Sooty Blotch And Flyspeck Species Research Articles

Diversity of Sooty Blotch and Flyspeck Fungi on Cider Apples in Spain

Fungi in the sooty blotch and flyspeck (SBFS) complex blemish fruit and reduce the market value of fresh-market apples. In 2010, apples were collected from 16 orchards in northern Spain that had received few to no fungicide sprays. SBFS colonies with the subtending cuticle were excised, pressed, and shipped to Ames, Iowa, United States, for isolation. A total of 213 sequences were aligned after a portion of the rRNA was amplified with primer pair VG9/LR5, and two regions were sequenced with primer pairs ITS1/ITS4 and LROR/LR5. Distance and parsimony analyses of the 28S gene sequences were used to compare the collection with previously isolated SBFS species. Most isolates (89%) were within the subclass Dothideomycetes, order Capnodiales. Within this order, the predominant genus was Schizothyrium (anamorph Zygophiala) (86 isolates), including S. pomi, Z. cryptogama, Z. cylindrica, and two previously undescribed putative species. Also widely prevalent were Microcyclosporella mali (45 isolates), four Microcyclospora spp. (36 isolates), and four Stomiopeltis-like putative species (34 isolates). Seven isolates were within the Eurotiomycetes. Twenty-five putative species were delineated using the ITS sequences and morphological characterization. These included 11 species previously named and reported as members of the SBFS complex, two putative SBFS species that were previously reported but have not yet been described, and 12 newly detected putative SBFS species. The findings add substantially to knowledge of the taxonomic diversity of this ectophytic fungal assemblage in Europe. [Formula: see text] Copyright © 2022 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license .

Peltaster fructicola genome reveals evolution from an invasive phytopathogen to an ectophytic parasite.

Sooty blotch and flyspeck (SBFS) fungi are unconventional plant pathogens that cause economic losses by blemishing the surface appearance of infected fruit. Here, we introduce the 18.14-Mb genome of Peltaster fructicola, one of the most prevalent SBFS species on apple. This undersized assembly contains only 8,334 predicted protein-coding genes and a very small repertoire of repetitive elements. Phylogenomics and comparative genomics revealed that P. fructicola had undergone a reductive evolution, during which the numbers of orphan genes and genes involved in plant cell wall degradation, secondary metabolism, and secreted peptidases and effectors were drastically reduced. In contrast, the genes controlling 1,8-dihydroxynaphthalene (DHN)-melanin biosynthesis and appressorium-mediated penetration were retained substantially. Additionally, microscopic examination of the surfaces of infected apple indicated for the first time that P. fructicola can not only dissolve epicuticular waxes but also partially penetrate the cuticle proper. Our findings indicate that genome contraction, characterized mainly by the massive loss of pathogenicity-related genes, has played an important role in the evolution of P. fructicola (and by implication other SBFS species) from a plant-penetrating ancestor to a non-invasive ectophyte, displaying a novel form of trophic interaction between plants and fungi.

Ancestral state reconstruction infers phytopathogenic origins of sooty blotch and flyspeck fungi on apple

Members of the sooty blotch and flyspeck (SBFS) complex are epiphytic fungi in the Ascomycota that cause economically damaging blemishes of apples worldwide. SBFS fungi are polyphyletic, but approx. 96% of SBFS species are in the Capnodiales. Evolutionary origins of SBFS fungi remain unclear, so we attempted to infer their origins by means of ancestral state reconstruction on a phylogenetic tree built utilizing genes for the nuc 28S rDNA (approx. 830 bp from near the 59 end) and the second largest subunit of RNA polymerase II (RPB2). The analyzed taxa included the well-known genera of SBFS as well as non-SBFS fungi from seven families within the Capnodiales. The non-SBFS taxa were selected based on their distinct ecological niches, including plant-parasitic and saprophytic species. The phylogenetic analyses revealed that most SBFS species in the Capnodiales are closely related to plant-parasitic fungi. Ancestral state reconstruction provided strong evidence that plant-parasitic fungi were the ancestors of the major SBFS lineages. Knowledge gained from this study may help to better understand the ecology and evolution of epiphytic fungi.

