Compost Filling Methods Affect Green Mold Disease Incidence in Commercial Mushrooms

Green mold (Trichoderma aggressivum) is an invasive disease of commercial mushrooms introduced into the United States from Europe that now has spread to commercial mushrooms throughout North America. We examined potential sources of invasive green mold inoculum and the association with different compost filling technologies on a large actively producing commercial mushroom farm. Green mold foci were sampled bed by bed, which generated 20,906 data points. Logistic regression was used to determine treatment differences. Mechanical filling of compost into the beds reduced green mold incidence over hand filling, apparently due to the reduced incidence of worker contact with the floor and between beds. Lower growing beds located closer to the floor had a higher incidence of green mold for both mechanical and hand-filled beds. We conclude that mechanical filling and generally reducing contact with the floor and between beds will reduce spread of green mold in commercial mushroom production.

Diversity of Trichoderma species associated with green mold contaminating substrates of Lentinula edodes and their interaction

Introduction

The contamination of Trichoderma species causing green mold in substrates poses a significant obstacle to the global production of Lentinula edodes, adversely impacting both yield and quality of fruiting bodies. However, the diversity of Trichoderma species in the contaminated substrates of L. edodes (CSL) in China is not clear. The purpose of this study was to assess the biodiversity of Trichoderma species in CSL, and their interactions with L. edodes.

Methods

A comprehensive two-year investigation of the biodiversity of Trichoderma species in CSL was conducted with 150 samples collected from four provinces of China. Trichoderma strains were isolated and identified based on integrated studies of phenotypic and molecular data. Resistance of L. edodes to the dominant Trichoderma species was evaluated in dual culture in vitro.

Results

A total of 90 isolates were obtained and identified as 14 different Trichoderma species, including six new species named as Trichoderma caespitosus, T. macrochlamydospora, T. notatum, T. pingquanense, T. subvermifimicola, and T. tongzhouense, among which, T. atroviride, T. macrochlamydospora and T. subvermifimicola were identified as dominant species in the CSL. Meanwhile, three known species, namely, T. auriculariae, T. paraviridescens and T. subviride were isolated from CSL for the first time in the world, and T. paratroviride was firstly reported to be associated with L. edodes in China. Notebly, the in vitro evaluation of L. edodes resistance to dominant Trichoderma species showed strains of L. edodes generally possess poor resistance to Trichoderma contamination with L. edodes strain SX8 relatively higher resistant.

Discussion

This study systematically investigated the diversity of Trichoderma species in the contaminated substrate of L. edodes, and a total of 31 species so far have been reported, indicating that green mold contaminated substrates of edible fungi were undoubtedly a biodiversity hotspot of Trichoderma species. Results in this study will provide deeper insight into the genus Trichoderma and lay a strong foundation for scientific management of the Trichoderma contamination in L. edodes cultivation.

Application of Thymol Vapors to Control Postharvest Decay Caused by Penicillium digitatum and Lasiodiplodia theobromae in Grapefruit

Two of the major postharvest diseases impacting grapefruit shelf life and marketability in the state of Florida (USA) are stem-end rot (SER) caused by Lasiodiplodia theobromae and green mold (GM) caused by Penicillium digitatum. Here, we investigated the in vitro and in vivo efficacy of vapors of thymol, a natural compound found in the essential oil of various plants and the primary constituent of thyme (Thymus vulgaris) oil, as a potential solution for the management of GM and SER. Thymol vapors at concentrations lower than 10 mg L-1 significantly inhibited the mycelial growth of both pathogens, causing severe ultrastructural damage to P. digitatum conidia. In in vivo trials, the incidence and lesion area of GM and SER on inoculated grapefruit were significantly reduced after a 5 d exposure to 50 mg L-1 thymol vapors. In addition, the in vitro and in vivo sporulation of P. digitatum was suppressed by thymol. When applied in its vapor phase, thymol had no negative effect on the fruit, neither introducing perceivable off-flavor nor causing additional weight loss. Our findings support the pursuit of further studies on the use of thymol, recognized as safe for human health and the environment, as a promising strategy for grapefruit postharvest disease management.

