Hymenoscyphus albidus is not associated with an anamorphic stage and displays slower growth than Hymenoscyphus pseudoalbidus on agar media

Examination of isolates of Hymenoscyphus albidus from France revealed that this fungus does not form an anamorphic stage in culture. The lack of an asexual stage in this fungus is a conspicuous morphological difference to the ash dieback pathogen Hymenoscyphus pseudoalbidus, which is associated with its Chalara fraxinea anamorphic state. In growth studies on malt extract agar (MEA) and MEA amended with ash leaflets (ash leaf malt extract agar, AMEA) at 20°C, isolates of H. albidus grew slower than those of H. pseudoalbidus. On AMEA, the growth of cultures of both species was greatly enhanced.     

The decay pattern of Phellinus tremulae (Bond.) Bond,et Borisov in Populus tremula L.

The distribution of Phellinus tremulae in stems of Populus tremula was studied visually, macroscopically as well as microscopically, and by means of isolation of the fungus in pure culture. Evidence suggests that P. tremulae occurs alone in most of the tree. Microorganisms associated with P. tremulae in the wood are suggested to be independent invaders or secondary invaders. A dark reaction zone was formed in certain parts of the wood and consisted microscopically of melanized hyphes and brown material in the ray cells. An inner wood, formed as a result of the death of nearby brandies, is apparently the main part infected by P. tremulae, and its outer border may basically limit the spread of the fungus in the trunk. The formation of “heartwood” in aspen is discussed, and a suggested outline shown for the infection and decay processes caused by the fungus.     

Effect of inoculation with ecto- and arbuscular mycorrhizae and Rhizobium on the growth and nitrogen fixation by black locust,Robinia pseudoacacia

Experiments were made to determine the effect of inoculation withRhizobium, the ectomycorrhizal fungus Hebelomamesophasem and the arbuscular mycorrhizal fungus Glomuscaledonium on the growth and nitrogen fixation of black locust(Robinia pseudoacacia Linn.) seedlings grown invitro and in pot culture. The results showed that both mycorrhizalfungi and Rhizobium stimulated the growth and nitrogenfixing ability of inoculated seedlings. Inoculation with all three microbestogether produced the most beneficial effects on nitrogen fixation, mycorrhizaldevelopment and seedling growth.     

A medium to enhance identification of Septoria musiva from poplar cankers

A series of experiments was conducted to determine the relative tolerance in vitro of an isolate of Septoria musiva (a fungus that causes a severely damaging stem canker disease of poplars) for selected chemicals. Inhibition of diameter growth of this fungus on a V‐8 vegetable juice‐based medium with captan, chlorothalonil, iprodione, mancozeb and streptomycin sulphate at concentrations, respectively, of 50, 1, 10, 10, and 100 mg l^–1 was relatively low compared to inhibition of eight other fungi cultured from cankers on poplars. In addition, the presence of captan stimulated profuse sporulation of the fungus. These properties assisted in the identification of S. musiva from cankers resulting from artificial inoculation of poplar branches in the field.     

Stimulation of Armillaria ostoyae vegetative growth by tryptophol and rhizomorph produced by Zygorhynchus moelleri

Tryptophol (an indole-3-ethanol analogue which is a major secondary metabolite produced by Zygorhynchus moelleri) stimulated the growth of 13 out of 18 isolates of Armillaria ostoyae in culture. Rhizomorph production of 16 out of 18 isolates of A. ostoyae was enhanced by the presence of Z moelleri in oak branch segments. Tryptophol can be considered as a growth-promoting substance stimulating the vegetative growth of A. ostoyae in culture, and Z. moelleri as a fungus stimulating the rhizomorph formation on oak wood.     

Economic significance of the infection of beech forests by Hypoxylon deustum (Hoffm. et Fr.) Grev. at Sara Mountain

The fungus Hypoxylon deustum, which is destructive to beech, has been studied. Its spread in beech forests has been examined in detail. Parts of the beech trunks infected with this fungus have been analyzed and the damage to the forest economy has been estimated. In field experiments, beech trees have been infected with mycelia, ascospores and conidia of Hypoxylon deustum in order to investigate their pathogenic properties.     

Comportement in vitro du Sparassis crispa Wulf. ex Fr. et du Sparassis laminosa Fr

Behaviour in vitro of Sparassis crispa Wulf. ex. Fr. and Sparassis laminosa Fr . Sparassis crispa and S. laminosa are described in culture following the method used by Nobles. S. crispa is a very active wood destroying fungus in blocks of Douglas fir (sapwood and heartwood) in laboratory tests. The cauliflower-like fructifications are easily produced on malt-agar and could be produced on a large scale.     

