Effect of carbon and nitrogen sources, pH and temperature on in vitro culture of several isolates of Amanita caesarea (Scop.:Fr.) Pers

An Overview of Mycorrhiza in Pines: Research, Species, and Applications

In the latest literature, climate models show that the conditions for pines, spruces, larches, and birches will deteriorate significantly. In Poland, as well as in other European countries, there are already signs of the decline of these species. This review article deals with the symbiotic relationships between fungi and plants, which can hardly be overestimated, using the example of pine trees. These are the oldest known symbiotic relationships, which are of great benefit to both components and can help plants, in particular, survive periods of severe drought and the attack of pathogens on the roots. This article describes symbioses and their causal conditions, as well as the mycorrhizal components of pine trees and their properties; characterizes ectomycorrhizal fungi and their mushroom-forming properties; and provides examples of the cultivation of pure fungal cultures, with particular attention to the specificity of the mycorrhizal structure and its effects on the growth and development of Pinus species. Finally, the role of mycorrhiza in plant protection and pathogen control is described.

Seedling ectomycorrhization is central to conifer forest restoration: a case study from Kashmir Himalaya

Over the past few decades, many countries have attempted to carry out forest landscape restoration over millions of hectares of degraded land. Such efforts, however, have met with limited success because of several factors, including a lack of adequate emphasis on ectomycorrhization of the nursery seedlings. A similar scenario is seen in the Kashmir Himalaya, where the natural regeneration of degraded forests is poor despite ample restoration efforts by forest managers. To overcome this challenge, we identified two promising ectomycorrhizal species, namely Clitocybe nuda and Cortinarius distans, for their use in ectomycorrhization of seedlings of three common conifers, namely Abies pindrow, Cedrus deodara, and Picea smithiana. Laboratory studies were carried out to investigate the requirements for optimum mycelial growth of these ectomycorrhizal fungi. Best ECM mycelial growth was obtained in the basic MMN medium containing glucose as the source of carbon and nitrogen in ammonium form. C. distans showed higher growth than C. nuda across all the treatments and also proved significantly more effective in enhancing the survival and growth of the conifer host plant seedlings. The present study resulted in standardizing the requirements for mass inoculum production of the two mycobionts which could help in successful forest restoration programmes.

Successes and challenges in the sustainable cultivation of edible mycorrhizal fungi – furthering the dream

The cultivation of edible mycorrhizal fungi (EMF) has made great progress since the first cultivation of Tuber melanosporum in 1977 but remains in its infancy. Five cultivation steps are required: (1) mycorrhizal synthesis, (2) mycorrhiza development and acclimation, (3) out-planting of mycorrhizal seedlings, (4) onset of fructification, and (5) performing tree orchards. We provide examples of successes and challenges associated with each step, including fruiting of the prestigious chanterelles in Japan recently. We highlight the challenges in establishing performing tree orchards. We report on the monitoring of two orchards established between Lactarius deliciosus (saffron milk cap) and pines in New Zealand. Saffron milk caps yields reached 0.4 and 1100 kg/ha under Pinus radiata and P. sylvestris 6 and 9 y after planting, respectively. Canopy closure began under P. radiata 7 y after planting, followed by a drastic reduction of yields, while P. sylvestris yields still hovered at 690 to 780 kg/ha after 11 y, without canopy closure. The establishment of full-scale field trials to predict yields is crucial to making the cultivation of EMF a reality in tomorrow's cropping landscape. Sustainable EMF cultivation utilizing trees in non-forested land could contribute to carbon storage, while providing revenue and other ecosystem services.

