Search

Fusarium circinatum Nirenberg & O'Donnel is listed among the species recommended for regulation as quarantine pests in Europe. Over 60 Pinus species are susceptible to the pathogen and it also causes disease on Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) and species in genera such as Picea and Larix. The European Food Safety Authority considers the probability of new introductions—via contaminated seeds, wood material, soil and growing substrates, natural means and human activities—into the EU very likely. Due to early detection, constant surveillance and control measures, F. circinatum outbreaks have officially been eradicated in Italy and France. However, the global spread of F. circinatum suggests that the pathogen will continue to be encountered in new environments in the future. Therefore, continuous surveillance of reproductive material, nurseries and plantations, prompt control measures and realistic contingency plans will be important in Europe and elsewhere to limit disease spread and the "bridgehead effect", where new introductions of a tree pathogen become increasingly likely as new environments are invaded, must be considered. Therefore, survey programs already implemented to limit the spread in Europe and that could be helpful for other EU countries are summarized in this review. These surveys include not only countries where pitch canker is present, such as Portugal and Spain, but also several other EU countries where F. circinatum is not present. Sampling protocols for seeds, seedlings, twigs, branches, shoots, soil samples, spore traps and insects from different studies are collated and compiled in this review. Likewise, methodology for morphological and molecular identification is herein presented. These include conventional PCR with a target-specific region located in the intergenic spacer region, as well as several real-time PCR protocols, with different levels of specificity and sensitivity. Finally, the global situation and future perspectives are addressed. [ABSTRACT FROM AUTHOR]

Fusarium circinatum is the causal agent of pine pitch canker disease (PPC), affecting Pinus species and other conifers (i.e., Pseudotsuga menziesii (Mirb.) Franco.), forming resinous cankers on the main stem and branches and causing dieback in the terminal guide. This pathogen is spreading worldwide, causing economic losses by converting plantations into standing timber without any potential for future production. The disease was recently detected in Northern Spain in plantations of Pinus radiata and forest nurseries. The aim of the work reported here was to study the role of climatic and topographic variables, soil properties, and stand characteristics on PPC. For this purpose, we surveyed 50 pine stands in Cantabria and quantified the percentage of trees showing three symptoms in each stand: canker, defoliation, and dieback. We investigated the predictive power of 30 variables using generalized linear models and hierarchical partitioning. Both approaches yielded similar results. We found that the three symptoms correlated with different explanatory variables. In addition, more trees exhibited cankers in the proximity of the coast and the Basque Country. Additionally, our results showed that low canopy cover is related to a high level of the dieback symptom. Overall, this study highlights the important variables affecting the distribution of PPC in Cantabria. [ABSTRACT FROM AUTHOR]

Fusarium spp., as well as other endophytic or pathogenic fungi that form communities, have been reported to be phoretically associated with bark beetles (Coleoptera; Scolytinae) worldwide. This applies to Fusarium circinatum Nirenberg and O'Donnell, the causal agent of pine pitch canker (PPC), which threatens Pinus radiata D. Don plantations in northern Spain. The main objective of this study was to study the fungal communities associated with bark beetles and their galleries in stands affected by PPC, with special attention given to Fusarium species. Funnel traps and logs were placed in a P. radiata plot known to be affected by F. circinatum. The traps were baited with different attractants: four with (E)-pityol and six with ethanol and α-Pinene. In addition, fresh green shoots with Tomicus piniperda L. feeding galleries were collected from the ground in 25 P. radiata plots affected by PPC. Extracts of whole insects and gallery tissues were plated on agar medium to isolate and identify the associated fungi. A total of 24 different fungal species were isolated from the bark beetle galleries constructed in logs and shoots, while 18 were isolated from the insect exoskeletons. Ten different Fusarium species were isolated from tissue and insects. Fusarium circinatum was isolated from bark beetle exoskeletons (1.05% of the Pityophthorus pubescens Marsham specimens harboured F. circinatum) and from the galleries (3.5% of the T. piniperda feeding galleries harboured the pathogen). The findings provide information about the fungal communities associated with bark beetles in P. radiata stands in northern Spain. [ABSTRACT FROM AUTHOR]

Pine Pitch Canker disease, caused by the pathogenic fungus Fusarium circinatum, affects conifer species worldwide. However, the virulence of the pathogen may be affected by the presence of mycoviruses. The aim of this laboratory-based study was to investigate the probability and rate of transmission of F. circinatum mitoviruses FcMV1 and FcMV2-2 via microconidia. Ten isolates of mitovirus-infected F. circinatum were subcultured to produce a total of 100 single-spore colonies (ten replicates per isolate). The total RNA and cDNA obtained from each spore isolate (monosporic culture) were amplified by PCR with specific primers for detection of F. circinatum mitoviruses FcMV1 and FcMV2-2. The mitoviruses were detected in a high percentage of the individual spore isolates (between 60% and 100% depending on the fungal isolate). However, the probability of transmission was not statistically significantly associated with either the F. circinatum isolate or the viral strain. A high proportion of transmission via microconidia is critical for development of a biological control program against Pine Pitch Canker (PPC) disease in forests. However, further studies are needed to establish the effect of these mitoviruses on the virulence of F. circinatum. [ABSTRACT FROM AUTHOR]