Experimental testing of rust fungus‐mediated herbivory resistance in Betula pendula

Correlative evidence suggests that pathogenic leaf rust fungus, Melampsoridium betulinum, in late summer may negatively affect folivorous insects in the following summer. Correlative association does not necessarily, however, reveal causality. Alternatively, other interconnected plant characters may determine rust densities and herbivore performance. In this study, we used birch clones and rust fungus inoculations to manipulatively test the effects of birch rust and birch genotypes on the growth performance of folivorous moth larvae of Epirrita autumnata (Lep. Geometridae) in the subsequent year. The inoculation treatment increased rust densities (three‐ to 60‐fold) compared with natural infection levels. E. autumnata performance varied among birch clones and showed 4% lower growth performance on rust‐inoculated trees. However, the larval performance did not differ between rust‐treated shoots and untreated control shoots and the use of tree‐specific rust densities as a covariant in statistical analyses failed to reveal any negative association between rust fungus and larval performance. As the slight difference in larval growth performance also levelled until pupation, we propose that rust infection has biologically insignificant importance to the performance of E. autumnata.     

Salt tolerance of the mycorrhizal fungus Cenococcum graniforme (Sow.) Ferd

The ectomycorrhizal fungus Cenococcum graniforme was cultivatcd in modificd Mclin Narkrans liquid medium with varying amounts of soduim chloride to study its salt tolerance. The offcct on moisturc stress due to NaCl conccntration was calculated after Lang (1967). Thc maximum salt tolcrance of the fungus was up to 11 g NaCl per liter. Growth failure of the fungus occurred at 13 g. As the most salty soils of dry rcgions have less than 6 or 8 g NaCl pcr litre of solution, the growth and developmcnt of C. graniforme in arid regions is mosc promising in afforestations in which the trec species are associated in mycorrhizal symbiosis with this fungus.     

Induced resistance of Norway spruce,variation of phenolic compounds and their effects on fungal pathogens

Three clones of Norway spruce (Picea abies) were studied for their response to mass‐inoculation with the blue‐stain fungus Ceratocystis polonica. The effect of different pretreatments (fungal inoculation and wounding) before mass‐inoculation was investigated for their possible role in an acquired resistance reaction. Pretreated trees showed enhanced resistance to the subsequent mass‐inoculation relative to control trees that received no pretreatment. Furthermore, the fungal colonization of inoculated trees was less than that of wounded trees. The phenolic content of the bark, analysed by RP‐HPLC, was compared in trees receiving different treatments. Trees inoculated with C. polonica had higher average concentration of (+)‐catechin, taxifolin and trans‐resveratrol than wounded trees. Both inoculated and wounded trees had higher average concentrations of these compounds than control trees. The effect of the phenolic extract of Norway spruce bark on the growth of the root rot fungus Heterobasidion annosum and the blue‐stain fungi C. polonica and Ophiostoma penicillatum were investigated in vitro. Heterobasidion annosum was not negatively affected, and the extracts had fungistatic effects on the blue‐stain fungi. The growth of O. penicillatum was more inhibited than the growth of the more aggressive C. polonica.     

Role of Phialemonium curvatum as a potential biological control agent against a blue stain fungus on aspen

Ophiostoma crassivaginatum is the most important blue stain fungus on Populus tremuloides and causes considerable reduction in the value of the end product. The effect of a hyphomycetous fungus, Phialemonium curvatum, on the in vitro growth and wood chip colonization by O. crassivaginatum was studied. The in vitro growth of O. crassivaginatum was significantly inhibited when grown in dual culture or when treated with culture filtrate of P. curvatum. Ophiostoma crassivaginatum failed to colonize P. tremuloides wood chips when they were pre-inoculated with mycelial suspension of P. curvatum. The potential use of P. curvatum as a biological control agent against O. crassivaginatum is suggested.     

Genetic resistance to Hymenoscyphus pseudoalbidus limits fungal growth and symptom occurrence in Fraxinus excelsior

The European common ash (Fraxinus excelsior) is currently threatened by a pathogenic fungus, Hymenoscyphus pseudoalbidus, which seems to enter the trees through the leaves. Continuous assessments of 39 clones in Danish field trials have shown that there are significant differences in the susceptibility of clones to the new disease. Interestingly, clones that showed early leaf senescence in the autumn were in general less susceptible to the disease than late‐senescing clones. Thus, variation in susceptibility could be owing to phenological differences associated with the infection biology. To test whether differences in susceptibility are driven by genetically based factors other than phenology, we compared inoculations with H. pseudoalbidus on four highly susceptible clones with those of four less susceptible clones. Development of necrosis was hereafter followed regularly. The growth of the fungus in the inner bark was further detected with species‐specific PCR primers. The severity of the response to infection shows significant differentiation among clones and significant correlation with clone susceptibility, as assessed from natural infections in field trials. The fungus was detected in tissues immediately surrounding the necrosis but showed some signs of endophytic growth. The results suggest that healthier clones are able to limit the growth and spread of the fungus and thereby minimize the occurrence of symptoms. This gives hope for the future preservation of F. excelsior in Europe through selection and breeding.     