Stress tolerance of Xerocomus badius and its promotion effect on seed germination and seedling growth of annual ryegrass under salt and drought stresses

Comparative evaluations were conducted to assess the effects of different pH levels, NaCl-induced salt stress, and PEG-induced drought stress on the mycelial growth of Xerocomus badius. The results showed that X. badius mycelium grew well at a wide pH range of 5.00 ~ 9.00. Although the mycelium remained viable, mycelial growth of X. badius was significantly inhibited with increasing salt and drought stresses. Furthermore, a soilless experiment in Petri dishes was performed to investigate the potential of X. badius to induce beneficial effects on seed germination and seedling growth of annual ryegrass (Lolium multiflorum Lam.) under salt and drought stresses. Seed priming with X. badius enhanced the seedling growth of L. multiflorum Lam. under NaCl-induced salt stress and PEG-induced drought stress. However, X. badius did not significantly improve the seed germination under non-stress and mild stress conditions. It suggested that X. badius inoculation with seeds was not essential for seed germination under non-stress and mild stress conditions, but contributed highly to seedling growth under severe stress conditions. Therefore, seed priming with X. badius on ryegrass could be an effective approach to enhance plant tolerance against drought and salt stresses. X. badius could be a good candidate for the inoculation of ectomycorrhizal plants cultivation programs in mild saline and semiarid areas.

A New Report on Edible Tropical Bolete, Phlebopus spongiosus in Thailand and Its Fruiting Body Formation without the Need for a Host Plant

Phlebopus spongiosus is a well-known edible ectomycorrhizal mushroom indigenous to southern Vietnam. The mushroom specimens collected from northern Thailand in this study were identified as P. spongiosus. This identification was based on morphological characteristics and the multi-gene phylogenetic analyses. Pure cultures were isolated and the relevant suitable mycelial growth conditions were investigated. The results indicated that the fungal mycelia grew well on L-modified Melin-Norkans, and Murashige and Skoog agar all of which were adjusted to a pH of 5.0 at 30 °C. Sclerotia-like structures were observed on cultures. The ability of this mushroom to produce fruiting bodies in the absence of a host plant was determined by employing a bag cultivation method. Fungal mycelia completely covered the cultivation substrate after 90-95 days following inoculation of mushroom spawn. Under the mushroom house conditions, the highest amount of primordial formation was observed after 10-15 days at a casing with soil:vermiculite (1:1, v/v). The primordia developed into a mature stage within one week. Moreover, identification of the cultivated fruiting bodies was confirmed by both morphological and molecular methods. This is the first record of P. spongiosus found in Thailand and its ability to form fruiting bodies without a host plant.

Differences in carbon source utilisation by orchid mycorrhizal fungi from common and endangered species of Caladenia (Orchidaceae)

Terrestrial orchids depend on orchid mycorrhizal fungi (OMF) as symbionts for their survival, growth and nutrition. The ability of OMF from endangered orchid species to compete for available resources with OMF from common species may affect the distribution, abundance and therefore conservation status of their orchid hosts. Eight symbiotically effective OMF from endangered and more common Caladenia species were tested for their ability to utilise complex insoluble and simple soluble carbon sources produced during litter degradation by growth with different carbon sources in liquid medium to measure the degree of OMF variation with host conservation status or taxonomy. On simple carbon sources, fungal growth was assessed by biomass. On insoluble substrates, ergosterol content was assessed using ultra-performance liquid chromatography (UPLC). The OMF grew on all natural materials and complex carbon sources, but produced the greatest biomass on xylan and starch and the least on bark and chitin. On simple carbon sources, the greatest OMF biomass was measured on most hexoses and disaccharides and the least on galactose and arabinose. Only some OMF used sucrose, the most common sugar in green plants, with possible implications for symbiosis. OMF from common orchids produced more ergosterol and biomass than those from endangered orchids in the Dilatata and Reticulata groups but not in the Patersonii and Finger orchids. This suggests that differences in carbon source utilisation may contribute to differences in the distribution of some orchids, if these differences are retained on site.

