Biocontrol of Diseases Caused by Phytophthora capsici and P. parasitica in Pepper Plants.

The main objective of this study was to evaluate the ability of Trichoderma aggressivum f. europaeum, T. longibrachiatum, Paecilomyces variotii, and T. saturnisporum as biological control agents (BCAs) against diseases caused by P. capsici and P. parasitica in pepper. For this purpose, their antagonistic activities were evaluated both in vitro and in vivo. We analysed the expression patterns of five defence related genes, CaBGLU, CaRGA1, CaBPR1, CaPTI1, and CaSAR8.2, in leaves. All BCAs showed a high in vitro antagonistic activity, significantly reducing the mycelial growth of P. capsici and P. parasitica. The treatments with T. aggressivum f. europaeum, T. longibrachiatum, and P. variotii substantially reduced the severity of the disease caused by P. capsici by 54, 76, and 70%, respectively, and of the disease caused by P. parasitica by 66, 55, and 64%, respectively. T. saturnisporum had the lowest values of disease reduction. Reinoculation with the four BCAs increased the control of both plant pathogens. Markedly different expression patterns were observed in the genes CaBGLU, CaRGA1, and CaSAR8.2. Based on the results, all four BCAs under study could be used as a biological alternative to chemicals for the control of P. capsici and P. parasitica in pepper with a high success rate.

Biological Control of Fungal Diseases by Trichoderma aggressivum f. europaeum and Its Compatibility with Fungicides.

Our purpose was to evaluate the ability of Trichoderma aggressivum f. europaeum as a biological control agent against diseases from fungal phytopathogens. Twelve isolates of T. aggressivum f. europaeum were obtained from several substrates used for Agaricus bisporus cultivation from farms in Castilla-La Mancha (Spain). Growth rates of the 12 isolates were determined, and their antagonistic activity was analysed in vitro against Botrytis cinerea, Sclerotinia sclerotiorum, Fusarium solani f. cucurbitae, Pythium aphanidermatum, Rhizoctonia solani, and Mycosphaerella melonis, and all isolates had high growth rates. T. aggressivum f. europaeum showed high antagonistic activity for different phytopathogens, greater than 80%, except for P. aphanidermatum at approximately 65%. The most effective isolate, T. aggressivum f. europaeum TAET1, inhibited B. cinerea, S. sclerotiorum, and M. melonis growth by 100% in detached leaves assay and inhibited germination of S. sclerotiorum sclerotia. Disease incidence and severity in plant assays for pathosystems ranged from 22% for F. solani to 80% for M. melonis. This isolate reduced the incidence of Podosphaera xanthii in zucchini leaves by 66.78%. The high compatibility by this isolate with fungicides could allow its use in combination with different pest management strategies. Based on the results, T. aggressivum f. europaeum TAET1 should be considered for studies in commercial greenhouses as a biological control agent.

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.

Cultivation of Agaricus bitorquis mushroom as an strategy for the Integrated Pest Management of the myceliophagous mite Microdispus lambi.

BACKGROUND: The phorid fly Megaselia halterata Winnertz (Diptera: Phoridae) is the principal vector of Microdispus lambi (Acari: Pygmephoroidea) in Spanish Agaricus bisporus Lange (Imbach) mushroom farms. This myceliophagous mite does not appear to be a pest in Agaricus bitorquis (Quél.) Sacc mushroom crops. This study explores the role of phorid flies as vectors of Microdispus lambi in Agaricus bitorquis mushroom crops. RESULTS: The incidence of M. lambi in A. bitorquis growing substrates did not reach appreciable levels at any point during the growing cycle. The presence of phorid flies in A. bitorquis farms was normally higher than that in the case of Agaricus bisporus Lange (Imbach) species. The percentage of phorid vectors did not statistically differ between both Agaricus crops during infection periods. However, by the end of the crop, this percentage had increased only in A. bisporus crops, coinciding with a high incidence of mites in the substrate of this mushroom species; Megaselia halterata emerging from the mushroom substrate of A. bitorquis summer crops did not carry mites as they were absent from compost and casing. CONCLUSION: M. halterata is a pest in Spanish A. bitorquis mushroom crops, meanwhile M. lambi, its phorectic mite, has shown not to be a pest of this species mushroom farms during the spring-summer growing season. A. bitorquis crops could potentially be used as an IPM measure to decrease the incidence and prevent the propagation of the myceliophagous mite M. lambi in A. bisporus mushroom growing farms. © 2020 Society of Chemical Industry.

Plant Growth Promotion and Biocontrol of Pythium ultimum by Saline Tolerant Trichoderma Isolates under Salinity Stress.

