The Epidemic Spread of Seiridium cardinale on Leyland Cypress Severely Limits Its Use in the Mediterranean

Leyland cypress (× Hesperotropsis leylandii) is a fast-growing conifer used in most temperate regions as an ornamental tree for hedges and screens, and is one of the most commercially important trees in Europe. In recent years, severe diebacks and mortality due to cypress canker have been observed on Leyland cypress plantations in Southern Europe. This study was conducted to evaluate (i) the spread and impact of cypress canker caused by Seiridium cardinale in plantations of a sample area of 1,250 km2 in central Italy, (ii) the response of the most commonly grown Leyland cypress varieties to artificial inoculation with to S. cardinal, and (iii) the pathogenicity of S. cardinale isolates obtained from Leyland cypress. Of the 1,411 surveyed trees, 11.4% had been killed by cypress canker and 43.9% of the living trees were affected by the disease. The number of diseased or dead trees and the percentage of cankered trunks was significantly correlated with the mean trunk diameter of the plantations. Six months after inoculation, the size of developed cankers was significantly different among the inoculated Leyland cypress cultivars but all of them showed markedly larger cankers than the C. sempervirens canker-resistant control clone. All of the tested S. cardinale isolates obtained from Leyland cypress also caused cankers on Cupressus sempervirens when inoculated as conidial suspensions or mycelia. Leyland cypress is highly prone to contract cypress canker in the Mediterranean due to its high susceptibility to S. cardinale infections, low genetic variability among the grown cultivars, and cracks which form on fast-growing trunks, favoring entry of the fungus into the inner bark and the occurrence of infections

Newly-assessed fungicides for the control of cypress canker caused by Seiridium cardinale

Bark canker caused by Seiridium cardinale is the most destructive disease of Cupressus and several Cupressaceae in many temperate regions and particularly in the Mediterranean area. Chemical prevention represents the most effective and essential means of control to protect plant production in nurseries and young plantations. The European Directive 2009/128/CE and CE 1107/2009 application have drastically reduced the number of chemicals that can be used in agriculture, including the benzimidazolic compounds that had shown the best results in preventing S. cardinale canker. It is therefore urgent to find alternative fungicides to replace the banned compounds. The purpose of the present work was to assess some fungicides through in vitro tests and pre- and post-inoculation sprayings on Cupressus sempervirens, for the control of S. cardinale. The active ingredients boscalid, fosetyl-aluminium, triadimenol and azoxystrobin were compared with thiophanate-methyl as reference. The effectiveness of thiophanate-methyl in reducing canker development was confirmed especially when it was applied to trees before they were inoculated with S. cardinale. Azoxystrobin was as effective as thiophanate-methyl in the pre-inoculation trials. boscalid prevented conidial germination and mycelial growth of S. cardinale in vitro and appeared a promising contact fungicide for the prevention of cypress canker. Azoxystrobin and boscalid are listed in a less hazardous class than thiophanate-methyl, and has less risk for the environment and for users

Strategies for Fast Multiplication and Conservation of Forest Trees by Somatic Embryogenesis and Cryopreservation: a Case Study with Cypress (Cupressus sempervirens L.)

Common cypress (Cupressus sempervirens L.) is one of the most widespread species in the Mediterranean area. It has been traditionally cultivated for its ornamental value, becoming a typical feature of urban and rural landscapes, and high timber quality. In the last 30 years, cypress has been subjected to important breeding programmes, aimed to select clones tolerant to the widespread canker, caused by the pathogenic fungus Seiridium cardinale, leading to various patented varieties today available on the market, as well as for genotypes producing null or low amount of allergenic pollen. Somatic embryogenesis is a suitable in vitro regeneration method for fast cloning of conifer trees, and the cryopreservation of embryogenic callus is a significant tool for the safe long-term conservation of valuable cell lines. Recently, a complete protocol for the production of cypress plants from somatic embryogenesis was developed for the patented clone 'Mediterraneo'. Here, the coupling of somatic embryogenesis and cryopreservation may offer a superior tool to propagate and maintain selected genotypes of cypress by overcoming repetitive subculturing of selected embryogenic callus lines. For the above, this study aimed to compare different cryopreservation techniques (PVS2-based vitrification and slow cooling) with the 'Mediterraneo' embryogenic callus line. Best results were obtained after the optimization of a slow cooling procedure, based on the 30-min treatment of embryogenic masses with a cryoprotective solution containing 180 g l-1 sucrose and 7.5% DMSO, followed by the reduction of the temperature at a rate of -1 °C min-1 up to -40 °C and the subsequent immersion in liquid nitrogen ("two-step freezing")