The Biological Action and Structural Characterization of Eryngitin 3 and 4, Ribotoxin-like Proteins from Pleurotus eryngii Fruiting Bodies

Ribotoxin-like proteins (RL-Ps) are specific ribonucleases found in mushrooms that are able to cleave a single phosphodiester bond located in the sarcin-ricin loop (SRL) of the large rRNA. The cleaved SRL interacts differently with some ribosomal proteins (P-stalk). This action blocks protein synthesis because the damaged ribosomes are unable to interact with elongation factors. Here, the amino acid sequences of eryngitin 3 and 4, RL-Ps isolated from Pleurotus eryngii fruiting bodies, were determined to (i) obtain structural information on this specific ribonuclease family from edible mushrooms and (ii) explore the structural determinants which justify their different biological and antipathogenic activities. Indeed, eryngitin 3 exhibited higher toxicity with respect to eryngitin 4 against tumoral cell lines and model fungi. Structurally, eryngitin 3 and 4 consist of 132 amino acids, most of them identical and exhibiting a single free cysteinyl residue. The amino acidic differences between the two toxins are (i) an additional phenylalanyl residue at the N-terminus of eryngitin 3, not retrieved in eryngitin 4, and (ii) an additional arginyl residue at the C-terminus of eryngitin 4, not retrieved in eryngitin 3. The 3D models of eryngitins show slight differences at the N- and C-terminal regions. In particular, the positive electrostatic surface at the C-terminal of eryngitin 4 is due to the additional arginyl residue not retrieved in eryngitin 3. This additional positive charge could interfere with the binding to the SRL (substrate) or with some ribosomal proteins (P-stalk structure) during substrate recognition.

Molecular Approaches for Detection of Trichoderma Green Mold Disease in Edible Mushroom Production

Due to the evident aggressive nature of green mold and the consequently huge economic damage it causes for producers of edible mushrooms, there is an urgent need for prevention and infection control measures, which should be based on the early detection of various Trichoderma spp. as green mold causative agents. The most promising current diagnostic tools are based on molecular methods, although additional optimization for real-time, in-field detection is still required. In the first part of this review, we briefly discuss cultivation-based methods and continue with the secondary metabolite-based methods. Furthermore, we present an overview of the commonly used molecular methods for Trichoderma species/strain detection. Additionally, we also comment on the potential of genomic approaches for green mold detection. In the last part, we discuss fast screening molecular methods for the early detection of Trichoderma infestation with the potential for in-field, point-of-need (PON) application, focusing on isothermal amplification methods. Finally, current challenges and future perspectives in Trichoderma diagnostics are summarized in the conclusions.

Application of New Conformal Cooling Layouts to the Green Injection Molding of Complex Slender Polymeric Parts with High Dimensional Specifications

Eliminating warpage in injection molded polymeric parts is one of the most important problems in the injection molding industry today. This situation is critical in geometries that are particularly susceptible to warping due to their geometric features, and this occurs with topologies of great length and slenderness with high changes in thickness. These features are, in these special geometries, impossible to manufacture with traditional technologies to meet the dimensional and sustainable requirements of the industry. This paper presents an innovative green conformal cooling system that is specifically designed for parts with slender geometric shapes that are highly susceptible to warping. Additionally, the work presented by the authors investigates the importance of using highly conductive inserts made of steel alloys in combination with the use of additively manufactured conformal channels for reducing influential parameters, such as warpage, cooling time, and residual stresses in the complex manufacturing of long and slender parts. The results of this real industrial case study indicated that the use of conformal cooling layouts decreased the cycle time by 175.1 s-66% below the current cooling time; the temperature gradient by 78.5%-specifically, 18.16 °C; the residual stress by 39.78 MPa-or 81.88%; and the warpage by 6.9 mm-or 90.5%. In this way, it was possible to achieve a final warping in the complex geometry studied of 0.72 mm, which was under the maximum value required at the industrial level of 1 mm. The resulting values obtained by the researchers present a turning point from which the manufacturing and sustainability in the injection molding of said plastic geometries is possible, and they take into account that the geometric manufacturing features analyzed will present a great demand in the coming years in the auto parts manufacturing industry.