Favourable culture conditions for mycelial growth of Hydnum repandum, a medicinal mushroom

In this study, factors such as pH, temperature, carbon and nitrogen sources that affect mycelial growth of Hydnum repandum, a medicinal mushroom, were investigated. Different inoculum media for vegetative inoculum production were also examined. The best suitable pH for mycelial growth was found to be 5.5. Among constant temperatures, the best mycelial growth was obtained at 20 and 25°C. The mycelial growth drastically decreased at 15°C, and no mycelia were obtained at 30°C. Glucose and mannitol were found to be the most suitable carbon sources. Ca(NO3)2 as a nitrogen source gave the best results for mycelial growth. The poorest mycelial growth was noted in sucrose and xylose as carbon sources and in NH4NO3 and (NH4)2HPO4 as nitrogen sources. Peat and peat: vermiculite mixtures (1:4, 1:6, 1:8 and 1:10, v:v) were the best media to use in producing the vegetative inoculum of H. repandum.

Biotrophic transportome in mutualistic plant-fungal interactions

Understanding the mechanisms that underlie nutrient use efficiency and carbon allocation along with mycorrhizal interactions is critical for managing croplands and forests soundly. Indeed, nutrient availability, uptake and exchange in biotrophic interactions drive plant growth and modulate biomass allocation. These parameters are crucial for plant yield, a major issue in the context of high biomass production. Transport processes across the polarized membrane interfaces are of major importance in the functioning of the established mycorrhizal association as the symbiotic relationship is based on a 'fair trade' between the fungus and the host plant. Nutrient and/or metabolite uptake and exchanges, at biotrophic interfaces, are controlled by membrane transporters whose regulation patterns are essential for determining the outcome of plant-fungus interactions and adapting to changes in soil nutrient quantity and/or quality. In the present review, we summarize the current state of the art regarding transport systems in the two major forms of mycorrhiza, namely ecto- and arbuscular mycorrhiza.

In vitro mycorrhization and acclimatization of Amanita caesareoides and its relatives on Pinus densiflora

Amanita caesareoides is a sister species of Amanita caesarea, also known as Caesar's mushroom and one of the most desirable edible mycorrhizal mushrooms. However, cultivation of Caesar's mushrooms has not yet been successful due to the difficulties involved in establishing pure cultures. In this study, we established pure cultures of four Asian Caesar's mushroom species, i.e., A. caesareoides, Amanita javanica, Amanita esculenta, and Amanita similis, which were identified by sequence analysis of their rDNA internal transcribed spacer (ITS) region. Five selected isolates in A. caesareoides, A. javanica, and A. esculenta were tested for ectomycorrhizal syntheses with axenic Pinus densiflora seedlings in vitro. Ectomycorrhizal tips of each fungal isolate tested were observed on pine lateral roots within 5 months of inoculation. Seventeen pine seedlings that formed ectomycorrhizas in vitro with these three Amanita species were acclimatized under non-sterile conditions. Seven months following acclimatization, ectomycorrhizal colonization by A. caesareoides was observed on newly grown root tips, which was confirmed by polymerase chain reaction restriction fragment length polymorphism analysis of the fungal rDNA ITS region. Two other Amanita species also survived during ectomycorrhizal acclimatization. These results suggest that the cultivation of A. caesareoides and its relatives can be attempted through mycorrhizal synthesis using P. densiflora as a host. This is the first report of in vitro mycorrhization of Asian Caesar's mushrooms and their acclimatization under non-sterile conditions.

Antioxidant Activity of Aspergillus fumigatus

The antioxidant activity of Aspergillus fumigatus was assayed by different procedures and correlated with its extracellular total phenolic contents. Different physio-chemical parameters were optimized to enhance the activity. The culture grown under stationary conditions for 10 days at 25°C at pH 7 gave the best antioxidant activity. Statistical approaches demonstrated sucrose and NaNO(3) to be the most suitable carbon and nitrogen sources, respectively. Response surface analysis showed 5% sucrose, 0.05% NaNO(3), and incubation temperature of 35°C to be the optimal conditions for best expression of antioxidant activity. Under these conditions, the antioxidant potential assayed through different procedures was 89.8%, 70.1%, and 70.2% scavenging effect for DPPH radical, ferrous ion and nitric oxide ion, respectively. The reducing power showed an absorbance of 1.0 and FRAP assay revealed the activity of 60.5%. Extracellular total phenolic content and antioxidant activity as assayed by different procedures positively correlated.