Effect of temperature and nutrient concentration on the growth of six species of sooty blotch and flyspeck fungi

Summary. We assessed the effects of temperature and nutrient concentration on the growth of commonly occurring members of the sooty blotch and flyspeck (SBFS) complex in the Midwest United States. Radial growth in vitro of two isolates of each of six SBFS species (Dissoconium aciculare, Colletogloeum sp. FG2, Peltaster sp. P2, Sybren sp. CS1, Pseudocercosporella sp. RH1, and Peltaster fructicola) was measured at 10, 15, 20, 25, 30 and 35°C for 7 weeks. Optimal growth for all six species occurred at 20 to 25°C, with slower growth at 10 and 15°C and little to no growth at �0 or �5°C. Differences in growth rate among species were evident at 10, 15, and 35°C. In a separate trial, the same isolates were incubated at 25°C in darkness on cellulose membrane (12-14 kDa) placed on Noble agar that had been amended to obtain concentrations of 0, 0.01, 0.05 or 0.5% apple juice. After 3 weeks, colonies were digitally photographed and colony opacity was assessed. The presence and concentration of apple juice strongly impacted colony morphology as evidenced by changes in colony tone, and some species were more sensitive to changes in apple juice concentration than others. These findings are the first published evidence of differences among newly described SBFS species in response to temperature and nutrient concentration.

Diversity of the sooty blotch and flyspeck complex on apple in Germany

Sooty blotch and flyspeck (SBFS) is a complex of more than 80 fungal species in 24 genera, mostly belonging to the order Capnodiales within the Dothideomycetes. Colonies of these epiphytes become visible on the surface of apples in mid- to late summer. Several species of SBFS fungi have been previously identified from apples in Germany, but little is known about species diversity, prevalence patterns, or relationship to orchard management practices. To address these questions, apple orchards were surveyed during the 2008 to 2011 seasons in the two largest German apple-growing regions along the Lower Elbe river (northern Germany) and Lake Constance (southern Germany). Using a combination of approaches based on morphology and ITS sequence data, 19 known or putative SBFS species were found, of which 10 belonged to Capnodiales. Abandoned orchards harboured a higher species diversity than organically managed orchards, and no SBFS disease was seen in orchards under integrated pest management. Peltaster cerophilus was the most common SBFS fungus, being associated with 96 and 84 % of SBFS-affected apples sampled from northern and southern German organic orchards, respectively. Microcyclosporella mali and Cyphellophora sessilis were the next most commonly found SBFS species in northern and southern Germany, respectively. Schizothyrium pomi was the only cause of the flyspeck mycelial type of SBFS disease in Germany.

Phenology of Infection on Apple Fruit by Sooty Blotch and Flyspeck Species in Iowa Apple Orchards.

Sooty blotch and flyspeck (SBFS) is a fungal disease complex that can cause significant economic losses to apple growers by blemishing the fruit surface with dark-colored colonies. Little is known about the phenology of host infection for this diverse group of epiphytes. In 2009 and 2010, we investigated the timing of infection of apple fruit by SBFS species in six commercial apple orchards in Iowa. Five trees in each orchard received no fungicide sprays after fruit set. Within 3 weeks after fruit set, 60 apples per tree were covered with Japanese fruit bags to minimize inoculum deposition. Subsequently, a subsample of bagged apples was exposed for a single 2-week-long period and then rebagged for the remainder of the growing season. Experimental treatments included seven consecutive 2-week-long exposure periods; control treatments were apples that were either bagged or exposed for the entire season. After apples had been stored at 2°C for 6 weeks following harvest, all SBFS colonies on the apples were identified to species using a PCR-RFLP protocol. A total of 15 species were identified. For the seven most prevalent species, the number of infections per cm2 of fruit surface was greatest on apples that had been exposed early in the season. Two SBFS species, Peltaster fructicola and Colletogloeopsis-like FG2, differed significantly from each other in time required to attain 50% of the total number of colonies per apple, and analysis of variance indicated a significant interaction of SBFS taxon with exposure period. Our findings are the first evidence of species-specific patterns in timing of SBFS inoculum deposition and infection on apple fruit, and strengthen previous observations that most SBFS infections resulting in visible colonies at harvest develop from infections that occur early in the fruit development period. By defining taxon-specific phenological patterns of fruit infection, our findings, when combined with knowledge of region-specific patterns of taxon prevalence, provide a foundation for development of more efficient and cost-effective SBFS management tactics.

Composition of the sooty blotch and flyspeck complex on apple in Norway is influenced by location and management practices