Transcriptome analysis of Ganoderma lingzhi (Agaricomycetes) response to Trichoderma hengshanicum infection

Green mold caused by Trichoderma spp. has become one of the most serious diseases which threatening the production of Ganoderma lingzhi. To understand the possible resistance mechanism of the G. lingzhi response to T. hengshanicum infection, we examined the G. lingzhi transcript accumulation at 0, 12, and 24 h after T. hengshanicum inoculation. The gene expression analysis was conducted on the interaction between G. lingzhi and T. hengshanicum using RNA-seq and digital gene expression (DGE) profiling methods. Transcriptome sequencing indicated that there were 162 differentially expressed genes (DEGs) at three infection time points, containing 15 up-regulated DEGs and 147 down-regulated DEGs. Resistance-related genes thaumatin-like proteins (TLPs) (PR-5s), phenylalanine ammonia-lyase, and Beta-1,3-glucan binding protein were significantly up-regulated. At the three time points of infection, the heat shock proteins (HSPs) genes of G. lingzhi were down-regulated. The down-regulation of HSPs genes led to the inhibition of HSP function, which may compromise the HSP-mediated defense signaling transduction pathway, leading to G. lingzhi susceptibility. Pathway enrichment analyses showed that the main enriched pathways by G. lingzhi after infection were sphingolipid metabolism, ether lipid metabolism, and valine, leucine and isoleucine degradation pathway. Overall, the results described here improve fundamental knowledge of molecular responses to G. lingzhi defense and contribute to the design of strategies against Trichoderma spp.

The Role of ABA in the Interaction between Citrus Fruit and Penicillium digitatum

Abscisic acid (ABA) protects citrus fruit against Penicillium digitatum infection. The global mechanisms involved in the role of ABA in the P. digitatum-citrus fruit interaction are unknown. Here, we determine the transcriptome differences between the Navelate (Citrus sinensis (L.) Osbeck) orange and its ABA-deficient mutant Pinalate, which is less resistant to infection. Low ABA levels may affect both the constitutive mechanisms that protect citrus fruit against P. digitatum and early responses to infection. The repression of terpenoid, phenylpropanoid and glutation metabolism; of oxidation-reduction processes; and of processes related to the defense response to fungus and plant hormone signal transduction may be one part of the constitutive defense reduced in the mutant against P. digitatum. Our results also provide potential targets for developing P. digitatum-citrus fruit-resistant varieties. Of those up-regulated by ABA, a thaumatin protein and a bifunctional inhibitor/LTP, which are relevant in plant immunity, were particularly remarkable. It is also worth highlighting chlorophyllase 1 (CLH1), induced by infection in Pinalate, and the OXS3 gene, which was down-regulated by ABA, because the absence of OXS3 activates ABA-responsive genes in plants.

First report of green mold disease caused by Penicillium citrinum on Dictyophora rubrovalvata in China

