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Snow mold investigations were made since last century in the European part of the former USSR and the Urals. At the beginning of this century, we organized a number of Russian–Japanese expeditions in Russia to investigate sclerotial snow mold fungi inhabiting different winter conditions. These expeditions have extended distribution areas of Typhula ishikariensis, Sclerotinia borealis, and S. nivalis. T. ishikariensis was first found in the Asian part of the country, i.e., the Urals, Western Siberia, Eastern Siberia, and the Far East. We were the first to record T. ishikariensis species II in the Far East and Eastern Siberia. S. borealis was observed wherever freezing predisposed plants. S. nivalis was first recorded both in European and Asian parts of Russia. We assume that the previously described species such as S. sativa, S. bulborum, and S. intermedia are synonymous with psychrotolerant S. nivalis, but not with mesophilic S. minor. This chapter briefly describes other snow mold fungi such as Microdochium nivale, Sclerotinia trifoliorum, Phacidium infestans, Pythium spp., Typhula incarnata, T. phacorrhiza, and Sclerotium nivale since they were not our main interest of research.

Speckled snow mould (caused by Typhula ishikariensis) is a potential threat to winter wheat (Triticum aestivum L.) production in eastern Canada. Information on the inheritance of snow mould resistance is needed to develop an effective breeding strategy. In this study, the inheritance of resistance to the speckled snow mould was examined using crosses of a resistant genotype, PI 173438, and four susceptible cultivars, Lennox, Kitami-2, Norin-8 and Ena. The parental lines, and the F1 and F2 populations from each of the four crosses were grown in the field and in an unheated plastic greenhouse and scored for snow mould resistance. Biomass yield, survival, plant height and number of tillers/plant, all expressed as percentage of check plants, were used as indices of snow mould resistance. Generation means analysis, combining data from the field and greenhouse experiments, indicated that snow mould resistance was largely influenced by environmental conditions, and that additive genetic effects were more important than epistatic effects in controlling the expression of the disease. Dominance effects oriented towards susceptibility were detected in only one of the four crosses. Estimates of broad sense heritability in the four F2 populations ranged from 0.62 to 0.96 and from 0.34 to 0.79, respectively, when biomass yield and number of tillers/plant were used as indices of snow mould resistance. When plant height was used as an index of snow mould resistance, the heritability estimates ranged from 0.10 to 0.53. Key words: Wheat (winter), Triticum aestivum, speckled snow mould, Typhula ishikariensis, heritability

Isolates of Typhula ishikariensis, a snow mould fungus, from Norway were divided into three groups, which, although differing in culture morphology and in mating reactions with testers of T. ishikariensis biotypes A and B from Japan, were, at least partially, interfertile. Population structures of this fungus at 23 sites in meadows and pastures were then determined, based on vegetative compatability group. Except for two sites dominated by a single large vegetative compatibility group, populations were generally diverse, regardless of the cropping history of the site.

Light and transmission electron microscopy revealed thatTyphula ishikariensis penetrated into bentgrass leaves either through cuticles or stomata either by single hyphae or infection cushions formed on host surfaces. Time course study on infected leaves showed that penetration through stomatal subsidiary cells and their adjacent cells seemed to occur earlier than that through epidermal cells located farther from stomata. More than 30% of epidermal cells were infected by 10 days after inoculation. When hyphae penetrated through an intact cuticle of epidermal cells, they seemed to dissolve host cell walls enzymatically at penetration sites. Physical pressure also seemed to be involved in penetration.