A new additional record of Phloeosinus armatus Reitter from Italy (Coleoptera Curculionidae Scolytinae)

In the early 1990s, outbreaks of the Cypress bark beetle Phloeosinus armatus Reitter were reported on Cupressus sempervirens L. and C. arizonica Sarg. in north-western Italy (Liguria). About 10 years later, this bark beetle, whose distribution range is originally the eastern Mediterranean, was found again in the same region on rows and isolated plants of Mediterranean cypress. In this paper P. armatus is reported for the first time on C. sempervirens in central Italy (Tuscany), where this insect species is widespread both on ornamental trees and on woodland formations. A taxonomic key is presented for the identification of both the male and female adults of P. armatus among species of the genus Phloeosinus Chapuis living on Cupressaceae in south-western Europe. Due to its greater size, compared with the indigenous species P. aubei, and the behavioural similarities in the adult maturation phase among the two species, P. armatus could convey large quantities of inoculum of the fungus Seiridium cardinale (Wagener) Sutton et Gibson, causal agent of cypress canker. The need for extensive monitoring and specific research for the development of attractants and traps to capture the adult bark beetles is emphasized

Terpene arms race in the Seiridium cardinale - Cupressus sempervirens pathosystem

The canker-causing fungus Seiridium cardinale is the major threat to Cupressus sempervirens worldwide. We investigated the production of terpenes by canker-resistant and susceptible cypresses inoculated with S. cardinale, the effect of these terpenes on fungal growth, and the defensive biotransformation of the terpenes conducted by the fungus. All infected trees produced de novo terpenes and strongly induced terpenic responses, but the responses were stronger in the cankerresistant than the susceptible trees. In vitro tests for the inhibition of fungal growth indicated that the terpene concentrations of resistant trees were more inhibitory than those of susceptible trees. The highly induced and de novo terpenes exhibited substantial inhibition (more than a fungicide reference) and had a high concentration-dependent inhibition, whereas the most abundant terpenes had a low concentration-dependent inhibition. S. cardinale biotransformed three terpenes and was capable of detoxifying them even outside the fungal mycelium, in its immediate surrounding environment. Our results thus indicated that terpenes were key defences efficiently used by C. sempervirens, but also that S. cardinale is ready for the battle

Strong induction of minor terpenes in Italian cypress, Cupressus sempervirens, in response to infection by the fungus Seiridium cardinale

Altres ajuts: Project CypFire EC/2G-MED09-070Seiridium cardinale, the main fungal pathogen responsible for cypress bark canker, is the largest threat to cypresses worldwide. The terpene response of canker-resistant clones of Italian cypress, Cupressus sempervirens, to two differently aggressive isolates of S. cardinale was studied. Phloem terpene concentrations, foliar terpene concentrations, as well as foliar terpene emission rates were analyzed 1, 10, 30, and 90 days after artificial inoculation with fungal isolates. The phloem surrounding the inoculation point exhibited de novo production of four oxygenated monoterpenes and two unidentified terpenes. The concentrations of several constitutive mono- and diterpenes increased strongly (especially α- thujene, sabinene, terpinolene, terpinen-4-ol, oxygenated monoterpenes, manool, and two unidentified diterpenes) as the infection progressed. The proportion of minor terpenes in the infected cypresses increased markedly from the first day after inoculation (from 10 % in the control to 30-50 % in the infected treatments). Foliar concentrations showed no clear trend, but emission rates peaked at day 10 in infected trees, with higher δ-3-carene (15-fold) and total monoterpene (10-fold) emissions than the control. No substantial differences were found among cypresses infected by the two fungal isolates. These results suggest that cypresses activate several direct and indirect chemical defense mechanisms after infection by S. cardinale

Responses of a soil fungal community to severe windstorm damages in an old silver fir stand