Dictyophora rubrovolvata is a saprophytic mushroom widely cultivated in China, including Guizhou Province for its high nutritional, medicinal, and economical values (Chen et al. 2021). In May 2021, green mold disease was observed on the fruiting bodies of D. rubrovolvata, causing its death or preventing it from forming a sporocarp, in an indoor-production facility at Asuo village, Baiyun District Guiyang city, Guizhou Province, China (26°73'51" N, 106°72'88" E). The disease incidence was 60%-70% in the affected 1.33-ha growing area, causing a serious economic loss. To identify the causal agent, a total of 15 samples with symptomatic symptoms were collected. Small pieces (5 mm × 5 mm) were cut from the diseased tissues, surface sterilized in 0.4% NaClO for 5 min, washed three times with sterilized water, placed on potato dextrose agar (PDA) medium, and incubated at 24 °C for 7 days. Twenty-one pure cultures were obtained by single-spore isolation method. The colonies were initially white but after seven days as conidia developed they turned green. Hyphae were hyaline and guttulate. Conidiophores were verrucose stipes, triverticulate, and phialides flask shaped. Conidia were smooth and pale green, with subglobose to globose shape measuring 2.0-2.5 × 1.8-2.5 µm (n=50). Based on these morphological characteristics, the isolates matched the description of the genus Penicillium (Visagie et al. 2014). To confirm the identity, DNA of five representative isolates (QS001, QS005, QS008, QS015, QS017) was extracted according to the manufacturer's instructions (Biomiga Fungal DNA Extraction Kit; CA, USA). Afterwards, PCR was performed to amplify ITS region, calmodulin and β-tubulin genes using primer pairs ITS1/ITS4 (White et al. 1990), CMD5/CMD6 (Glass et al. 1995), and Bt2a/Bt2b (Hong et al. 2006), respectively. BLASTN analysis of these sequences showed the best matches with Penicillium citrinum CBS 139.45 (ITS region: 98.60% (493/500 bp) identity to accession MH856132.1; CMD: 99.79% (469/470 bp) identity to accession MN969245.1; β-tubulin:100% (407/407 bp) identity to accession GU944545.1). Representative sequences of the sequenced DNA regions were deposited in GenBank (ITS region: OK446552; CMD: OK492612; β-tubulin: OK482677). Furthermore, a phylogenetic tree was constructed with MEGA 7 based on the concatenated sequences. Koch's postulates were met to confirm the pathogenicity of the representative isolate (QS001) on D. rubrovolvata. Six discs (5mm×5mm) from actively growing P. citrinum QS001 colonies (5-day-old) were placed on six fruiting bodies of D. rubrovolvata (5-month-old). Mock inoculations were performed using PDA discs only without any fungus. The inoculation sites were wrapped with a sterilized 200-μm nylon mesh. All fruiting bodies were incubated at 23°C ± 2°C under a 0-h/24-h photoperiod and 80% relative humidity (RH) after inoculation. After 14 days, green mold was observed on all P. citrinum QS001 inoculated mushrooms. In contrast, no disease was observed in mock inoculated group. The disease assays were repeated three times. P. citrinum QS001 was isolated from all inoculated D. rubrovolvata and verified via the molecular analysis mentioned above. To the best of our knowledge, this is the first report that P. citrinum causes green mold on D. rubrovalvata in China and further studies should focus on managing this disease to prevent any disease outbreaks.

Albedo- and Flavedo-Specific Transcriptome Profiling Related to Penicillium digitatum Infection in Citrus Fruit

Penicillium digitatum is the main postharvest pathogen of citrus fruit. Although the inner fruit peel part (albedo) is less resistant than the outer part (flavedo) to P. digitatum, the global mechanisms involved in their different susceptibility remain unknown. Here, we examine transcriptome differences between both tissues at fruit harvest and in their early responses to infection. At harvest, not only was secondary metabolism, involving phenylpropanoids, waxes, and terpenoids, generally induced in flavedo vs. albedo, but also energy metabolism, transcription factors (TFs), and biotic stress-related hormones and proteins too. Flavedo-specific induced responses to infection might be regulated in part by ERF1 TF, and are related to structural plant cell wall reinforcement. Other induced responses may be related to H₂O₂, the synthesis of phenylpropanoids, and the stress-related proteins required to maintain basal defense responses against virulent pathogens, whereas P. digitatum represses some hydrolase-encoding genes that play different functions and auxin-responsive genes in this peel tissue. In infected albedo, the repression of transport and signal transduction prevail, as does the induction of not only the processes related to the synthesis of flavonoids, indole glucosinolates, cutin, and oxylipins, but also the specific genes that elicit plant immunity against pathogens.

