Cellulase enhances endophytism of encapsulated Metarhizium brunneum in potato plants

Krell V, Jakobs-Schönwandt D, Vidal S, Patel A. Cellulase enhances endophytism of encapsulated Metarhizium brunneum in potato plants. Fungal Biology. 2018;122(5):373-378.The recent discovery that entomopathogenic fungi can grow endophytically in plant tissues has spurred research into novel plant protection measures. However, current applications of fungi aiming at endophytism mostly lack targeted formulation strategies resulting in low efficacy. Here, we aimed at enhancing Metarhizium brunneum CB15 endophytism in potato plants by (i) improvement of fungal growth from beads and (ii) cellulase formation or addition to encapsulated mycelium. We found that beads supplemented with cellulose alone or in addition with inactivated baker's yeast exhibited cellulase activity and increased mycelial growth by 12.6 % and 13.6 %, respectively. Higher enzymatic activity achieved by cellulase co-encapsulation promoted a shift from mycelial growth to spore formation with maximum numbers of 2.5 × 108 ± 6.1 × 107 per bead. This correlated with improved endophytism in potato plants by 61.2 % compared to non-supplemented beads. Our study provides first evidence that customized formulations of fungal entomopathogens with enzymes can improve endophytism and this may increase efficacy in plant protection strategies against herbivorous pests

Encapsulation of Metarhizium brunneum enhances endophytism in tomato plants

Krell V, Jakobs-Schönwandt D, Vidal S, Patel A. Encapsulation of Metarhizium brunneum enhances endophytism in tomato plants. Biological Control. 2017;2018(116):62-73.Biocontrol of insect pests using fungal entomopathogens has been promoted as a promising alternative to chemical pesticides. Apart from their direct mode of action against insect pests, several fungal entomopathogens have been reported as natural endophytes, paving the way for novel plant protection measures. In this study, we aimed at the selective propagation of finely dispersed Metarhizium brunneum strain BIPESCO5 mycelium in submerged culture and encapsulation in calcium alginate/starch beads to protect the fungus during drying, enable growth on different soils and promote endophytism in tomato plants. We found that a combination of osmotic pressure and increased medium viscosity promoted selective formation of finely dispersed mycelium reflected by 34.1-fold decreased pellet diameters, 1.8-fold increased mycelial biomass concentrations and low blastospore contents of 40.4 ×105 mL−1 after 48 h. Encapsulation of mycelium enhanced drying survival by 31.5%. Co-encapsulated starch was degraded by 24.8% after 21 days and served as a nutrient source for growth on soils with best results on sterile and non-sterile potting substrate with 8.7 mm and 4.4 mm radial mycelial growth, respectively, compared to water agar with 7.6 mm. When applied to the soil, encapsulation significantly increased endophytism 3.8–7.0-fold compared to plants treated with non-formulated fungal biomass. This study provides the first evidence of endophytic establishment of M. brunneum in the stem of tomato plants after application of mycelium to roots as well as on increased endophytism by encapsulation. These results might provide the basis for future work on increasing endophytism by formulation technologies

Endophytic Metarhizium brunneum mitigates nutrient deficits in potato and improves plant productivity and vitality

Krell V, Unger S, Jakobs-Schönwandt D, Patel A. Endophytic Metarhizium brunneum mitigates nutrient deficits in potato and improves plant productivity and vitality. Fungal Ecology. 2018;34:43-49.There is growing evidence that entomopathogenic fungi play a role in plant growth promotion as colonizers of internal plant tissues. However, little is known about their potential to mitigate plant abiotic stress. Here, we investigated the influence of soil fertility on Metarhizium brunneum strain CB15 endophytism levels in potato plants linked to plant productivity and vitality. By application of encapsulated M. brunneum, the endophytism level, i.e. % presence of fungus in plant tissue, increased significantly under nutrient poor conditions. This correlated with significantly improved quantum yields of photosystem II. In addition, water use efficiency was increased with higher levels of M. brunneum endophytism. Furthermore, biomass, leaf area, nitrogen and phosphorus contents were enhanced indicating fungal nutrient mobilization and transfer. Our results provide first evidence for the role of entomopathogenic fungi in mitigating nutrient deficits in soil by improving plant productivity and vitality which may increase their use in plant protection strategies