Studies on ectomycorrhizae of pine

Infection of feeder roots of Pinus echinata by the ectomycorrhizal fungus, Pisolithus tinctorius, resulted in an approximate 40-fold increase in the level of 3-carene, and Ccnococcum graniforme induced an approximate 30-fold increase in β-phellandrene. Vapors of these volatile compounds affected the vegetative growth of different ectomycorrhizal and root pathogenic fungi to different degrees in laboratory experiments.     

Hebeloma inoculation on Norway spruce seedlings in solarized and infested soil

The effect of inoculation of Hebeloma sp. on the growth of Norway spruce (Picea abies) seedlings was studied, in a controlled environment, with soil samples naturally infested by Pythium spp., Fusarium spp. and Rhizoctonia solani, and with samples of soil in which the pathogens had been controlled by solarization. The best results were obtained in solarized soil, but mycorrhizae also enhanced plant growth in the presence of the whole soil-borne mycoflora. The combined use of inoeulation of a mycorrhizal fungus and solarization is discussed.     

The impact of cronartium flaccidum on the growth of pinus sylvestris

The blister rust of two‐needle pines in Europe is caused by the rust fungus, Cronartium flaccidum (Alb. Schw.) Wint. There are two races of the fungus: One host‐alternating and another pine‐to‐pine race. The latter race is considered to be more common in northern Sweden. The impact of this rust on growth of Scots pine (Pinus sylvestris L.) was investigated in three selected stands in northern Sweden. Radial stem increment was reduced 40–70% by severe attacks and 20–40% by minor attacks. The reduction of stem volume growth was probably greater. The faster growing trees seemd to be more severely attacked. Trees growing on poor soils appeared to lose almost as much growth capacity from a minor attack as from a severe attack.     

Growth, nitrogen fixation and mineral acquisition of Alnus sieboldiana after inoculation of Frankia together with Gigaspora margarita and Pseudomonas putida

The role of tetrapartite associations among Frankia, Gigaspora margarita (an arbuscular mycorrhizal fungus), Pseudomonas putida (rhizobacterium), and Alnus sieboldiana in growth, nitrogen fixation, and mineral acquisition of A. sieboldiana was investigated. Seedlings of A. sieboldiana were inoculated with Frankia isolated from root nodules of alder, followed by inoculation of G. margarita and P. putida, and were grown for 5 months in a greenhouse. The seedlings inoculated with Frankia and G. margarita together produced the highest biomass of shoots and root nodules. Nitrogen-fixation activity, measured by acetylene reduction assay, was observed when Frankia was inoculated. The activity, on a per-nodule gram basis, decreased after G. margarita inoculation, but on a per-plant basis there was no significant difference in the activity among inoculation treatments. The mineral content in the seedlings changed after inoculation with Frankia, but not after inoculation with P. putida and/or G. margarita. The results showed a synergistic interaction among Frankia, the mycorrhizal fungus, and the rhizobacterium on the growth of A. sieboldiana.     

First report of Erysiphe kenjiana causing powdery mildew of elm in Romania

Erysiphe kenjiana is an Asian fungus causing powdery mildew of Ulmus spp. In 2017, 10 years after its introduction in Europe, it was detected in Romania on Ulmus pumila, the Siberian elm, which is cultivated in urban environments as an ornamental and shade tree. The identification of the fungus was based on morphological characteristics and molecular data (rDNA internal transcribed spacer region). This is the first report of E. kenjiana in Romania, and only the third from a European country.     

Chemical factors in Pinus strobus inhibitory to Armillaria ostoyae

Fresh sapwood of Pinus strobus inhibited the growth of Armillaria osotyae. Compounds extracted from sapwood with ethyl acetate inhibited the fungus in bioassays. Pinosylvin monothyl ether as tentatively identified by thin layer chromatography and ultraviolet spectra was isolated from the extract and found to inhibit the growth of A. ostoyae.     

Genetic diversity and population structure of Raffaelea quercus‐mongolicae,a fungus associated with oak mortality in South Korea

Raffaelea quercus‐mongolicae is a fungus associated with oak wilt and deemed to cause extensive oak mortality in South Korea. Since the discovery of this fungus on a dead Mongolian oak (Quercus mongolica) in 2004, the mortality continued to spread southwards in South Korea. Despite continued expansion of the disease and associated significant impacts on forest ecosystems, information is lacking about the origin and genetic diversity of R. quercus‐mongolicae. Restriction‐site‐associated DNA (RAD) sequencing was used to assess genetic diversity and population structure among five populations (provinces) of R. quercus‐mongolicae in South Korea. In total, 179 single nucleotide polymorphisms (SNPs) were identified among 2,639 RAD loci across the nuclear genome of the 54 R. quercus‐mongolicae isolates (0.0012 SNPs per bp), which displayed an overall low expected heterozygosity and no apparent population structure. The low genetic diversity and no apparent population structure among South Korean populations of this ambrosia beetle‐vectored fungus support the hypothesis that this fungus was introduced to South Korea.