Preharvest and Postharvest Applications of a Pomegranate Peel Extract to Control Citrus Fruit Decay During Storage and Shelf Life

Green and blue molds are the most important postharvest diseases affecting citrus in storage. These diseases are commonly controlled with fungicides, but legislative restrictions, consumer concerns, and the development of resistant strains of the pathogens have increasingly led to the search for alternative methods of control. A pomegranate peel extract (PGE) was very effective in controlling Valencia orange and clementine postharvest rot under commercial conditions. After cold storage and 7 days of shelf life, the incidence of decay on oranges sprayed before harvest with PGE at 12, 6, and 3 g/liter was reduced by 78.9, 76.0, and 64.6%, respectively. Similarly, postharvest dipping treatments with PGE reduced rot by 90.2, 84.3, and 77.6%, respectively. Comparable levels of protection were also achieved on clementines. On both oranges and clementines, the extract provided a significantly higher level of protection compared with imazalil, a fungicide commonly used for postharvest treatments. The high level of efficacy and the consistent results on different fruit species (clementines and oranges) and with different application methods (preharvest and postharvest) were evidence of reliability and flexibility. PGE also showed a strong antimicrobial activity against fungi and bacteria, suggesting its possible use in sanitizers to reduce the microbial contamination of recirculated water in packinghouses. The results of the present study encourage the integration of conventional chemical fungicides and sanitizers with PGE to control citrus postharvest rot.

Control of Fungal Diseases in Mushroom Crops while Dealing with Fungicide Resistance: A Review

Mycoparasites cause heavy losses in commercial mushroom farms worldwide. The negative impact of fungal diseases such as dry bubble (Lecanicillium fungicola), cobweb (Cladobotryum spp.), wet bubble (Mycogone perniciosa), and green mold (Trichoderma spp.) constrains yield and harvest quality while reducing the cropping surface or damaging basidiomes. Currently, in order to fight fungal diseases, preventive measurements consist of applying intensive cleaning during cropping and by the end of the crop cycle, together with the application of selective active substances with proved fungicidal action. Notwithstanding the foregoing, the redundant application of the same fungicides has been conducted to the occurrence of resistant strains, hence, reviewing reported evidence of resistance occurrence and introducing unconventional treatments is worthy to pave the way towards the design of integrated disease management (IDM) programs. This work reviews aspects concerning chemical control, reduced sensitivity to fungicides, and additional control methods, including genomic resources for data mining, to cope with mycoparasites in the mushroom industry.

Alternative Management Approaches of Citrus Diseases Caused by Penicillium digitatum (Green Mold) and Penicillium italicum (Blue Mold)

Green mold (Penicillium digitatum) and blue mold (Penicillium italicum) are among the most economically impactful post-harvest diseases of citrus fruit worldwide. Post-harvest citrus diseases are largely controlled with synthetic fungicides such as pyrimethanil, imazalil, fludioxonil, and thiabendazole. Due to their toxic effects, prolonged and excessive application of these fungicides is gradually restricted in favor of safe and more eco-friendly alternatives. This review comprehensively describes alternative methods for the control of P. digitatum and P. italicum: (a) antagonistic micro-organisms, (b) plant extracts and essential oils, (c) biofungicides, (d) chitosan and chitosan-based citrus coatings, (e) heat treatments, (f) ionizing and non-ionizing irradiations, (g) food additives, and (h) synthetic elicitors. Integrating multiple approaches such as the application of biocontrol agents with food additives or heat treatments have overcome some drawbacks to single treatments. In addition, integrating treatment approaches could produce an additive or synergistic effect on controlling both molds for a satisfactory level of disease reduction in post-harvest citrus. Further research is warranted on plant resistance and fruit-pathogen interactions to develop safer strategies for the sustainable control of P. digitatum and P. italicum in citrus.