Fructan structures vary widely among plant species. Graminan-type fructans, extensions of sucrose through β-(2,6)-linked fructosyl units with branches of β-(2,1)-linked fructosyl units, accumulate in tissues of winter wheat (Triticum aestivum) during cold hardening and are metabolized under persistent snow cover. Snow molds such as Typhula ishikariensis and Microdochium nivale opportunistically infect wheat under snow cover. Snow mold-resistant wheat cultivars tend to heavily accumulate and slowly metabolize water-soluble carbohydrates including graminans in comparison with snow mold-susceptible cultivars. We observed time-dependent changes in the amounts of water-soluble carbohydrates in snow mold-inoculated wheat tissues, and accumulated fructan levels significantly decreased as a result of snow mold inoculation and incubation under snow cover, especially in a snow mold-susceptible wheat cultivar. Three candidates for fructan exohydrolase (FEH) cDNAs with high homology to cell wall invertases were isolated from wheat leaf tissues inoculated with snow mold and incubated under snow cover. The substrate specificity of enzymes encoded by the isolated clones was analyzed by recombinant proteins expressed in Pichia pastoris. The recombinant protein (Wfh-sm3m) encoded by one (Wfh-sm3) of the isolated clones preferentially degraded 6-kestotriose and possessed minor hydrolase activity to 1-kestotriose and 1,1-kestotetraose. Moreover, Wfh-sm3m hydrolyzed almost all graminans that accumulated in hardened wheat tissues. Wfh-sm3 transcripts increased in wheat leaf tissues inoculated with snow mold and incubated under snow cover. These results suggest that Wfh-sm3 encodes a 6-FEH with minor 1-FEH activity and is associated with degradation of fructans in wheat leaf tissues during inoculation and incubation under snow cover.

Population structure of Typhula incarnata and Typhula ishikariensis, snow mold fungi, was determined by vegetative incompatibility on agar plates using isolates from 10 sites that differed in the extent of disturbance. Typhula incarnata populations were always diverse, with many different vegetative compatibility groups regardless of habitat differences, whereas diversity of T. ishikariensis populations differed according to habitat. Typhula ishikariensis populations in uncultivated lands were diverse; however, those from agricultural fields planted with perennial grasses became simpler with increasing number of years after the establishment of the host plant community. As a population, isolates from a new habitat were fast growers, less aggressive, and less competitive, and their sclerotia tended to germinate more rapidly than those from an old habitat. Where host plants were annual and the habitat was disturbed annually by tillage, population structure of T. ishikariensis was very simple. These results are discussed in terms of epidemiological differences between the pathogens and the effect of cultivation on population structure change. Key words: Typhula incarnata, Typhula ishikariensis, population structure, disturbance, snow mold fungi.

Improved winter hardiness is an important objective in Norwegian grass breeding. Selection for winter hardiness based on performance in a controlled environment is a means to obtain this goal faster than relying on field trials. Progress in selection will depend on the genetic variation and the heritability of the traits. This investigation shows that artificial screening for winter survival traits reveals significant genetic variation in Dactylis glomerata in all three characters tested: resistance to Fusarium nivale, resistance to Typhula ishikariensis and resistance to freezing. The broad sense heritability of resistance to snow mould fungi between 0.4 and 0.5, and for freezing resistance between 0.5 and 0.7, indicates good possibilities for improving the traits by selection for resistance. The genotypic correlation calculated from the analysis of covariance of two half-sib families was found to be approximately 1. Although associated with contradictory data, this finding supports the theory t...

Low-temperature fungi were collected from plants just after snowmelt, and their antagonistic activity against Typhula ishikariensis, a snow mold fungus, was determined using orchardgrass seedlings. Isolates from gramineous plant debris, considered to beT. phacorrhiza, suppressed the disease caused by T. ishikariensis biotype A or B. Antagonists differed in their effectiveness against these biotypes. Isolates antagonistic to biotype A, which is the principal snow mold of perennial ryegrass in northern Hokkaido, were localized in this district. Despite prolonged snow, susceptible, perennial ryegrass is successfully grown there. These findings suggest the natural occurrence of biological control of the disease in perennial ryegrass pastures in northern Hokkaido. Ground tissues of orchardgrass or alfalfa reduced activities of antagonists when mixed in the inoculum. Plant litter such as fallen maple leaves and rice straw favored antagonism. Application of the antagonists in a naturally infested field planted with perennial ryegrass resulted in an yield increase of 26.5% compared with the untreated control where fall cutting favored the occurrence of snow mold. Where plants were not cut in fall and snow mold damage was slight, yield increase was insignificant.

