First Report of Pilidium concavum Causing Tan-Brown Rot on Strawberry Fruit in Belgium

Soil mycobiome in sustainable agriculture

The soil microbiome contributes to several ecosystem processes. It plays a key role in sustainable agriculture, horticulture and forestry. In contrast to the vast number of studies focusing on soil bacteria, the amount of research concerning soil fungal communities is limited. This is despite the fact that fungi play a crucial role in the cycling of matter and energy on Earth. Fungi constitute a significant part of the pathobiome of plants. Moreover, many of them are indispensable to plant health. This group includes mycorrhizal fungi, superparasites of pathogens, and generalists; they stabilize the soil mycobiome and play a key role in biogeochemical cycles. Several fungal species also contribute to soil bioremediation through their uptake of high amounts of contaminants from the environment. Moreover, fungal mycelia stretch below the ground like blood vessels in the human body, transferring water and nutrients to and from various plants. Recent advances in high-throughput sequencing combined with bioinformatic tools have facilitated detailed studies of the soil mycobiome. This review discusses the beneficial effects of soil mycobiomes and their interactions with other microbes and hosts in both healthy and unhealthy ecosystems. It may be argued that studying the soil mycobiome in such a fashion is an essential step in promoting sustainable and regenerative agriculture.

Fungi Detected in the Previous Year’s Leaf Petioles of Fraxinus excelsior and Their Antagonistic Potential against Hymenoscyphus fraxineus

Studies on fungal communities in the previous year’s leaf petioles of Fraxinus excelsior found in litter in five ash stands in southern Poland were made in 2017. Fungi were identified on the basis of isolation from 300 surface sterilized leaf petioles and by in situ inventory of fruit bodies (on 600 petioles, in spring and autumn). Identification was based on morphology of colonies and fruit bodies, and sequencing of ITS region of the rRNA gene cluster. In total, 2832 isolates from 117 taxa (Ascomycota—100; Basidiomycota—15; Mucoromycota—2 taxa) were obtained with the isolation method. The most frequent taxa (with frequency >10%) were: Nemania serpens, Hymenoscyphus fraxineus, Alternaria sp. 1, Boeremia sp., Helotiales sp. 1, Epicoccum nigrum, Venturia fraxini, Fusarium sp., Fusarium lateritium, Nemania diffusa, Typhula sp. 2 (in descending order). In total, 45 taxa were detected with the in situ inventory method. Eleven taxa were classified as dominant: Hymenoscyphus fraxineus, Venturia fraxini, Leptosphaeria sp. 2, Cyathicula fraxinophila, Typhula sp. 2, Hypoderma rubi, Pyrenopeziza petiolaris, Cyathicula coronata, Hymenoscyphus scutula, Leptosphaeria sclerotioides and Hymenoscyphus caudatus. Among 202 leaf petioles colonized by H. fraxineus, 177 petioles also showed fructification of 26 other fungi. All the isolated saprotrophs were tested in dual-culture assay for antagonism to two strains of H. fraxineus. Three interaction types were observed: type A, mutual direct contact, when the two fungi meet along the contact line (occurred with 43.3% of test fungi); type B, with inhibition zone between colonies (with 46.9% of test fungi); type C, when the test fungus overgrows the colony of H. fraxineus (with 9.8% of test fungi). The possible contribution of the fungal saprotrophs in limiting of the expansion of H. fraxineus in ash leaf petioles, which may result in reduction in the inoculum of ash dieback causal agent, is discussed.

Trichoderma-Inoculated Miscanthus Straw Can Replace Peat in Strawberry Cultivation, with Beneficial Effects on Disease Control

Peat based growing media are not ecologically sustainable and often fail to support biological control. Miscanthus straw was (1) tested to partially replace peat; and (2) pre-colonized with a Trichoderma strain to increase the biological control capacity of the growing media. In two strawberry pot trials (denoted as experiment I & II), extruded and non-extruded miscanthus straw, with or without pre-colonization with T. harzianum T22, was used to partially (20% v/v) replace peat. We tested the performance of each mixture by monitoring strawberry plant development, nutrient content in the leaves and growing media, sensitivity of the fruit to the fungal pathogen Botrytis cinerea, rhizosphere community and strawberry defense responses. N immobilization by miscanthus straw reduced strawberry growth and yield in experiment II but not in I. The pre-colonization of the straw with Trichoderma increased the post-harvest disease suppressiveness against B. cinerea and changed the rhizosphere fungal microbiome in both experiments. In addition, defense-related genes were induced in experiment II. The use of miscanthus straw in growing media will reduce the demand for peat and close resource loops. Successful pre-colonization of this straw with biological control fungi will optimize crop cultivation, requiring fewer pesticide applications, which will benefit the environment and human health.