Molecular Markers for Detecting a Wide Range of Trichoderma spp. that Might Potentially Cause Green Mold in Pleurotus eryngii

In Pleurotus sp., green mold, which is considered a major epidemic, is caused by several Trichoderma species. To develop a rapid molecular marker specific for Trichoderma spp. that potentially cause green mold, eleven Trichoderma species were collected from mushroom farms and the Korean Agricultural Culture Collection (KACC). A dominant fungal isolate from a green mold-infected substrate was identified as Trichoderma pleuroticola based on the sequences of its internal transcribed spacer (ITS) and translation elongation factor 1-α (tef1) genes. In artificial inoculation tests, all Trichoderma spp., including T. atroviride, T. cf. virens, T. citrinoviride, T. harzianum, T. koningii, T. longibrachiatum, T. pleurotum, and T. pleuroticola, showed pathogenicity to some extent, and the observed symptoms were soaked mycelia with a red-brown pigment and retarded mycelium regeneration. A molecular marker was developed for the rapid detection of wide range of Trichoderma spp. based on the DNA sequence alignment of the ITS1 and ITS2 regions of Trichoderma spp. The developed primer set detected only Trichoderma spp., and no cross reactivity with edible mushrooms was observed. The detection limits for the PCR assay of T. harzianum (KACC40558), T. pleurotum (KACC44537), and T. pleuroticola (CAF-TP3) were found to be 500, 50, and 5 fg, respectively, and the detection limit for the pathogen-to-host ratio was approximately 1:10,000 (wt/wt).

Biocontrol ability and action mechanisms of Aureobasidium pullulans GE17 and Meyerozyma guilliermondii KL3 against Penicillium digitatum DSM2750 and Penicillium expansum DSM62841 causing postharvest diseases

Epiphytic yeasts were isolated from different cultivars of apples and lemons and identified by a combination of PCR-RFLP of 5.8S rRNA region and sequencing of D1/D2 domain of the 26S rRNA gene. Among 69 isolates, Aureobasidium pullulans GE17 and Meyerozyma guilliermondii KL3 strains showed the greatest antagonistic activity against two significant apple and lemon postharvest pathogens, Penicillium expansum DSM62841 (blue mold) and Penicillium digitatum DSM2750 (green mold), after preliminary screening. Yeasts were applied as single and mixed cultures with two different cell concentrations of 10⁶ and 10⁸ cells/ml in the present study. It was determined that antagonistic activity of two yeast strains studied emerged with a combination of several mechanisms of action including competition for space and nutrients, production of volatile organic compounds (VOCs), secretion of extracellular lytic enzymes and inhibition of fungal spore germination. The highest inhibition of mycelial growth on P. expansum DSM62841 and P. digitatum DSM2750 (83.4% and 74.7%, respectively) was achieved by utilization of single culture of A. pullulans GE17. Otherwise, the application of mixed culture at the ratio of 10⁸ cells/ml inhibited spore germination of both pathogens from 86% to 95%. Results of this study suggest that an increase in yeast cell concentrations positively affected their biocontrol activity against blue and green molds. According to the results, employing single culture of M. guilliermondii KL3 did not exhibit effective antagonistic activity against blue and green molds. However, utilization of A. pullulans GE17 alone and mixed culture showed succesfull controlling against both P. expansum DSM62841 and P. digitatum DSM2750.

UHPLC-Q-TOF/MS-Based Metabolomics Approach Reveals the Antifungal Potential of Pinocembroside against Citrus Green Mold Phytopathogen

Pinocembroside (PiCB) isolated from Ficus hirta Vahl. fruit was studied herein with the aim to find the potential mechanism for significant inhibition of growth of Penicillium digitatum, a causative pathogen of citrus green mold disease. PiCB substantially inhibited mycelial growth of P. digitatum, with the observed half maximal effective concentration (EC50), minimum inhibitory concentration (MIC), and minimum fungicidal concentration (MFC) of 120.3, 200, and 400 mg/L, respectively. Moreover, PiCB altered hyphal morphology and cellular morphology by breaking and shrinking of mycelia, decomposing cell walls, cytoplasmic inclusions. In addition to, a non-targeted metabolomics analysis by UHPLC-Q-TOF/MS was also performed, which revealed that PiCB treatment notably disrupted the metabolisms of amino acids, lipids, fatty acids, TCA, and ribonucleic acids, thereby contributing to membrane peroxidation. Current findings provide a new perception into the antifungal mechanism of PiCB treatment in inhibiting P. digitatum growth through membrane peroxidation.