Resistance to the pathogens of snow mold, especially to Typhula ishikariensis S. Imai is one of the most important traits in wheat breeding for the central region of Hokkaido. T. ishikariensis always occurs in wheat nurseries when snow melts, at Hokkaido Natl.. Agric. Ext. Stn., where the snow mold resistance of winter wheat is being studied. Since T. ishikariensis consists of biotype A, B and C, it is considered that the resistance of winter wheat to each biotype should be determined. T. ishikariensis biotypes A, B and C which were cultured in a vermiculite-wheat bran medium were used as inoculum source. Five wheat varieties, PI 173438 (highly resistant), Horoshirikornugi (resistant), Takunekomugi (moderately resistant), Chihokukomugi (moderately susceptible) and lbis (susceptible) were treated with the inocula after the onset of a continuous snow cover in 1985 and 1986. In the plots inoculated with biotype A, PI 173438 always exhibited higher resistance to the fungi than the other varieties, but the damage of the wheat varieties inoculated with biotype B or C was so serious that the difference in resistance among the wheat varieties could not always be detected (Table 2, 3 and 4). Snow mold damage of wheat varieties inoculated with T.

Tijekom ranog proljeća 2009. na propalim biljkama uljane repice (Brassica napus subsp. napus) uočena je prisutnost mnoštva sklerocija. Laboratorijskim pregledom, izolacijom i determinacijom utvrđeno je da je na mrtvim biljkama prisutna gljiva Typhula ishikariensis. Ova psihrofilna gljiva optimalno raste na niskim temperaturama i uzročnik je tzv. "snježne plijesni" na velikom broju biljnih vrsta. Ukratko je opisana simptomatologija bolesti na uljanoj repici, biologija i ekologija vrste T. ishikariensis, a dan je i kratak osvrt na rizik od pojave snježne plijesni na uljanoj repici u Hrvatskoj.

The change in isolation frequency ofTyphula ishikariensis from bentgrass leaves under snor cover on golf courses near Sapporo, Hokkaido was investigated over three consecutive winters.Agrostis palustris Huds. cv. Penncross growing at these sites was severely infested withT. ishikariensis biotype B. Isolation tests showed thatT. ishikariensis biotype B was first isolated 9 to 34 d after snow cover in December–January, and isolation frequency peaked in February–March. The fungus was never isolated from leaves after snowmelt. The behavior ofT. ishikariensis on bentgrass was discussed in terms of winter hardiness of plants and its epidemiology.

Speckled snow mold, caused by the basidiomycete Typhula ishikariensis Imai, is one of the most prominent winter diseases on perennial grasses and cereal crops in the northern hemisphere. The first linkage map of T. ishikariensis was constructed using a population of 93 sibling monokaryons derived from a single dikaryotic hybrid isolate that was created by a hyphal fusion of two monokaryotic parental isolates. The parental isolates were produced from a pathogenic dikaryotic isolate collected from a golf course in Wisconsin. The two parents exhibit significant differences in the production of aerial mycelium and sclerotia, and in their aggressiveness on creeping bentgrass ( Agrostis stolonifera L.). A total of 251 loci were mapped, comprising 89 inter-simple sequence repeat (ISSR) and 160 random amplified polymorphic DNA (RAPD) markers along with 2 phenotype-based mating-type (MAT) loci. The MAT loci were mapped on linkage groups (LGs) 1 and 7. The markers were evenly distributed over 7 LGs, covering 436 cM with an average marker interval of 2.2 cM. Seven chromosomes were cytologically observed using germ tube bursting methods with acetocarmine staining. This reference linkage map of T. ishikariensis should provide a framework for the mapping of quantitatively controlled traits such as fungal growth, survival, and virulence/avirulence under low temperatures. The map should also be utilized for studying the genome organization of the cold-loving plant-pathogenic Typhula spp. and for comparative genome analysis among fungal taxa.

Isolates of the snow mold fungus, Typhula ishikariensis, were collected from seven localities in northern Japan where snow cover conditions differ. The isolates were identified as T. ishikariensis biotype B, which produces large sclerotia, biotype C with smaller sclerotia, and large sclerotial and intermediate forms. Mating experiments with tester monokaryons indicated that all populations were related. Populations from localities with deep, persistent snow cover produced larger sclerotia, which germinated more readily carpogenically (biotype B and the large sclerotial form) than those from localities where snow cover was shorter and intermittent (biotype C). The aggressiveness of the former was more variable, whereas the latter was without exception aggressive. There was no apparent correlation between growth rate at 0 °C and duration of snow cover. It was concluded that biotype C has been selected for localities with ephemeral snow cover, but that biotypes B and C and the related forms do not form distinct populations and should be regarded as a single taxon.

