First report of Mycopappus alni in Japan: species identification of the pathogenic fungus of a frosty mildew disease in Crataegus chlorosarca

A leaf disease similar to frosty mildew disease caused by Mycopappus species was detected on the leaves of Crataegus chlorosarca in Tomakomai, Hokkaido Prefecture. From morphological observations and gene analyses of rDNA-ITS, the fungus was identified as M. alni, which causes leaf blight disease on Alnus spp., Betula spp., and a Pyrus sp. in North America and Turkey. This is the first report of M. alni in Japan and Crataegus as its new host genus.     

Powdery Mildew Caused by an Erysiphe sp. on Korean Ginseng

In August and September 2014, Korean ginseng (Panax ginseng) plants showing symptoms of powdery mildew infection were found in a polyethylene film‐covered greenhouse in Suwon, Korea. The mildew was initially observed to occur in circular to irregular white colonies, which subsequently developed into abundant mycelial growths on both leaf surfaces. No chasmothecia were observed. Based on its morphological characteristics, the fungus was determined to be a species of Erysiphe. Phylogenetic analysis of the sequence of the internal transcribed spacer region of the ribosomal DNA obtained from the isolate placed the powdery mildew fungus in the genus Erysiphe. Here, we describe this Erysiphe sp. found growing on Korean ginseng using both illustrations and molecular data. A comparison of the Korean isolate and three previous records of powdery mildews known to grow on Panax plants is also provided. This is the first report of powdery mildew on Korean ginseng in Korea.     

Attraction and oviposition responses of the fungus gnat Bradysia impatiens to microbes and microbe‐inoculated seedlings in laboratory bioassays

Laboratory tests were conducted to examine preferences of Bradysia impatiens Johannsen (Diptera: Sciaridae) larvae and adults for various microbes associated with greenhouse crops. Fungus gnat larvae and adults exhibited a preference for cultures of Pythium spp. over the medium used to grow the pathogens. Larvae also exhibited a preference for geranium seedlings infected with pathogenic Pythium spp. [P. aphanidermatum (Edson) Fitz., P. ultimum Trow, and P. irregulare Buis. (Oomycota: Peronosporales)] over non‐inoculated plants. Adult fungus gnats exhibited a strong ovipositional preference for the aforementioned Pythium spp. as well as a variety of other microorganisms, including the pathogenic fungus Thielaviopsis basicola (Berk. & Br.) (Ascomycota: Microascales), the geranium‐infecting bacterium Xanthomonas campestris pv. pelargonii (Brown) Dye (Proteobacteria: Xanthomonadales), the non‐pathogenic species Pythium torulosum Coker & P. Patt. and Pythium graminicola Subramaniam, the pathogen‐suppressive fungus Trichoderma harzianum Rifai (Ascomycota: Hypocreales), and the insect pathogenic fungus Beauveria bassiana (Balsamo) Vuillemin (Ascomycota: Hypocreales). Our study is the first to demonstrate that fungus gnats are attracted to and/or stimulated to oviposit by a wide array of living microorganisms both in pure culture and in association with plant seedlings. These findings have important implications with respect to the potential role of fungus gnats in plant pathogen transmission.     

Mycopappus quercus sp. nov., causing frosty mildew inQuercus acutissima

The causal fungus of frosty mildew inQuercus acutissima was taxonomically studied. Brown spots with conical white to yellowish tufts of the causal, fungus developed on the leaves, followed by successive defoliation. The fungus was regarded as a new species ofMycopappus, M. quercus, from the morphology of the multicellular propagules. The ascogenous stage and true conidia of the fungus were not observed, although sclerotia were formed on the fallen diseased leaves.     

A novel strain of Pseudozyma aphidis from mulberry parasitises the conidia of mulberry powdery mildew fungus Phyllactinia sp. and its biocontrol effect in the fields

Plant surface is colonised with a vast community of non-pathogenic epiphytic microorganisms which play an important role in host defence. In the present study, we reported a fungus from mulberry leaf surface that showed an antagonistic effect against mulberry powdery mildew fungal pathogen Phyllactinia sp. This novel isolate is a yeast-like fungus that was identified as Pseudozyma aphidis CNm2012 based on morphologic and phylogenetic analysis. According to our research, P. aphidis CNm2012 directly acted on the powdery mildew conidia via parasitism which caused conidial atrophy, collapse and eventually, cleavage and death. During the parasitic process, we found the isolate could gather around the conidia of Phyllactinia sp. and form hyphae that grew on the conidial surface and utilise the conidia as a nutrient source. Field studies revealed that P. aphidis CNm2012 could suppress the disease incidence of mulberry powdery mildew caused by Phyllactinia sp., and reduce the disease severity. To our knowledge, it is the first report of P. aphidis directly against powdery mildew fungus Phyllactinia spp. by parasitism. Our results indicated that P. aphidis CNm2012 could be served as an environmentally friendly alternative of chemical pesticides to manage mulberry powdery mildew disease.     

