost and other nutritional supplements as potential alternatives to the costly traditional fermented substrates. The work included the following stages: 1- Collection and description of wild isolates. 2- Laboratory isolation and purification of these isolates. 3- Preparation of spawn from pure isolates. 4- Evaluate how successful is to grow pure isolates on commercial compost and comparing their productivity with imported control strains.5- Molecular characterization of successfully cultivated isolates and comparing growth and development of the selected isolate with the control strain on alternative substrates versus commercial compost. Samples were collected during regular field surveys, timed according to the growth and fruiting periods of these wild fungi. The studied fungal species were classified using various global taxonomic keys,depending on both morphological and microscopic characteristics. The study revealed that the surveyed areas are characterized by notable and abundant fungal diversity, where it resulted in the collection of 50 isolates. All were found to belong to the section Bivelares and genus Agaricus. The majority of them were found in areas ranging from 360 to 950 meters above sea level. Most species appeared during the months of November, December, and January. Six isolates succeeded in cultivation: B.R.5, B.R.9, B.R.17, B.R.22, B.R.42, and B.R.47. These were compared with the commercial control strain A.15. Molecular identification of these mushroom samples, using ribosomal DNA internal transcribed spacer (rDNA-ITS) sequences, revealed that they belong to three different species: A. bisporus (B.R.5, B.R.9; OP648153.1, OP648159.1), A. sinodeliciosus (B.R.17, B.R.42; OP648156.1, OP648154.1), and A. qilianensis (B.R.22, B.R.47; OP648155.1, OP648157.1). This information was registered in the GenBank database. The cultivation experiment was conducted on comercial compost at a mushroom farm in Tartus province. The results showed that the six studied isolates varied in growth stages and the formation of fruiting bodies. The time for full mycelial growth on the substrate ranged from 14 to 24 days, and the isolates took 8 to 14 days to reach the harvest stage. Significant differences were found among the studied isolates in terms of fruiting body growth and productivity indicators, with the average cap diameter ranging from 52.22 to 70.89 mm. Isolate B.R.22 was superior in terms of cap diameter, thickness, and stem length and diameter, while isolate B.R.17 stood out with the highest average number of fruiting bodies (60) and productivity (22.71 kg/m²) and biological efficiency (84.13%) compared to the control (33.33, 17.39 kg/m², and 64.40%, respectively). Chemical analyses of the fruiting bodies of the studied isolates were conducted at the General Commission for Scientific Agricultural Research in 2022. Significant differences were observed, with isolate B.R.47 showing the highest protein content (29.52% of dry weight), with no significant difference compared to the control (28.55%). All isolates had higher carbohydrate content compared to the control (p < 0.01), with isolate B.R.42 having the highest (72.24% of dry weight). Fat content in the studied isolates ranged from 1.68% to 5.34%, all lower than the control (7.29%). Isolate B.R.9 exhibited the highest phenolic content (1.93 mg/g of dry weight), while the control had the highest antioxidant activity (82.41% of dry weight). A strong correlation was observed between antioxidant activity, protein, fat, ash, and fiber. Some of the studied isolates demonstrated notable nutritional value and biological properties, suggesting their potential use for both dietary and pharmaceutical purposes. The study also examined the impact of adding spent mushroom compost and some nutritional supplements to the substrate on the growth, productivity, and chemical composition of white mushrooms Agaricus bisporus (the wild isolate B.R.5 and the commercial strain A.15). Eight different treatments were applied. The stages of mushroom production (the time required for full mycelial growth on the substrate and casing layer, pinhead formation period, days to harvest, and production cycle duration), fruiting body measurements, productivity, and biological efficiency, as well as the effects of treatments on chemical composition, were all studied. The results showed significant differences in the time required for full mycelial growth on the substrate between treatments for isolate B.R.5 and strain A.15. The shortest period (9 days) for full mycelial growth on the casing layer was observed for isolate B.R.5 in the control treatment (100% fresh compost, T1), with no significant differences between T1, T2 (75% fresh compost with 25% spent compost), and T7 (75% fresh compost with 25% supplements). For the commercial strain A.15, treatments T1 and T7 outperformed treatments T2 and T3 (50% fresh compost with 50% spent compost) with a growth period of 9.50 days. For pinhead formation, the shortest period was observed in treatments T1 and T2. Isolates B.R.5 showed superior cap diameter, thickness, and stem diameter and length in treatments T1 and T2.For A.15, superior cap diameter, thickness, and stem diameter were registered in T7, with no significant differences from T1. Treatment T1 significantly outperformed other treatments in both B.R.5 and A.15 in terms of productivity (20.50 and 20.31 kg/m², respectively) and biological efficiency (75.93% and 75.24%, respectively). Adding 25% spent compost or supplements increased protein and ash content but reduced biological efficiency and productivity. Therefore, further experiments are necessary to optimize the percentage and timing of adding spent compost and supplements to the growing substrate.
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