This study evaluates the effectiveness of four different rates of Wormcast (23 kg, 46 kg, 116 kg and 231 kg/100m2) in comparison to several control treatments in the control of snow mold disease Separate plots were inoculated with Typhula incarnata, Typhula ishikariensis, and Microdochium nivale snow molds. Treatment was applied in the fall before the first snowfall. Phytotoxicity and Biotic plus abiotic injury were measured on a weekly basis one the snow melted till greenup. The highest rates of phytotoxicity were seen in the Wormcast treatment. Plots inoculated with Microdochium nivale saw significant suppression of injury, although higher rates also saw higher rates of disease. Reworks

Six octoploid triticales were compared to hexaploid triticales, wheats and ryes for their reaction to single and combined infection with barley yellow dwarf virus (BYDV) and Typhula ishikariensis Imai. Agronomic characters like winter survival and biomass yield indicated that ryes and wheats are respectively tolerant and susceptible to both diseases. Hexaploid triticales showed a good tolerance to BYDV, but not to T. ishikariensis. Among octoploid lines, reactions to the two pathogens varied from tolerant to susceptible. These results suggest that synthesis of octoploid triticales may provide variability for reaction to both diseases.

Resistance to snow mould fungi is crucial for overwintering crops in northern areas. Only durable resistance for these traits are worthwhile aiming at. Both grasses and cereals have significant variation in resistance. The resistance is regarded as polygenic. The resistance-traits are often confounded by environmental stress factors which can make selection for resistance difficult. Strategies for breeding resistant crops can be natural selection or selection based on testing in controlled environment. Genetic analysis of resistance to both Microdochium nivale and Typhula ishikariensis in half sib families of cocksfoot (Dactylis glomerata) revealed a broad sense heritability close to 0.5 after testing in controlled environment. This indicates good possibilities for progress by selection for resistance. The genotypic correlation between the two traits was found to be 1.0, which means that resistance to the two snow mould species are identical characters. Resistance to snow mould fungi is strongly influenced by cold hardening. The genetic correlation between freezing resistance and snow mould resistance has been found to be close to 1.0 in a limited material of half sib families in cocksfoot. A possible interpretation of this correlation is that the resistance to snow mold fungi is mainly due to the ability of the plant to undergo cold hardening.

Creeping bentgrass (Agrostis stolonifera L.) is currently the most desirable grass for golf courses in temperate climates. In temperate climates, creeping bentgrass is highly susceptible to snow mold fungi which can cause significant injury and mortality. The objectives of this study were to survey a collection of creeping bentgrass clones for reaction to snow mold fungi (Typhula spp.), to identify clones with potential resistance to snow mold fungi, and to identify ecological factors related to necrotic reactions of creeping bentgrass clones to snow mold fungi. Three hundred sixty creeping bentgrass clones, selected from old golf courses in Wisconsin, were evaluated for necrosis reaction during incubation and recovery periods following inoculation with Typhula ishikariensis Imai or as noninoculated controls. Genotypic variation was observed for tolerance to snow mold and cold, dark (noninoculated) conditions but the two tolerances were uncorrelated with each other. Clones from fairways were more tolerant of snow mold, most likely due to long-term natural selection in the absence of fungicide applications. In a second experiment involving 72 selected clones, selection was successful in identifying divergent groups of clones, although differences between experiments indicated that future selection and breeding should make use of multiple inoculation runs. Resistance to snow mold in creeping bentgrass appears to be nonspecific with respect to race and species of snow mold isolates.

(...) The increase in application rate resulted in: 1) a significant decrease in intensity of Typhyla blight, 2) a reduction in time required for turfgrass to recover from injury by pathogenic species of Typhula, 3) an increase in number of sclerotia of T. phacorrhiza recovered from turfgrass thatch, and 4) a decrease in number of sclerotia of T. ishikariensis var. ishikariensis plus T. incarnata recovered from thatch. The intensity of Typhula blight, the time required for turfgrass recovery, and the number of sclerotia of T.i. ishikariensis plus T. incarnata recovered from thatch were significantly reduced in plots of creeping bentgrass that received applications of grain colonized by isolate T016 in 1985 and 1986 compared with that of plots that received applications in 1985 only. (...)