Mycosphaerella chaenomelis sp. nov.: The teleomorph ofCercosporella sp., the causal fungus of frosty mildew inChaenomeles sinensis, and its role as the primary infection source

A leaf spot disease called frosty mildew was observed onChaenomeles sinensis throughout Japan. Small brown spots with white tufts occurred followed by successive defoliation. On the fallen leaves, minute black dots are formed. The causal fungus was regarded as a new species ofMycosphaerella, M. chaenomelis, andCercosporella chaenomelis in anamorph. Pathogenicity of the fungus was confirmed only inC. sinensis by inoculation experiments. Colonies of the fungus grew well on potato sucrose agar, and grew at 10–30°C with an optimum temperature of 25°C. The fungus overwintered on the fallen diseased leaves in the form of pseudothecia, and ascospores served as the primary infection source from April to June.     

The potential for Entomophaga maimaiga to regulate gypsy moth Lymantria dispar (L.) (Lepidoptera: Erebidae) in Europe

Gypsy moth, Lymantria dispar L., is one of the most important pests of deciduous trees in Europe. In regular cycles, it causes large‐scale defoliation mostly of oak, Quercus spp., forests. Government authorities in the most infested countries in Europe conduct large‐scale applications of pesticides against gypsy moth. In 1999, a new natural enemy, the entomopathogenic fungus Entomophaga maimaiga, was successfully introduced into a gypsy moth population in Bulgaria. Recent investigations suggest that now E. maimaiga is quickly spreading in Europe. Herein, past studies are reviewed regarding this fungus with special emphasis on its potential for becoming an important factor regulating gypsy moth populations in Europe, focusing on the host's population dynamics in relation to the fungus, the influence of environmental conditions on fungal activity, the influence of E. maimaiga on the native entomofauna, including other gypsy moth natural enemies, and spread of the fungus. Based on this analysis, the potential of E. maimaiga for providing control in European gypsy moth populations is estimated.     

Non‐pollinating Fig Wasps Decrease Pollinator and Seed Production in Ficus andicola (Moraceae)

Fig trees ( Ficus spp.) and Agaonine fig‐wasps participate in an obligate mutualism. Fig wasps can only develop within fig inflorescences (syconia) and they are the only organisms capable of pollinating fig flowers. Other non‐pollinating wasps that lay eggs by inserting their ovipositors from the outside can also develop in syconia. These parasitic wasps may be parasitoids of either pollinating or other non‐pollinating wasps, or form galls in fig flowers or other tissues. Depending on this interaction, parasitic wasps may have various effects on the production of pollinating wasps and seeds. Wasps in the genus Idarnes, which parasitize New World figs (subgenus Urostigma), have an effect on wasp production but not on seed production. Heterandrium spp., which have short ovipositors and lay on external flowers, are infrequent and no effect on seed production has been documented. In the Colombian Andes, Idarnes spp. and Heterandrium spp. are the most frequent parasites of the Ficus andicola — Pegoscapus sp. mutualism, affecting 62 and 43 percent of syconia, respectively. Controlling for other factors that influence wasp and seed production, such as number of foundresses, syconium size and tree, we found that Idarnes reduced pollinator production by almost half but did not reduce seed production, whereas Heterandrium reduced seed production by 40 percent, and marginally affected pollinator production. Our results provide the first clear documentation of Heterandrium spp. impact on fig seed production. Whether the relative abundance of this genus is a generalized phenomenon in montane forest remains to be determined.     

Genetic dissection of a TIR‐NB‐LRR locus from the wild North American grapevine species Muscadinia rotundifolia identifies paralogous genes conferring resistance to major fungal and oomycete pathogens in cultivated grapevine

