Endophytic Fungi and Ecological Fitness of Chestnuts

Cladosporium-Insect Relationships

The range of interactions between Cladosporium, a ubiquitous fungal genus, and insects, a class including about 60% of the animal species, is extremely diverse. The broad case history of antagonism and mutualism connecting Cladosporium and insects is reviewed in this paper based on the examination of the available literature. Certain strains establish direct interactions with pests or beneficial insects or indirectly influence them through their endophytic development in plants. Entomopathogenicity is often connected to the production of toxic secondary metabolites, although there is a case where these compounds have been reported to favor pollinator attraction, suggesting an important role in angiosperm reproduction. Other relationships include mycophagy, which, on the other hand, may reflect an ecological advantage for these extremely adaptable fungi using insects as carriers for spreading in the environment. Several Cladosporium species colonize insect structures, such as galleries of ambrosia beetles, leaf rolls of attelabid weevils and galls formed by cecidomyid midges, playing a still uncertain symbiotic role. Finally, the occurrence of Cladosporium in the gut of several insect species has intriguing implications for pest management, also considering that some strains have proven to be able to degrade insecticides. These interactions especially deserve further investigation to understand the impact of these fungi on pest control measures and strategies to preserve beneficial insects.

Pilot Study on the Geographical Mapping of Genetic Diversity among European Chestnut (Castanea sativa Mill.) Cultivars in Southern Italy

Knowledge of the spatial distribution of European chestnut (Castanea sativa Mill.) cultivar diversity is essential for managing and conserving the genetic resources of this fruit tree species in Southern Italy. To this goal, the present work investigated the feasibility of mapping, through spatial representation, the distribution of genetic diversity of traditional chestnut varieties in the area of the Roccamonfina Regional Park in the Campania Region. After Principal Coordinates Analysis (PCoA) of molecular-genetic data, chestnuts formed varietal groups in a leopard spot on PCoA plots with a relatively high degree of genetic diversity. Successively, a Geographic Information System (GIS) tool utilized these molecular-genetic data to create a genetic divergence surface by geospatial interpolation on the geographic map of the Regional Park corresponding to each chestnut variety. The regions containing more biodiversity richness resulted in differentially colored from those containing cultivars less genetically distant from each other; thus, the area in study was consistently colored according to the allelic richness as evaluated by molecular-genetic markers. The combined use of tools for molecular and spatial analysis allowed for drafting genetic landscapes with the aim of extracting useful information for the safeguarding of the chestnut biodiversity at risk.

A Review of the Stress Resistance, Molecular Breeding, Health Benefits, Potential Food Products, and Ecological Value of Castanea mollissima

Chestnut (Castanea spp., Fagaceae family) is an economically and ecologically valuable species. The main goals of chestnut production vary among species and countries and depend on the ecological characteristics of orchards, agronomic management, and the architecture of chestnut trees. Here, we review recent research on chestnut trees, including the effects of fungal diseases (Cryphonectria parasitica and Phytophthora cinnamomi) and insect pests (Dryocosmus kuriphilus Yasumatsu), molecular markers for breeding, ecological effects, endophytic fungi, and extracts with human health benefits. We also review research on chestnut in the food science field, technological improvements, the soil and fertilizer used for chestnut production, and the postharvest biology of chestnut. We noted differences in the factors affecting chestnut production among regions, including China, the Americas, and Europe, especially in the causal agents of disease and pests. For example, there is a major difference in the resistance of chestnut to C. parasitica in Asian, European, and American countries. Our review provides new insights into the integrated disease and pest management of chestnut trees in China. We hope that this review will foster collaboration among regions and help to clarify differences in the direction of breeding efforts among countries.

Biocontrol of Phytophthora xcambivora on Castanea sativa: Selection of Local Trichoderma spp. Isolates for the Management of Ink Disease

Ink disease is a devastating disease of chestnut (Castanea sativa) worldwide, caused by Phytophthora species. The only management measures of this disease are chemical and agronomic interventions. This work focuses on the evaluation of the in vitro antagonistic capacity of 20 isolates of Trichoderma spp. selected in a diseased chestnut orchard in Tuscan Apennines (San Godenzo, Italy) for the biocontrol of Phytophthora xcambivora. Each Trichoderma isolate was tested to investigate pathogen inhibition capability by antagonism in dual cultures and antibiosis by secondary metabolites production (diffusible and Volatile Organic Compounds). The six most performing isolates of Trichoderma spp. were further assessed for their aptitude to synthesize chitinase, glucanase and cellulase, and to act as mycoparasite. All six selected isolates displayed the capability to control the pathogen in vitro by synergistically coupling antibiosis and mycoparasitism at different levels regardless of the species they belong to, but rather, in relation to specific features of the single genotypes. In particular, T. hamatum SG18 and T. koningiopsis SG6 displayed the most promising results in pathogen inhibition, thus further investigations are needed to confirm their in vivo efficacy.