On genetical evidence Typhula FW, T. idahoensis Remsberg, and T. ishikariensis lmai should be considered as one species, and by priority the T. ishikariensis applied to it. Based on morphological characters the following taxonomic ranking is suggested: T. ishikariensis Imai var. ishikariensis, T. ishikariensis Imai var. idahoensis (Remsberg) comb.nov., T.ishikariensis Imai var. canadensis Smith & Årsvoll var.nov.Within this Typhula complex the latter two varieties differ most clearly morphologically, but are most closely related genetically. They are both found only in North America, while var. ishikariensis also occurs in Europe and Asia. Var. canadensis can be distinguished morphologically from the other two varieties by its smaller sclerotia and sporophores, by its more profuse production of aerial mycelium in culture, and the tendency of its sclerotia to be produced in bands, radial rows, and suspended in the aerial mycelium rather than in concentric rings. The only reasonably reliable way of separating the other two varieties is on sclerotial characters. Rind cells of var. idahoensis are more irregular in outline, with more lobate, occasionally digitate cells than var. ishikariensis.

The growth of the snow mould fungi Fusarium nivale (Fr.) Ces. and Typhula ishikariensis Imai at different water potentials was measured on potato dextrose broth supplemented with KCl or polyethylene glycol 6000. The dew point hygrometer method was used for determination of water potentials in both artificial growth media and plant material. Both fungi had a considerable decrease in dry weight production when water potentials of growth media were decreased from −0.7 to −3 MPa. Crown tissue from hardened plants of Phleum pratense L. (timothy, cvs Engmo, Grindstad) and Phalaris arundinacea L. (reed canary grass, cvs Hansvoll, American common, Vantage) showed a significant decrease in water potentials compared with unhardened plants. Thus, reduced availability of water may partly explain increased resistance to fungal pathogens in grasses after hardening.

Soluble sugar content was analysed in plant shoots of winter wheat (Triticum aestivum L. cvs CI 14106, CI 9342, ANB 7143, Starke and Capelle Desprez) cultivated in a growth chamber under simulated winter conditions. The sugar content was analysed five times during the “winter”. In parallel cultivations the plants were infected with a snow mould fungus (Typhula ishikariensis) to test for resistance to this mould. A differentiation in soluble sugar content was found in the winter wheat varieties, which correlated well with their snow mould resistance. A higher content of soluble sugar was related to an increased resistance to snow mould. The connection was found already after three weeks of growth and during the “winter”. A high soluble sugar content may improve the viability of winter wheat infected by snow mould. Determination of soluble sugar content in shoots of winter wheat, cultivated under certain well-controlled climatic conditions, could be a useful test for selection of snow mould resistant varieties. Zusammenfassung Anderungen des loslichen Zuckergehaltes und Resistenz gegenuber Typhula ishikariensis bei Winterweizen Untersucht wurde der losliche Zuckergehalt in Winterweizensprossen (Triticum aestivum L. cvs CI 14106, CI 9342, ANB 7143, Starke und Capelle-Desprez), die von Pflanzen entnommen wurden, die in einer Wachstumskammer unter simulierten Winterbedingungen herangewachsen waren. Der Zuckergehalt wurde an funf Terminen wahrend des simulierten Winters analysiert. Bei parallellaufenden Versuchspflanzen wurde eine Resistenz gegenuber Typhula ishikarienses nach einer kunstlichen Inokulation ermittelt. Festgestellt wurde eine Differenzierung im Zuckergehalt der Winterweizensorten, die mit einer T. ishikariensis-Kesistenz gut korrelierte. Ein hoherer loslicher Zuckergehalt war mit einer hoheren T. ishikariensis-Resistenz gekoppelt. Diese Korrelation konnte schon nach 3wochigem Wachstum festgestellt werden und hat sich wahrend des simulierten Winters bestatigt. Ein hoherer loslicher Zuckergehalt konnte die Lebensfahigkeit von T. ishikariensis-beiallenen Winterweizenpflanzen verbessern. Eine Ermittlung des loslichen Zuckergehalts in Winterweizensprossen, die von Pflanzen unter gut kontrollierten Bedingungen in Wachstumskammern entnommen werden, konnte einen brauchbaren Test bei der Selektion von T. ishikanensis-resistemen Sorten darstellen.