This present study evaluates three isolates of Trichoderma as plant growth promoting or biological control agents: Trichoderma aggressivum f. sp. europaeum, Trichoderma saturnisporum, and the marine isolate obtained from Posidonia oceanica, Trichoderma longibrachiatum. The purpose is to contribute to an overall reduction in pesticide residues in the fruit and the environment and to a decrease in chemical fertilizers, the excess of which aggravates one of the most serious abiotic stresses, salinity. The tolerance of the different isolates to increasing concentrations of sodium chloride was evaluated in vitro, as well as their antagonistic capacity against Pythium ultimum. The plant growth promoting capacity and effects of Trichoderma strains on the severity of P. ultimum on melon seedlings under saline conditions were also analysed. The results reveal that the three isolates of Trichoderma, regardless of their origin, alleviate the stress produced by salinity, resulting in larger plants with an air-dry weight percentage above 80% in saline stress conditions for T. longibrachiatum, or an increase in root-dry weight close to 50% when T. aggressivum f. sp. europaeum was applied. Likewise, the three isolates showed antagonistic activity against P. ultimum, reducing the incidence of the disease, with the highest response found for T. longibrachiatum. Biological control of P. ultimum by T. aggressivum f. sp. europaeum and T. saturnisporum is reported for the first time, reducing disease severity by 62.96% and 51.85%, respectively. This is the first description of T. aggressivum f. sp. europaeum as a biological control agent and growth promoter. The application of these isolates can be of enormous benefit to horticultural crops, in both seedbeds and greenhouses.

Evaluation of residue risk and toxicity of different treatments with diazinon insecticide applied to mushroom crops.

This work describes the phytotoxic effect of different doses of diazinon and different application times on Agaricus bisporus mycelium, and determines the residue levels in mushrooms from the first three flushes. Mushroom cultivation is a widespread commercial activity throughout the world. The application of insecticide diazinon to the compost or casing layer is a common practice to control two mushroom pests, the phorid Megaselia halterata and the sciarid Lycoriella auripila. Application to the compost does not result in any appreciable fall in yield or quality, and does not delay the harvest time. In contrast, application to the casing led to a slight fall (6.2%) in production and a smaller number of mushrooms although they are larger in size. Residue levels of more than 0.01 ppm are detected in many of the samples analyzed, and raising the question whether the product should continue to be used in mushroom cultivation in the conditions in which it is currently applied.

Characters of compost teas from different sources and their suppressive effect on fungal phytopathogens.

Compost teas (CT) are fermented watery extracts of composted materials that are used to control plant diseases and on crop fertilization. In this work, aerated (ACT) and non-aerated compost teas (NCT) were obtained from four different composts: spent mushroom substrate compost, grape marc compost, greenhouse horticultural crop residues compost, and vermicompost. Physico-chemical and microbiological analysis were carried out to determine their properties. In vitro assays were performed to assess their suppressive effect on the mycelial growth of eight fungal phytopathogens. In vivo trials aimed to assess their effect on gummy stem blight (Didymella bryonae) and powdery mildew (Podosphaera fusca) in melon plants. Results showed that ACT and NCT filtrates inhibited the in vitro growth of all tested pathogens while autoclaved CT did not completely lose their inhibitory effect, and CT sterilized by microfiltration had no effect on the pathogen growth. The severity of powdery mildew was highly reduced by ACT and NCT from all sources, though in gummy stem blight assay only a delay in disease development was observed. In general, all compost teas showed a high level of microbial populations and nutrients. Results suggest that the efficacy of ACT and NCT firstly depend on the microbiota present in them. We consider compost teas from the four tested sources as a viable way to manage plant diseases and crop fertilization, throughout its integration in pest management programs and fertirrigation systems under different dilution rates.

Effect of spent mushroom compost tea on mycelial growth and yield of button mushroom (Agaricus bisporus).

Preliminary studies suggested that the use of compost tea made from spent mushroom substrate (SMS) may be regarded as a potential method for biologically controlling dry bubble disease in button mushroom. The aim of this study was to assess the effect of SMS compost tea on the host, the button mushroom, to ascertain whether the addition of these water extracts has a toxic effect on Agaricus bisporus mycelium growth and on mushroom yield. In vitro experiments showed that the addition of SMS compost tea to the culture medium inoculated with a mushroom spawn grain did not have an inhibitory effect on A. bisporus mycelial growth. The effect of compost teas on the quantitative production parameters of A. bisporus (yield, unitary weight, biological efficiency and earliness) was tested in a cropping trial, applying the compost teas to the casing in three different drench applications. Quantitative production parameters were not significantly affected by the compost tea treatments although there was a slight delay of 0.8-1.4 days in the harvest time of the first flush. These results suggest that compost teas have no fungitoxic effect on A. bisporus so that they can be considered a suitable biocontrol substance for the control of dry bubble disease.

Reduced sensitivity of the mushroom pathogen Verticillium fungicola to prochloraz-manganese in vitro.

105 isolates of Verticillium fungicola from Spanish mushroom crops collected between 1992 and 1999 were tested in vitro for their sensitivities to prochloraz-manganese. Dose response relationships for inhibition of mycelial growth by the fungicide were assessed in radial growth experiments on fungicide-amended malt extract agar. The ED50 values recorded for all 105 isolates studied ranged between 0.8 ppm in 1992 and 8.8 in 1998, with an average of 2.9. 86% of the isolates tested were more sensitive to prochloraz-manganese and had ED50 values below 5 ppm, while the other 14% were slightly tolerant with ED50 values equal or above 5 ppm. Of those tested from 1999, 60% (21 isolates) grew with 50 ppm and 40% (14) also at 100 ppm, although mycelial growth was inhibited at least by 82 and 87%, respectively. The resistance factor calculated ranged from low fungicide resistance (RF=3.0) in 1992 to moderate resistance (RF=12.6) in 1998. These data confirm that the sensitivity of V. fungicola to the prochloraz-manganese gradually diminishes.