Effect of NaHCO3 treatments on the activity of cell-wall-degrading enzymes produced by Penicillium digitatum during the pathogenesis process on grapefruit

BACKGROUND

This study was performed to clarify the strategies of Penicillium digitatum during pathogenesis on citrus, assessing, on albedo plugs, the effects of treatment with sodium bicarbonate (NaHCO₃ ), at two different pH values (5 and 8.3), on cell-wall-degrading enzyme activity over a period of 72 h.

RESULTS

Treatment with NaHCO₃ , under alkaline pH, delayed the polygalacturonase activity for 72 h, or 48 h in the case of the pectin lyase, compared with the control or the same treatment at pH 5. In contrast, pectin methyl esterase activity rapidly increased after 24 h, in plugs dipped in the same solution. In this case, the activity remained higher than untreated or pH 5-treated plugs up to 72 h.

CONCLUSION

The rapid increase in pectin methyl esterase activity under alkaline conditions is presumably the strategy of the pathogen to lower the pH, soon after the initiation of infection, in order to restore an optimal environment for the subsequent polygalacturonase and pectin lyase action. In fact, at the same time, a low pH delayed the enzymatic activity of polygalacturonase and pectin lyase, the two enzymes that actually cleave the α-1,4-linkages between the galacturonic acid residues. © 2018 Society of Chemical Industry.

Diversity and effect of Trichoderma spp. associated with green mold disease on Lentinula edodes in China

Lentinula edodes, one of the most important edible mushrooms in China, is affected heavily by the infection of green mold that overgrows mushroom mycelia. We collected the diseased samples from main L. edodes cultivation regions in China to characterize the pathogen and to study the effect of Trichoderma spp. on L. edodes species. We identified six Trichoderma species, that is, T. harzianum, T. atroviride, T. viride, T. pleuroticola, T. longibrachiatum, and T. oblongisporum based on the internal transcribed spacer or tef1-α sequences and morphology characteristics. In confrontation cultures on Petri plates or in tubes, and in L. edodes cultures in a medium containing Trichoderma metabolites, L. edodes mycelia were not only distorted and swollen, but also inhibited by Trichoderma isolates. It is not possible that adjusting pH value or temperature is used for controlling L. edodes green disease, because the growth of most of Trichoderma isolates and L. edodes shared similar pH and temperature conditions.

Quantification of the Toxicity of Aqueous Chlorine to Spores of Penicillium digitatum and Geotrichum citri-aurantii

Chlorine toxicity to Penicillium digitatum and Geotrichum citri-aurantii, causes of green mold and sour rot of citrus, respectively, was quantified. In 3% wt/vol NaHCO₃ containing 200 µg free chlorine per ml at pH 8.3, 95% of P. digitatum spores died (LT₉₅) by 180 s at 5°C, while only 32 s were required at 24°C. The LT₉₅ of G. citri-aurantii arthrospores was 108 and 31 s at 5 and 24°C, respectively. Mortality slowed 2- to 4-fold for each unit of increase from pH 7 to 10. The LT₉₅ of P. digitatum spores in 200 µg free chlorine per ml at 24°C at pH 7, 8, 9, and 10 was 13.2, 19.1, 29.4, and 88.4 s, respectively. The LT₉₅ of G. citri-aurantii at pH 7, 8, 9, and 10 was 3.0, 12.6, 56.6, and 114 s, respectively. Models were prepared describing mortality. Brief immersion in 200 µg free chlorine per ml reduced viable spores of P. digitatum and G. citri-aurantii from 10⁶ to 10³ spores per lemon, and naturally occurring yeast and molds from 10⁶ to 10⁴ CFU. In fruit wound-inoculated and immersed 24 h later in water, 4,000 µg free chlorine per ml, or 3% wt/vol NaHCO₃, green mold occurrence after storage was 98.5, 68.3 and 7.5%, respectively.