The life-history strategies of Typhula incarnata and T. ishikariensis, the snow mold fungi, were studied in culture experiments. Radial mycelial growth at 0 °C, a temperature at which they thrive under natural conditions, was about half that of growth at the near-optimal temperature, 10 °C. However, when the colonies were covered with unsterile soil, mycelial growth at 0 °C was much greater than at 10 °C. Sclerotium production by T. incarnata was rapid in the latter half of the culture period, and sclerotium maturation was promoted by selected fungi. Typhula incarnata produced sclerotia frequently along the junction with colonies of selected fungi. Typhula ishikariensis biotype A produced the highest percent sclerotial biomass. Sclerotium maturation, i.e., pigmentation, was not stimulated by the selected fungi, but sclerotium production was moderately frequent in dual cultures with them. Typhula ishikariensis biotypes B and C produced the lowest percent sclerotial biomass. Their sclerotium maturation was rapid but not stimulated by the selected fungi. These findings suggest that although these snow mold fungi are, as a whole, stress tolerant, T. incarnata is relatively ruderal, T. ishikariensis biotype A is typically stress tolerant, and T. ishikariensis biotypes B and C are adapted to habitats with high stress and high disturbance.

The resistance of seed-grown plants of Phleum pratense to freezing and to infection by Typhula ishikariensis was considerably enhanced after 2 weeks' exposure to hardening at +1°C. Dehardening of the plants at +12 to 18°C, for 1 or 2 weeks, reduced the freezing resistance significantly. The same treatment did not lead to any decrease in resistance to T. ishikariensis. These observations may indicate that low temperature hardening initiates different mechanisms for resistance to freezing and for resistance to a low temperature pathogen.

Typhula ishikariensis isolates were collected from various parts of Hokkaido. There were two genetically different groups which did not mate with each other; one was termed biotype A, and the other was further divided into two by cultural characteristics, i.e., biotypes B and C. Biotype A was identical to T. ishikariensis and T. ishikariensis var. ishikariensis. Biotype B was not identical to T. idahoensis or T. ishikariensis var. idahoensis. Biotype C was similar to T. ishikariensis var. canadensis. Biotype A tended to occur inland where deep snow cover lasts for a long time. Biotype B was obtained mainly from the coastal regions where snow cover is thin and short in time. The distribution of biotype C was irregular. Taxonomic significance of the genetics and allopatry in the T. ishikariensis complex is discussed.

A previously undescribed, sclerotial, low-temperature-tolerant fungus with orange sclerotia, is common on a wide range of plant species and substrates in Western Canada. It is often associated with snow mold complexes. It has also been found in eastern Canada and Norway, indicating a circumpolar distribution. It is described as Acremonium boreale n.sp. Some isolates were antagonistic towards common snow molds, viz. Fusarium nivale, Sclerotica borealis, Typhula ishikariensis var. ishikariensis and var. canadensis, and the nonsclerotial low-temperature basidiomycete in culture at low temperatures. Although it was weakly parasitic towards two grass species, its main ecological importance seems to be as an invasive primary saprophyte on a wide range of substrates. It may play a significant role in determining the nature and intensity of damage in snow mold complexes.

We identified 16allelesof the A and 17of the B incompatibility factors within 18 dikaryons of T. ishikariensis, a tetrapolar basidiomycete. A 1:1 ratio of alleles of the A and B incompatibility factors was previously reported for T. idahoensis and for T. incarnata.

Survivorship patterns of sclerotia of Typhula incarnata Lasch:Fr. and of T. ishikariensis S. Imai biotype A were compared under field conditions from May to November, using plastic containers with 10- or 250-μm mesh. Minute arthropods always existed in the 250 μm mesh containers, but the difference in mesh size did not affect the viability of sclerotia. Percent viable sclerotia of T. incarnata decreased from 86.0 to 24.2 for those placed on the soil surface, to 5.0% for those buried in soil 81 days after treatment, and then remained the same until the end of the experiment. Most of the T. ishikariensis biotype A sclerotia survived; however, in some containers buried in the soil, half to all of the sclerotia were dead. Several mycoparasites were isolated from both types of sclerotia. The possibility of biological control by reducing the number of sclerotia is discussed in relation to the difference in epidemiology of Typhula incarnata and T. ishikariensis biotype A.