First Report of Lecanicillium aphanocladii causing rot of Morchella sextelata in China

Dynamics of the soil microbial community associated with Morchella cultivation: diversity, assembly mechanism and yield prediction

Introduction

The artificial cultivation of morels has been a global research focus owing to production variability. Understanding the microbial ecology in cultivated soil is essential to increase morel yield and alleviate pathogen harm.

Methods

A total of nine Morchella cultivation experiments in four soil field types, forest, paddy, greenhouse, and orchard in Shanghai city were performed to determine the potential ecological relationship between Morchella growth and soil microbial ecology.

Results

Generally, significant variation was observed in the soil microbial diversity and composition between the different experimental field types. The niche width analysis indicated that the bacterial habitat niche breadth was significantly greater than the fungal community width, which was further confirmed by a null model that revealed that homogeneous selection could explain 46.26 and 53.64% of the variance in the bacterial and fungal assemblies, respectively. Moreover, the neutral community model revealed that stochastic processes dominate the bacterial community in forests and paddies and both the bacterial and fungal communities in orchard crops, whereas deterministic processes mostly govern the fungal community in forests and paddies and both the bacterial and the fungal communities in greenhouses. Furthermore, co-occurrence patterns were constructed, and the results demonstrated that the dynamics of the soil microbial community are related to fluctuations in soil physicochemical characteristics, especially soil potassium. Importantly, structural equation modeling further demonstrated that the experimental soil type significantly affects the potassium content of the soil, which can directly or indirectly promote Morchella yield by inhibiting soil fungal richness.

Discussion

This was the first study to predict morel yield through soil potassium fertilizer and soil fungal community richness, which provides new insights into deciphering the importance of microbial ecology in morel agroecosystems.

Large-Scale Field Cultivation of Morchella and Relevance of Basic Knowledge for Its Steady Production

Morels are one of the most highly prized edible and medicinal mushrooms worldwide. Therefore, historically, there has been a large international interest in their cultivation. Numerous ecological, physiological, genetic, taxonomic, and mycochemical studies have been previously developed. At the beginning of this century, China finally achieved artificial cultivation and started a high-scale commercial development in 2012. Due to its international interest, its cultivation scale and area expanded rapidly in this country. However, along with the massive industrial scale, a number of challenges, including the maintenance of steady economic profits, arise. In order to contribute to the solution of these challenges, formal research studying selection, species recognition, strain aging, mating type structure, life cycle, nutrient metabolism, growth and development, and multi-omics has recently been boosted. This paper focuses on discussing current morel cultivation technologies, the industrial status of cultivation in China, and the relevance of basic biological research, including, e.g., the study of strain characteristics, species breeding, mating type structure, and microbial interactions. The main challenges related to the morel cultivation industry on a large scale are also analyzed. It is expected that this review will promote a steady global development of the morel industry based on permanent and robust basic scientific knowledge.

Characterization and Genome Analysis of Cladobotryum mycophilum, the Causal Agent of Cobweb Disease of Morchella sextelata in China

Cobweb disease is a fungal disease that can cause serious damage to edible mushrooms worldwide. To investigate cobweb disease in Morchella sextelata in Guizhou Province, China, we isolated and purified the pathogen responsible for the disease. Through morphological and molecular identification and pathogenicity testing on infected M. sextelata, we identified Cladobotryum mycophilum as the cause of cobweb disease in this region. This is the first known occurrence of this pathogen causing cobweb disease in M. sextelata anywhere in the world. We then obtained the genome of C. mycophilum BJWN07 using the HiFi sequencing platform, resulting in a high-quality genome assembly with a size of 38.56 Mb, 10 contigs, and a GC content of 47.84%. We annotated 8428 protein-coding genes in the genome, including many secreted proteins, host interaction-related genes, and carbohydrate-active enzymes (CAZymes) related to the pathogenesis of the disease. Our findings shed new light on the pathogenesis of C. mycophilum and provide a theoretical basis for developing potential prevention and control strategies for cobweb disease.

Transcriptomic and Metabolomic Profiles Provide Insights into the Red-Stipe Symptom of Morel Fruiting Bodies

The cultivation of true morels (Morchella spp., Morchellaceae, Ascomycota) has rapidly expanded in recent years, especially in China. Red stipe is a symptom wherein the stipe of morel fruiting bodies becomes red-gray, resulting in the gradual death of the affected fruiting bodies. The impact of red-stipe symptom occurrence on the development and nutritional quality of morel fruiting bodies remains unclear. Herein, morel ascocarps with the red-stipe symptom (R) and normal (N), artificially cultivated in the Fujian Province of China, were selected for the transcriptome and metabolome analysis to study the physiological and biochemical responses of morel fruiting bodies to the red-stipe symptom. Transcriptome data revealed several differentially expressed genes between the R and N groups significantly enriched in the tyrosine, riboflavin, and glycerophospholipid metabolism pathways. Similarly, the differentially accumulated metabolites were mainly assigned to metabolic pathways, including tyrosine, the biosynthesis of plant secondary metabolites, and the biosynthesis of amino acids. Moreover, the transcriptome and metabolome data combination revealed that tyrosine metabolism was the most enriched pathway, which was followed by ATP-binding cassette (ABC) transport, alanine, aspartate, and glutamate metabolism. Overall, the integration of transcriptomic and metabolomic data of M. sextelata affected by red-stipe symptoms identified several important genes, metabolites, and pathways. These findings further improve our understanding of the mechanisms underlying the red-stipe symptom development of M. sextelata and provide new insights into how to optimize its cultivation methods.

Epidemic Identification of Fungal Diseases in Morchella Cultivation across China

True morels (Morchella, Pezizales) are world-renowned edible mushrooms (ascocarps) that are widely demanded in international markets. Morchella has been successfully artificially cultivated since 2012 in China and is rapidly becoming a new edible mushroom industry occupying up to 16,466 hectares in the 2021-2022 season. However, nearly 25% of the total cultivation area has annually suffered from fungal diseases. While a variety of morel pathogenic fungi have been reported their epidemic characteristics are unknown, particularly in regional or national scales. In this paper, ITS amplicon sequencing and microscopic examination were concurrently performed on the morel ascocarp lesions from 32 sites in 18 provinces across China. Results showed that Diploöspora longispora (75.48%), Clonostachys solani (5.04%), Mortierella gamsii (0.83%), Mortierella amoeboidea (0.37%) and Penicillium kongii (0.15%) were the putative pathogenic fungi. The long, oval, septate conidia of D. longispora was observed on all ascocarps. Oval asexual spores and sporogenic structures, such as those of Clonostachys, were also detected in C. solani infected samples with high ITS read abundance. Seven isolates of D. longispora were isolated from seven selected ascocarps lesions. The microscopic characteristics of pure cultures of these isolates were consistent with the morphological characteristics of ascocarps lesions. Diploöspora longispora had the highest amplification abundance in 93.75% of the samples, while C. solani had the highest amplification abundance in six biological samples (6.25%) of the remaining two sampling sites. The results demonstrate that D. longispora is a major culprit of morel fungal diseases. Other low-abundance non-host fungi appear to be saprophytic fungi infecting after D. longispora. This study provides data supporting the morphological and molecular identification and prevention of fungal diseases of morel ascocarps.