Endogenous arabitol and mannitol improve shelf life of encapsulated Metarhizium brunneum

Krell V, Jakobs-Schönwandt D, Persicke M, Patel A. Endogenous arabitol and mannitol improve shelf life of encapsulated Metarhizium brunneum. WORLD JOURNAL OF MICROBIOLOGY & BIOTECHNOLOGY. 2018;34(8): 108.Successful commercialization of microbial biocontrol agents, such as Metarhizium spp., is often constrained by poor drying survival and shelf life. Here, we hypothesized that culture age would influence endogenous arabitol, erythritol, mannitol and trehalose contents in M. brunneum mycelium and that elevated levels of these compounds would improve drying survival and shelf life of encapsulated mycelium coupled with enhanced fungal virulence against T. molitor larvae. We found that culture age significantly influenced endogenous arabitol and mannitol contents in mycelium with highest concentrations of 0.6 +/- 0.2 and 2.1 +/- 0.2 A mu g/mg after 72 h, respectively. Drying survival of encapsulated mycelium was independent of culture age and polyol content with 41.1 +/- 4.4 to 55.0 +/- 6.2%. Best shelf life was determined for biomass harvested after 72 h at all investigated storage temperatures with maximum values of 59.5 +/- 3.3% at 5 A degrees C followed by 54.5 +/- 1.6% at 18 A degrees C and 19.4 +/- 1.3% at 25 A degrees C after 6 months. Finally, high fungal virulence against T. molitor larvae of 83.3 +/- 7.6 to 98.0 +/- 1.8% was maintained during storage of encapsulated mycelium for 12 months with larval mortalities being independent of culture age and polyol content. In conclusion, our findings indicate beneficial effects of endogenous polyols in improving shelf life of encapsulated mycelium and this may spur the successful development of microbial biocontrol agents in the future

Importance of phosphorus supply through endophytic Metarhizium brunneum for root:shoot allocation and root architecture in potato plants

Krell V, Unger S, Jakobs-Schönwandt D, Patel A. Importance of phosphorus supply through endophytic Metarhizium brunneum for root:shoot allocation and root architecture in potato plants. Plant and Soil. 2018;430(1-2):87-97.Background and aims Recent studies indicate the potential of endophytic entomopathogenic fungi to promote plant growth but little is known about the responses of root architecture to fungal endophytism. This study investigates potential adaptations of root architecture upon Metarhizium brunneum endophytism linked to improved plant growth and nutrition. Methods Plants (Solanum tuberosum L.) were grown in the presence of M. brunneum applied either as nonformulated mycelium or as mycelium containing beads. After 35 days, fungal growth, root endophytism, plant biomass and nutrition as well as root attributes were determined. Results In response to endophytism promoted by bead application, plant P contents and biomass were significantly increased, while N contents and shoot allocation were also significantly increased in plants from the beads without mycelium group. Bead application resulted in a shift from fine to medium-sized roots and in an increase in the number of root forks, while root diameter, surface area and the number of root tips and crossings were independent of either bead or M. brunneum treatment. Conclusions M. brunneum containing beads supported endophytism allowing for increases in plant P contents and biomass. However, root architecture was not strongly modulated by M. brunneum endophytism with N provision through bead application being more important than fungal P delivery

Generation of Schwann cell-derived multipotent neurospheres isolated from intact sciatic nerve

Martin I, Nguyen TD, Krell V, et al. Generation of Schwann cell-derived multipotent neurospheres isolated from intact sciatic nerve. Stem Cell Reviews and Reports. 2012;8(4):1178-1187