The most economically important diseases of grapevine cultivation worldwide are caused by the fungal pathogen powdery mildew (Erysiphe necator syn. Uncinula necator) and the oomycete pathogen downy mildew (Plasmopara viticola). Currently, grapegrowers rely heavily on the use of agrochemicals to minimize the potentially devastating impact of these pathogens on grape yield and quality. The wild North American grapevine species Muscadinia rotundifolia was recognized as early as 1889 to be resistant to both powdery and downy mildew. We have now mapped resistance to these two mildew pathogens in M. rotundifolia to a single locus on chromosome 12 that contains a family of seven TIR‐NB‐LRR genes. We further demonstrate that two highly homologous (86% amino acid identity) members of this gene family confer strong resistance to these unrelated pathogens following genetic transformation into susceptible Vitis vinifera winegrape cultivars. These two genes, designated r esistance to P lasmopara v iticola (MrRPV1) are the first resistance genes to be cloned from a grapevine species. Both MrRUN1 and MrRPV1 were found to confer resistance to multiple powdery and downy mildew isolates from France, North America and Australia; however, a single powdery mildew isolate collected from the south‐eastern region of North America, to which M. rotundifolia is native, was capable of breaking MrRUN1‐mediated resistance. Comparisons of gene organization and coding sequences between M. rotundifolia and the cultivated grapevine V. vinifera at the MrRUN1/MrRPV1 locus revealed a high level of synteny, suggesting that the TIR‐NB‐LRR genes at this locus share a common ancestor.     

Physicochemical tolerance,habitat use and predation are drivers of patterns of coexistence and exclusion among invasive and resident amphipods

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Bioassay‐Guided Isolation of Antifungal Compounds from Disporopsis aspersa (Hua) Engl. ex Diels against Pseudoperonospora cubensis and Phytophthora infestans

Oomycetes are one type of the most highly destructive of the diseases that cause damage to some important crop plants, such as potato late blight, cucumber downy mildew, and grape downy mildew. As main approach of the ongoing search for new botanical fungicide from plant, the secondary metabolites of D. aspersa were investigated. Through efficient bioassay‐guided isolation, two new ( 1 and 2 ) and 12 known compounds ( 3  –  14 ) were isolated, and their structures were determined via extensive NMR, HR‐ESI‐MS, and IR. They were isolated from this genus for the first time except for compounds 11 and 12 . The biological properties of 1  –  14 were evaluated against Pseudoperonospora cubensis and Phytophthora infestans. Compounds 1  –  8 showed potent antifungal activity in vitro. Additionally, compound 3 has preferable control effect on cucumber downy mildew, showing dual effect of protection and treatment in vivo.     

Molecular phylogenetic analyses reveal a close relationship between powdery mildew fungi on some tropical trees and Erysiphe alphitoides, an oak powdery mildew

To investigate the phylogenetic relationships among the powdery mildew fungi of some economically important tropical trees belonging to Oidium subgenus Pseudoidium, we conducted molecular phylogenetic analyses using 30 DNA sequences of the rDNA internal transcribed spacer (ITS) regions and 26 sequences of the domains D1 and D2 of the 28S rDNA obtained from the powdery mildews on Hevea brasiliensis (para rubber tree), Anacardium occidentale (cashew), Bixa orellana, Citrus spp., Mangifera indica (mango), and Acacia spp. The results indicate that the powdery mildew fungi isolated from these tropical trees are closely related to one another. These powdery mildews are also closely related to E. alphitoides (including Erysiphe sp. on Quercus phillyraeoides). Because of the obligate biotrophic nature of the powdery mildew fungi, the relationship between powdery mildews and their host plants is conservative. However, the present study suggests that a particular powdery mildew species has expanded its host ranges on a wide range of the tropical trees. This article also suggests that a powdery mildew fungus distributed in temperate regions of the Northern Hemisphere expanded its host ranges onto tropical plants and may be a good example of how geographical and host range expansion has occurred in the Erysiphales.     

Rye Pm8 and wheat Pm3 are orthologous genes and show evolutionary conservation of resistance function against powdery mildew

The improvement of wheat through breeding has relied strongly on the use of genetic material from related wild and domesticated grass species. The 1RS chromosome arm from rye was introgressed into wheat and crossed into many wheat lines, as it improves yield and fungal disease resistance. Pm8 is a powdery mildew resistance gene on 1RS which, after widespread agricultural cultivation, is now widely overcome by adapted mildew races. Here we show by homology‐based cloning and subsequent physical and genetic mapping that Pm8 is the rye orthologue of the Pm3 allelic series of mildew resistance genes in wheat. The cloned gene was functionally validated as Pm8 by transient, single‐cell expression analysis and stable transformation. Sequence analysis revealed a complex mosaic of ancient haplotypes among Pm3‐ and Pm8‐like genes from different members of the Triticeae. These results show that the two genes have evolved independently after the divergence of the species 7.5 million years ago and kept their function in mildew resistance. During this long time span the co‐evolving pathogens have not overcome these genes, which is in strong contrast to the breakdown of Pm8 resistance since its introduction into commercial wheat 70 years ago. Sequence comparison revealed that evolutionary pressure acted on the same subdomains and sequence features of the two orthologous genes. This suggests that they recognize directly or indirectly the same pathogen effectors that have been conserved in the powdery mildews of wheat and rye.     

