Influence of gibberellin on cultural and growth characteristics of vegetative mycelium of fungi strains of the genus Pleurotus during cultivation on agarized nutrient media
Authors:   Ukrainian State University of Chemical Technology, Kuznetsova O. 
Published: January 2021

Very slow introduction into the culture of new for Ukraine species of edible fungi is associated primarily with more difficult conditions for the cultivation of these fungi, slow growth of mycelium, difficulties in obtaining a pure culture, sterilization of the substrate and others. Therefore, it is important to study the possibility of using growth stimulants used in crop production in industrial mushroom growing in order to intensify the process of obtaining the mycelium and fruiting bodies of mushrooms. The aim of this experiment was to study the nature of the influence of gibberellin on the cultural and growth characteristics of the vegetative mycelium of strains of the genus Pleurotus, which are classified as medium- and slow-growing on agar nutrient media. The objects of the study were industrial strains of Pleurotus pulmonarius (Fr.) Quél. (strain IBK-230) (medium-growing), Pleurotus eryngii (DC.) Quél. (strains IBK-2011 and IBK-1972) (slow-growing) obtained from the Collection of cap mushrooms of the Institute of Botany named after N.G. Kholodny NAS of Ukraine. The following nutrient media were used in the study: corn agar (CA), crushed sunflower husk agar (SHA), glucose-ammonium (GAM) and glucose-asparagine (GAS) agars. Gibberellin was added to the nutrient media in the following concentrations: 1, 10, 50, 100 mg / dm3. The control media did not contain growth stimulant.Preparation and sterilization of nutrient media, tests for individual enzymes were performed according to conventional methods. 9-day crops grown on corn agar on Petri dishes were used as inoculum. Surface cultivation of the mycelium of the studied strains of mushrooms was performed in a thermostat at a temperature of 26 ± 1 °C.During the cultivation process, the radius of colonies on Petri dishes was measured daily, morphological description was performed, the duration of the lag-phase of mycelial growth on media with different concentrations of gibberellin, the average rate of radial mycelial growth (mm / day) and qualitative color reactions to phenoloxidases (laccases, tyrosinases, peroxidases) was determined. Data processing was performed by methods of mathematical statistics.According to the results of the study of cultural and morphological characteristics of colonies of P. pulmonarius, P. eryngii, it was determined that the applied concentrations of gibberellin do not have a significant effect on the morphological parameters of fungal colonies on agar nutrient media.Taking into account the data of the average daily growth of mycelium of the studied Pleurotus strains on agar nutrient media and the average duration of the lag-phase of growth of fungal colonies, the following can be stated. For P. pulmonarius, a significant positive effect of gibberellin on the lag-phase of growth was observed on the media CA, SHA, GAM – for a stimulant concentration of 1 mg / dm3 (9, 10 and 18%, respectively), CA and SHA – for a concentration of 10 mg / dm3 (9 and 10%, respectively), and on the SHA – for a concentration of 50 mg / dm3 – 20% compared with the control. Gibberellin had the best effect on the duration of the lag-phase of growth of the mycelium of P. eryngii IBK-2011, where the reduction of the lag-phase of growth ranged from 8 to 18% for all concentrations of growth regulator compared to the control.The average rate of radial growth of the mycelium of P. pulmonarius IBK-230 significantly increased compared with the control under the influence of all studied concentrations of gibberellin on the media CA (from 16.8 to 18.8%) and GAM (from 26.3 to 52.6%). The best indicator of linear growth rate was recorded on CA and GAM media with a concentration of gibberellin of 50 mg / dm3. The obtained data from the average radial growth rate of mycelium of slow-growing strains of P. eryngii (IBK-2011, IBK-1972) showed that these strains respond better to the growth stimulator gibberellin: on all nutrient media there was an increase of the growth rate for almost all concentrations of gibberellin from 3.1 to 60%. The most effective concentrations of gibberellin were 10 and 50 mg / dm3 (on the nutrient media of CA and GAM) for all strains of the studied fungi, on GAS – 1, 10 and 50 mg / dm3.The enzymatic activity of the studied strains differed depending on the type of mushrooms, nutrient medium and different concentrations of gibberellin. Thus, for P. pulmonarius no significant difference was found in the manifestation of color reactions to phenoloxidases, except for the enzyme tyrosinase, where the color appeared after 30 minutes on SHA (the concentration of gibberellin – 10 and 50 mg / dm3) and GAM (the concentration of 1 and 10 mg / dm3), on others the corresponding color appeared within 3 hours. The manifestation of color reactions to phenoloxidases for P. eryngii (IBK-2011, IBK-1972) for 30 minutes was observed on CA medium (concentration of gibberellin – 10, 50 and 100 mg / dm3), on SHA – 10 and 50 mg / dm3, on GAM – 1 and 10 mg / dm3, on GAS – 1, 10, 50 and 100 mg / dm3. Thus, slow-growing strains are more responsive to synthetic activity on this growth stimulant.As a result of the experiment it was found that the growth stimulant gibberellin affects the culture and growth characteristics of the vegetative mycelium of industrial strains of the genus Pleurotus, belonging to the medium- and slow-growing – P. pulmonarius (strain ІВК-230), P. eryngii (strains ІВК-2011, ІВК-1972): the lag-phase of mycelial growth decreases (on average from 8 to 18%), the average radial growth rate of mycelium increases from 16.8 to 57.9% for P. pulmonarius, and from 10.5 to 60% for strains P. eryngii, increases enzymatic activity. This growth stimulant can be used in biotechnology of edible fungi to obtain uterine mycelium of slow-growing species, increase the synthesis of biologically active substances by macromycetes, as well as increase the yield of fruiting bodies of mushrooms, which are poorly represented in the consumer market of Ukraine.