Variability in intra-specific and monosporous isolates of Volvariella volvacea based on enzyme activity, ITS and RAPD.

Two parents and 15 monosporous isolates were morphologically characterized and were found to vary in their growth characteristics on malt extract agar medium. The isolates also varied in enzymes activity profile with respect to exoglucanase, endoglucanase, xylanase, laccase and polyphenol oxidase. Further in polymerase chain reaction (PCR) amplification of Internal Transcribed Spacer (ITS) region of 5.8S rDNA, an amplicon of same length (720 bp) was amplified from two parents and all the monosporous isolates, which revealed that all belong to the same species. The combined phylogenetic analysis of random amplified polymorphic DNA (RAPD) profiles obtained with five decamer primers (operon kit B) series primers also revealed intra-specific variation of 60% with in the two parent strains and their single spore isolates (SSIs). However, the variations between the parent strains and their SSIs were lesser and it was 50 and 32% in parent strains, OE-210 and OE-12, respectively. Based upon phylogenetic analysis, the isolates of parent strain, OE-210 formed 7 distinct phylogenetic clades, while of strain OE-12 formed 4 clades. The study elucidates that isolates showing variations in morphological growth characteristics and enzymes activity also showed variations in their RAPD profiles, revealed through phylogenetic analysis of RAPD profiles. It is also evident from the study that morphological characterization along with enzymes activity assay of strains is essential before their use in yield evaluation trials with final authentication from molecular analysis.

Profile of the extracellular lignocellulolytic enzymes activities as a tool to select the promising strains of Volvariella volvacea (Bull. ex Fr.) sing.

Out of 26 strains of Volvariella volvacea used, 18 were of 'typical' type and possessed all the characteristics of a normal V. volvacea mycelium, while the rest 4 'atypical' type strains showed completely distinct mycelial growth characteristics. The remaining 4 strains grew very slowly and exhibited growth characteristics of single spore isolates of V. volvacea. Strains varied in their extracellular lignocellulolytic activities and strains; OE-274, OE-272 and OE-210 with high ligninase enzymes (laccase and polyphenol oxidase) activities, gave highest mushroom yield on pasteurized paddy straw substrate. On the composted paddy straw substrate, additional two strains, OE-213 and OE-215 with lower activities of ligninases also gave higher mushroom yield. Mushrooms were harvested 3 to 4 d early from the composted substrate than on the pasteurized substrate. Activities of endoglucanase, laccase and polyphenol oxidase were found to be more crucial for mushroom yield on pasteurized substrate, while xylanase and ß-glucosidase were more important for composted substrate. Strains also varied in their fruiting bodies quality and the substrate used for mushroom cultivation also affected the fruiting body quality. The superior yielding strains varied in shape, size, weight, colour and contents of sodium and potassium in their fruiting bodies; while contents of carbon, calcium and protein did not vary much with the strains.