Complex interactions between bacteria and haemosporidia in coinfected hosts: An experiment

1. Hosts are typically coinfected by multiple parasite species whose interactions might be synergetic or antagonistic, producing unpredictable physiological and pathological impacts on the host. This study shows the interaction between Plasmodium spp. and Leucocytozoon spp. in birds experimentally infected or not infected with Mycoplasma gallisepticum.
2. In 1994, the bacterium Mycoplasma gallisepticum jumped from poultry to wild birds in which it caused a major epidemic in North America. Birds infected with M. gallisepticum show conjunctivitis as well as increased levels of corticosterone.
3. Malaria and other haemosporidia are widespread in birds, and chronic infections become apparent with the detectable presence of the parasite in peripheral blood in response to elevated levels of natural or experimental corticosterone levels.
4. Knowing the immunosuppressive effect of corticosterone on the avian immune system, we tested the hypothesis that chronic infections of Plasmodium spp. and Leucocytozoon spp. in house finches would respond to experimental inoculation with M. gallisepticum as corticosterone levels are known to increase following inoculation.
5. Plasmodium spp. infection intensity increased within days of M. gallisepticum inoculation as shown both by the appearance of infected erythrocytes and by the increase in the number and the intensity of positive PCR tests.
6. Leucocytozoon spp. infection intensity increased when Plasmodium spp. infection intensity increased, but not in response to M. gallisepticum inoculation. Leucocytozoon spp. and Plasmodium spp. seemed to compete in the host as shown by a negative correlation between the changes in their PCR score when both pathogens were present in the same individual.
7. Host responses to coinfection with multiple pathogens measured by the hematocrit and white blood cell count depended on the haemosporidian community composition. Host investment in the leukocyte response was higher in the single‐haemosporidia‐infected groups when birds were infected with M. gallisepticum.
8. A trade‐off was observed between the immune control of the chronic infection (Plasmodium spp./Leucocytozoon spp.) and the immune response to the novel bacterial infection (M. gallisepticum).

     

Foliar δ13C response patterns along a moisture gradient arising from genetic variation and phenotypic plasticity in grassland species of Inner Mongolia

Plants depend upon both genetic differences and phenotypic plasticity to cope with environmental variation over different timescales. The spatial variation in foliar δ¹³C levels along a moisture gradient represents an overlay of genetic and plastic responses. We hypothesized that such a spatial variation would be more obvious than the variation arising purely from a plastic response to moisture change. Leymus chinensis and Stipa spp. were sampled from Inner Mongolia along a dry‐wet transect, and some of these species were transplanted to an area with a moisture gradient. For Stipa spp., the slope of foliar δ¹³C and mean annual precipitation along the transect was significantly steeper than that of foliar δ¹³C and mean annual precipitation after the watering treatment. For L. chinensis, there was a general decreasing trend in foliar δ¹³C under the different (increasing) watering levels; however, its populations showed an irregular relationship between foliar δ¹³C and moisture origin. Therefore, support for our hypothesis was obtained from Stipa spp., but not from L. chinensis.     

Redheadia quercus gen. et sp. nov., the teleomorph of Mycopappus quercus, the frosty mildew fungus in Quercus acutissima

The teleomorph of Mycopappus quercus causing frosty mildew in Quercus acutissima is described as a new genus and species, Redheadia quercus, in the Sclerotiniaceae. Apothecia sprout from sclerotia on the fallen infected leaves kept for 10 months at 5°C and subsequent incubation at 15°C under diffused room light. Typical zonate lesions and multicellular propagules of M. quercus are produced on Q. acutissima, by mycelial inoculation using an isolate from a single ascospore, confirming the teleomorph–anamorphic connection. No significant differences are observed between cultured colonies of isolates from the ascospore and those from the propagule. Sclerotia and microconidia of the fungus are produced on culture media.     

First Report of Myrothecium roridum Causing Leaf Spot on Anthurium andraeanum in China

A new severe disease on Anthurium andraeanum Lind. was observed in the summer of 2011 in Beijing, China. The fungus was isolated from symptomatic leaves, and its pathogenicity was confirmed. Based on the morphological characteristics and molecular analysis, the pathogen was identified as Myrothecium roridum Tode ex Fr. This is the first report of M. roridum causing leaf spot on A. andraeanum in China.