Forests are increasingly threatened by climate change and the Anthropocene seems to have favored the emergence and adaptation of pathogens. Robust monitoring methods are required to prevent biodiversity and ecosystems losses, and this imposes the choice of bioindicators of habitat health. Fungal communities are increasingly recognized as fundamental components in nearly all natural and artificial environments, and their ecosystem services have a huge impact in maintaining and restoring the functionality of ecosystems. We coupled metabarcoding and soil analyses to infer the dynamics of a fungal community inhabiting the old silver fir stand in Vallombrosa (Italy), which is known to be afflicted by both Armillaria and Annosum root rot. The forest was affected in 2015, by a windstorm which caused a partial falling and uprooting of trees. The remaining stand, not affected by the windstorm, was used as a comparison to infer the consequences of the ecosystem disturbance. We demonstrated that the abundance of pathogens alone is not able to explain the soil fungal differences shown by the two areas. The fungal community as a whole was equally rich in the two areas, even if a reduction of the core ectomycorrhizal mycobiome was observed in the wind-damaged area, accompanied by the increase of wood saprotrophs and arbuscular mycorrhizas. We hypothesize a reshaping of the fungal community and a potentially ongoing re-generation of its functionalities. Our hypothesis is driven by the evidence that key symbiotic, endophytic, and saprotrophic guilds are still present and diversified in the wind-damaged area, and that dominance of single taxa or biodiversity loss was not observed from a mycological point of view. With the present study, we aim at providing evidence that fungal communities are fundamental for the monitoring and the conservation of threatened forest ecosystems

Innovative In Situ and Ex Situ Conservation Strategies of the Madonie Fir Abies nebrodensis

Abies nebrodensis (Lojac.) Mattei is an endemic species of the north-west of Sicily located in an 84 ha area in the Madonie Regional park. The current population is limited to 30 relic adult trees and a fluctuating number of juveniles of natural regeneration. The species is defined as “Critically Endangered” in the Italian list of threatened plants and is classified as CR-D in the 2000 IUCN Red List of Threatened Species. This article reports the key action undertaken by the LIFE4FIR project aimed at preserving A. nebrodensis, and the results obtained so far in three years of activity. OpenArrays SNPs genotyping revealed a high rate of inbreeding in the natural population and that the adult trees are genetically related. Controlled cross-pollination was consequently performed to increase the genetic variability of the progeny. Outbred offspring are currently being grown in the nursery. Reforestation has been planned by using 4000 selected outbred seedlings in 10 areas within Madonie Park to create re-diffusion cores. Support and protection of the relic population have been implemented through regular phytosanitary surveys, as well as new fencing and video surveillance systems against grazing and wild herbivores. A seedbank and cryobank for the long-term germplasm conservation have been established.European Union LIFE18/NAT/IT/00016

Flammability of Two Mediterranean Mixed Forests: Study of the Non-additive Effect of Fuel Mixtures in Laboratory

In the Mediterranean region, wildfires are a major disturbance, determined by ecosystem and forest species characteristics. Both the flammability and resistance to fire of a mixed forest may vary from those of the individual species. Two mixed Mediterranean woodlands, a Cupressus sempervirens and Quercus ilex stand in Italy; and a Juniperus thurifera and Quercus faginea stand in Spain were investigated. Laboratory flammability tests were conducted on live foliage, litter samples and on litter beds from individual and mixed species to evaluate: (i) the flammability traits of the mixtures of live foliage and litter samples; (ii) whether the flammability of the two-species mixtures are non-additive, i.e., differ from expected flammability based on arithmetic sum of the single effects of each components species in monospecific fuel; (iii) the ignition success and initial fire propagation in litter beds. Flammability tests were also conducted on bark samples to estimate the resistance of the tree species to fire. The ignitibility of live foliage was lower and the combustibility was higher in Cupressaceae than in Quercus. Non-additive effects were observed in some flammability components of live foliage and litter, especially in the mixtures of C. sempervirens and Q. ilex. Ignitability and combustibility were higher and lower than expected, respectively, and tended to be driven by Quercus), while the consumability was lowered more than expected by both Cupressaceae. The ignition success in the litter beds was low, especially for the presence of Cupressaceae that increase the bulk density of the mixtures. Cupressaceae, which have a thinner bark, suffered more damage to the cambium after shorter exposure to the heat source than Quercus species. In all the species studied, time to reach lethal temperatures in the cambium was dependent on thickness rather than on flammability of the bark. The study findings revealed that tree species may influence flammability of mixed fuels disproportionately to their load. The studied species showed to exert a contrasted effect on flammability of the mixtures, increasing ignitability and decreasing combustibility and consumability well out of their proportion in the mixture. This may potentially influence fire dynamics in mixed forests