isolation-behavioral-identification-pathogenicity-assessment

Isolation, Behavioral Identification, and Pathogenicity Assessment of Entomopathogenic Fungi from a Forest Wood Borer

Forest wood borers (FWB) cause severe tree damage and economic losses worldwide. The release of entomopathogenic fungi (EPF) during the FWB emergence ...

Zhejiang A&F University

Recent disease outbreaks caused by alien invasive pathogens into European forests posed a serious threat to forest sustainability with relevant environmental and economic effects. Many of the alien tree pathogens recently introduced into Europe were not previously included on any quarantine lists, thus they were not subject to phytosanitary inspections. The identification and description of alien fungi potentially pathogenic to native European flora before their introduction in Europe, is a paramount need in order to limit the risk of invasion and the impact to forest ecosystems. To determine the potential invasive fungi, a sentinel trees plot was established in Fuyang, China, using healthy seedlings of European tree species including Quercus petreae, Q. suber, and Q. ilex. The fungal assemblage associated with symptomatic specimens was studied using the tag-encoded 454 pyrosequencing of the nuclear ribosomal internal transcribed spacer-1 (ITS 1). Taxa with probable Asiatic origin were identified and included plant pathogenic genera. These results indicate that sentinel plants may be a strategic tool to improve the prevention of bioinvasions.

Sentinel trees as a tool to forecast invasions of alien plant pathogens.

International trade in plants and climate change are two of the main factors causing damaging tree pests (i.e. fungi and insects) to spread into new areas. To mitigate these risks, a large-scale assessment of tree-associated fungi and insects is needed. We present records of endophytic fungi and insects in twigs of 17 angiosperm and gymnosperm genera, from 51 locations in 32 countries worldwide. Endophytic fungi were characterized by high-throughput sequencing of 352 samples from 145 tree species in 28 countries. Insects were reared from 227 samples of 109 tree species in 18 countries and sorted into taxonomic orders and feeding guilds. Herbivorous insects were grouped into morphospecies and were identified using molecular and morphological approaches. This dataset reveals the diversity of tree-associated taxa, as it contains 12,721 fungal Amplicon Sequence Variants and 208 herbivorous insect morphospecies, sampled across broad geographic and climatic gradients and for many tree species. This dataset will facilitate applied and fundamental studies on the distribution of fungal endophytes and insects in trees.

Worldwide diversity of endophytic fungi and insects associated with dormant tree twigs.

Forced air heat treatment could induce defenses to protect fruit from pathogen attacks and has been applied as an alternative to methyl bromide for phytosanitary treatment before exportation. However, few studies were reported on the regulation mechanism of antifungal effect and delayed physiological disorders of papaya by heat treatment. Therefore, we aim to explore the fruit's resistance to pathogens and the inhibition of physiological disorders by metabolomic profiling. In our study, papaya fruits were treated with 47.2°C for 30, 60, and 90 min by forced hot air treatment. The disease resistance against , quality parameters, and metabolites of papaya fruits were measured during 10 days of storage after heat treatment by metabolomic profiling. Papaya fruits after 30 and 60 min heat treatment had higher firmness, a delayed degreening and yellowing (lower a value) process, and a higher lightness (L) and hue angle (h) during storage. Heat treatment also delayed ripening, inhibiting the growth of  and softening of papaya. Metabolites and enzymes inhibited ROS scavenging, depressed ABA-regulated respiratory, and activated phenylpropanoid metabolism. Our study provides a broad picture of fruit resistance to pathogens and the inhibition of physiological disorders by metabolomic profiling, which is induced by heat treatment.

Hot Air Treatment Elicits Disease Resistance against  and Improves the Quality of Papaya by Metabolomic Profiling.

In insects, the chemosensory system is crucial in guiding their behaviors for survival. Plagiodera versicolora (Coleoptera: Chrysomelidae), is a worldwide leaf-eating forest pest in salicaceous trees. There is little known about the chemosensory genes in P. versicolora. Here, we conducted a transcriptome analysis of larvae heads in P. versicolora.

Transcriptome analysis and identification of chemosensory genes in the larvae of Plagiodera versicolora.

Complex interspecific relationships between parasites and their insect hosts involve multiple factors and are affected by their ecological and evolutionary context. A parasitoid  (Hymenoptera: Bethylidae) and an entomopathogenic fungus  (Hypocreales: Cordycipitaceae) shared the same host in nature,  (Coleoptera: Cerambycidae). They often encountered the semi-enclosed microhabitat of the host larvae or pupae. We tested the survival and reproduction of the parasitoid's parent and its offspring fitness under different concentrations of  suspension. The results show that  parent females carrying higher concentrations of the pathogen shorten the pre-reproductive time and regulate their own fertility and their offspring's survival and development. This minimal model of the interspecific interactions contains three dimensionless parameters, vulnerability (), dilution ratio (), and , which were used to evaluate the mortality effect of the parasitoid  on its host  under the stress of the entomopathogenic fungus . We compared the infection and lethal effect of the fungus  with different concentrations to the parasitoid  and the host larvae . At higher concentrations of the pathogen, the parasitoid parent females shorten the pre-reproductive time and regulate their own fertility and their offspring's survival and development. At moderate concentrations of the pathogen, however, the ability of the parasitoid to exploit the host is more flexible and efficient, possibly reflecting the potential interspecific interactions between the two parasites which were able to coexist and communicate with their hosts in ecological contexts (with a high overlap in time and space) and cause interspecific competition and intraguild predation.

Adaptive Reproductive Strategies of an Ectoparasitoid  under the Stress of Its Entomopathogenic Fungus .

Correction: Transcriptome analysis and identification of chemosensory genes in the larvae of Plagiodera versicolora.

Non-native pests, climate change, and their interactions are likely to alter relationships between trees and tree-associated organisms with consequences for forest health. To understand and predict such changes, factors structuring tree-associated communities need to be determined. Here, we analysed the data consisting of records of insects and fungi collected from dormant twigs from 155 tree species at 51 botanical gardens or arboreta in 32 countries. Generalized dissimilarity models revealed similar relative importance of studied climatic, host-related and geographic factors on differences in tree-associated communities. Mean annual temperature, phylogenetic distance between hosts and geographic distance between locations were the major drivers of dissimilarities. The increasing importance of high temperatures on differences in studied communities indicate that climate change could affect tree-associated organisms directly and indirectly through host range shifts. Insect and fungal communities were more similar between closely related vs. distant hosts suggesting that host range shifts may facilitate the emergence of new pests. Moreover, dissimilarities among tree-associated communities increased with geographic distance indicating that human-mediated transport may serve as a pathway of the introductions of new pests. The results of this study highlight the need to limit the establishment of tree pests and increase the resilience of forest ecosystems to changes in climate.

Jianting Fan

School of Forestry and Biotechnology

Zhejiang A&F University

Isolation, Behavioral Identification, and Pathogenicity Assessment of Entomopathogenic Fungi from a Forest Wood Borer