Nucleotide Sequence-based Identification and Submerged Fermentation of Volvariella volvacea (Paddy Straw Mushroom) Isolates from the Philippines

Volvariella volvacea, generally known as paddy straw mushroom, is a nutritious and edible mushroom that is commercially cultivated in tropical countries such as the Philippines. This study highlights the molecular identification and the optimal nutritional and physical culture conditions of the three isolates of V. volvacea from the Philippines. Genomic DNA of mushroom mycelia were isolated and the ITS1F and ITS4BR amplicons-amplified were sequenced and compared against NCBI GenBank database. The Maximum Likelihood phylogenetic relationship was established using MEGA 7. BLASTn analysis confirmed the ITS sequence-based identities of the three isolates of V. volvacea with NCBI Accession Codes; OR052653, PQ671094, PQ671093. The constructed phylogenetic tree supported the clade grouping of La Union and San Jose isolates with V. volvacea ATCC strain (BS = 99%) and the separation of Tarlac isolate (BS = 88%), indicating its distinct lineage. Root crops-based culture media such as sweet potato, white yam and taro were evaluated for the submerged cultivation of V. volvacea mushrooms. Results revealed that sweet potato broth at pH 7 had the highest mycelial biomass yield of the three V. volvacea isolates. Light-incubated cultures yielded higher mycelial biomass than dark-incubated cultures. Cultures incubated at 30°C produced the highest biomass yield, while 4°C cultures showed no mycelial growth after 14 days. Static culture produced a significantly higher yield than those in agitated condition. Altogether, root crops particularly sweet potatoes can be promising nutrient sources of mycelial biomass production of the three molecularly confirmed isolates of V. volvacea and this can be improved by growing them in their best physical culture environments.