Sooty blotch and flyspeck (SBFS) is a complex of at least 80 fungal species in 24 genera within the Dothideomycetes order Capnodiales. These epiphytes embed in the waxy epicuticle of apple fruit and colonies become visible in mid- to late summer. The blemished fruit are not marketable as fresh produce. Previous surveys of orchards in central and eastern USA and southern Europe found SBFS assemblages that were unique to geographic region. In the USA, SBFS species diversity was higher in orchards that received no fungicide sprays than those receiving fungicide sprays, suggesting that orchard management was an important determinant of SBFS species distribution and prevalence. To test the hypothesis that the composition of the SBFS complex is affected by geographic region and orchard management practices in Norway, 35 sites with a range of different management practices and cultivars were sampled. Colonies on each apple were counted according to the mycelial type, and subsamples of each mycelial type were amplified and sequenced using either primers specific to the rDNA of Capnodiales or a universal fungal primer pair for the large subunit of rDNA. Results indicated that a single genus was associated with each mycelial type. Seven genera known to cause SBFS were identified: Microcyclospora, Dissoconium, Peltaster, Microcyclosporella, Phaeothecoidiella, Schizothyrium, and Geastrumia. The percent composition of each site’s SBFS assemblage was estimated to genus. Significant differences were found in SBFS assemblages among geographic districts and management practices, and there was a significant interaction of district and management. Organic orchards tended to have the least SBFS severity and genus diversity, whereas higher SBFS diversity tended to occur in abandoned than managed orchards. This is the first survey of SBFS fungi in apple orchards in Scandinavia.

Secondary spread of Zygophiala wisconsinensis on the surface of apple fruit

Although the fungus Zygophiala wisconsinensis is a prominent component of the sooty blotch and flyspeck (SBFS) disease complex of apple, few studies have characterized in situ morphological adaptations of this or other SBFS species that accompany colonization of the epicuticular wax layer of fruit. Scanning electron microscope was used to monitor stages in the formation of sclerotium-like bodies on the wax surface, as well as ramifications from these structures to form secondary sclerotium-like bodies. At a mature stage in the formation of sclerotium-like bodies, the matrix of hyphae, conidiophores, and conidia between these bodies collapsed, resulting in formation of the independent clusters of typical colonies of species in the flyspeck mycelial type. Formation of conidiophores and secondary conidia in situ were also described for the first time for any flyspeck species. Observation of conidiophores on naturally and artificially inoculated apple peels with light microscope raises the possibility that formation of secondary conidia may be an important means of spatial dispersion of Z. wisconsinensis in apple orchards and the conidia might function in secondary spread.

Diversity of sooty blotch and flyspeck fungi from apples in northeastern Turkey

Sooty blotch and flyspeck (SBFS) is a mid- to late-season fungal disease complex that blemishes apples and other tree fruit crops in humid regions worldwide. SBFS is a concern for apple growers in northeastern Turkey, but the composition of the SBFS species assemblage in Turkey is unknown. In this study, SBFS fungi were isolated from apples collected in 2008 in the Rize Province of northeastern Turkey. Pressed SBFS colonies with subtending apple cuticle were shipped to Iowa State University for isolation. Of 633 primary isolates from 148 apple peels, 87 cultures were purified, 67 isolates were genetically characterized and 33 isolates examined for morphology. The internal transcriber spacer (ITS) ribosomal DNA and a portion of the 28S large subunit region (LSU) were compared to previously identified fungi using parsimony analysis. Putative species were delineated from ITS sequences as well as morphology on apple and in culture. Twelve species were delineated based on parsimony analysis of ITS sequences and morphology. A newly discovered and described species from the survey was Scleroramularia abundans; newly discovered putative species included Zygophiala sp. FS3.3, Stomiopeltis spp. RS7.1 and RS7.2, and Chaetothyriales sp. F1; previously recovered putative species included Zygophiala sp. FS6 and Stomiopeltis sp. RS4.1; and previously discovered and named SBFS species included Schizothyrium pomi, Zygophiala wisconsinensis, Microcyclosporella mali, Microcyclospora tardicrescens, and Peltaster fructicola. Based on parsimony analysis of the LSU, one species was placed in the subclass Chaetothyriomycetidae and 11 species were placed in subclass Dothideomycetidae. Ten species were placed in the order Capnodiales. These findings expand the documented extent of genetic diversity within the worldwide SBFS complex and are the first published description of the composition of the SBFS complex from Turkey.

Temporal Patterns in Appearance of Sooty Blotch and Flyspeck Fungi on Apples

Sooty blotch and flyspeck (SBFS) is a complex of about 80 fungal species that blemish the surface of apple fruit in humid regions worldwide. The dark colonies become visible in mid- to late summer, reducing the value of fresh fruit. Although many SBFS species can co-occur in the same orchard and even on the same apple, little is known about temporal patterns of these species, including the timing of colony appearance. To test the hypothesis that colonies of SBFS species appear on apples at characteristic times during the growing season, 50 apples were monitored weekly at three Iowa orchards in 2006 and six orchards in 2007 and 2008. However, a mean of 24.3 apples per orchard was assessed at harvest because of apple drop throughout the season. Colonies were marked with colored pens as they appeared. After harvest and after storage of apples at 2 °C for 3 months, SBFS colonies on each fruit were counted and classified by morphology, and a representative subset of colonies was excised from the fruit and preserved on dried peels for species identification using rDNA. Seventeen species were identified. Stomiopeltis spp. RS1 and RS2 appeared on apples 10 to 14 days before other SBFS taxa. Dissoconium aciculare was generally the last species to appear on apple fruit, and it continued to appear during postharvest storage. The most prevalent taxa in Iowa orchards were also the most abundant. Diversity of SBFS fungi in an orchard was positively correlated with cumulative hours of surface wetness hours due to rainfall or dew, which is believed to favor growth of SBFS fungi. Species-specific information about temporal patterns of appearance on apple fruit may lead to improved SBFS management strategies.

Diversity and Biogeography of Sooty Blotch and Flyspeck Fungi on Apple in the Eastern and Midwestern United States

Sooty blotch and flyspeck (SBFS) fungi on apple fruit were sampled from nine orchards in four midwestern U.S. states during 2000 and 30 orchards in 10 eastern U.S. states during 2005 in order to estimate taxonomic diversity and discern patterns of geographic distribution. Forty apple fruit per orchard were arbitrarily sampled and colonies of each mycelial phenotype were counted on each apple. Representative colonies were isolated, cultures were purified, and DNA was extracted. For representative isolates, the internal transcribed spacer (ITS) and large subunit (LSU) regions of ribosomal DNA were amplified and sequenced. In total, 60 SBFS putative species were identified based on ITS sequences and morphological characteristics; 30 of these were discovered in the 2005 survey. Modified Koch's postulates were fulfilled for all 60 species in an Iowa orchard; colonies resulting from inoculation of apple fruit were matched to the original isolates on the basis of mycelial type and ITS sequence. Parsimony analysis for LSU sequences from both surveys revealed that 58 putative SBFS species were members of the Dothideomycetes, 52 were members of the Capnodiales, and 36 were members of the Mycosphaerellaceae. The number of SBFS species per orchard varied from 2 to 15. Number of SBFS species and values of the Margalef and Shannon indexes were significantly (P < 0.05) lower in 21 orchards that had received conventional fungicide sprays during the fruit maturation period than in 14 unsprayed orchards. Several SBFS species, including Schizothyrium pomi, Peltaster fructicola, and Pseudocercosporella sp. RH1, were nearly ubiquitous, whereas other species, such as Stomiopeltis sp. RS5.2, Phialophora sessilis, and Geastrumia polystigmatis, were found only within restricted geographic regions. The results document that the SBFS complex is far more taxonomically diverse than previously recognized and provide strong evidence that SBFS species differ in geographic distribution. To achieve more efficient management of SBFS, it may be necessary to understand the environmental biology of key SBFS species in each geographic region.

First Report of Seven Species of Sooty Blotch and Flyspeck Fungi on Asimina triloba in Iowa.

Fungi in the sooty blotch and flyspeck (SBFS) complex cause major economic losses on cultivated pome fruits in humid regions worldwide and also colonize many species of reservoir host plants. In 2007, 10 mature fruit of pawpaw (Asimina triloba), a native tree in eastern North America exhibiting SBFS colonies on the epicuticular wax layer, were collected from wild trees in eastern Iowa. Colonies of SBFS fungi on the fruit were described according to mycelial type (1). Isolates of representative colonies on acidified water agar were subcultured on potato dextrose agar and the morphological characters were observed. After DNA was extracted from cultures and amplified by PCR using primer set ITS-1F/ITS4, 470-bp sequences were compared with those of previously identified SBFS species using NCBI BLAST. The BLAST analysis showed 100% homology of the sequences with six species that had been previously confirmed to cause SBFS on apple fruit by fulfilling Koch's postulates (1): Colletogloeum sp. FG2, Dissoconium aciculare, Peltaster sp. P2.1, P. fructicola, Stomiopeltis versicola, and Stomiopeltis sp. RS1 (GenBank Accession Nos. AY598907, AY598874, AY5988888, AY598887, AY5160165, and AY598882, respectively). Using the NCBI bl2seq application, Dothideomycete sp. CS2, an additional previously confirmed SBFS species, was revealed by sequence homology. Morphology of some SBFS species on pawpaw differed from that on apple. For example, Colletogloeum sp. FG2, which produces the fuliginous mycelial type (1) on apple fruit, developed the ridged honeycomb mycelial type on pawpaw fruit. D. aciculare and Stomiopeltis sp. RS1 produced the compact speck mycelial type on pawpaw, but are known to develop discrete speck and ramose mycelial types, respectively, on apple. These differences may result from host species differences in the epicuticular wax layer of the fruit. To our knowledge, this is the first report of SBFS fungi on A. triloba in North America, although the SBFS species Zygophiala jamaicensis was reported on the same host in Japan (2). Identifying SBFS fungi on reservoir host plants is an important step toward improving disease management strategies.