Influence of fungicides on mycotoxin production by Alternaria mali

Extracts of fungicide induced variants ofAlternaria mali were tested with mice and bacteria. Both the living fungi and their crude chloroform extracts inhibited growth ofStaphylococcus aureaus, Sarcina lutea, Bacillus mycoides, andB. subtilis. B. megaterium was not sensitive to most of the extracts and was only slightly so to the remainder. The LD₅₀ in mice when injected intraperitoneally ranged from 300 mg/kg to 2400 mg/kg; however, in some cases there were no lethal effects. The toxicity of the wild type was greatly reduced when grown in the presence of fungicide decomposition products. Altenuene, alternariol, and alternariol monomethyl ether were not found in any of the extracts.     

Climatic factors influencing spore production in Alternaria brassicae and Alternaria brassicicola

Sporulation in A. brassicae and A. brassicicola on naturally-infected leaf discs of oilseed rape and cabbage required humidities equal to or higher than 91.5% and 87% r.h. respectively. The optimum temperatures for sporulation were 18–24°C for A. brassicae and 20–30°C for A. brassicicola at which temperatures both fungi produced spores in 12–14 h. Above 24°C sporulation in A. brassicae was inhibited. At sub-optimal temperatures sporulation times for A. brassicicola were significantly longer than for A. brassicae with the differences increasing with decrease in temperature. Interrupting a 16-h wet period at 20°C with a period of 2 h at 70% or 80% r.h. did not affect sporulation in either fungus but a dry interruption of 3–4 h inhibited sporulation in both. Exposure of both fungi to alternating wet (18 h at 100% r.h., 20°C) and dry periods (6 or 30 h at 5565% r.h., 20°C) did not affect the concentration of spores produced in each wet period. Sporulation times were not affected by either the host type of the age of the host tissue. White light (136 W/m²) inhibited sporulation in A. brassicae with the degree of inhibition increasing with increasing light intensity. The effect of light on sporulation in A. brassicicola was not tested.     

Melanin production in Alternaria helianthi

Abstract

Most of the plant pathogenic fungi produce a dark phenolic polymer called melanin. The high performance liquid chromatography (HPLC) analysis of the mycelial extract of Alternaria helianthi revealed an accumulation of scytalone and a shunt metabolite 2-hydroxyjuglone which confirms the production of dihydroxynapthalene type of melanin. The growth and melanin of A. helianthi increased when grown in host extract broth at 6.5 pH and a temperature beyond 30°C had an inhibitory effect on the pathogen. The production and type of melanin produced in Alternaria helianthi is reported for the first time.     

Acquired resistance of Alternaria solani and Sclerotium rolfsii to Polyoxin-D

Acquired resistance to the antibiotic polyoxin-D was studied in two phytopathogenic fungi, Alternaria solani Sorauer, and Sclerotium rolfsii Sacc. The ED₅₀ value of the antibiotic for A. solani was 100 μg/ml and S., rolfsii 200 μg/ml. A. solani and S. rolfsii could be trained to tolerate concentrations upto 1.000 μg/ml and 2.200 μg/ml respectively. The acquired resistance in both cases was not lost on continued subculturing in fungicide-free, media. On transfer to fungicide-free media, Polyoxinresistant strains of both the fungi showed faster growth rate and appreciable reduction in sporulation compared to the original strains. The adapted strain of A. solani showed cross-resistance to Cycloheximide and Difolatan but not to Hinosan and Bayleton.     

Evaluation of Alternaria alternata ITCC4896 for use as mycoherbicide to control Parthenium hysterophorus

Mycoherbicides are specialty biotechnology products which employ the use of fungi or fungal metabolites as non-chemical alternatives, thereby reducing the input of harmful chemicals to control noxious weeds. The present communication emphasises the potential of an indigenous isolate of Alternaria alternata ITCC 4896 as a mycoherbicide for the global weed Parthenium hysterophorus. Of the various spore concentrations tested by in vitro detached leaf bioassay, 1 × 10⁶ spores/ml was the most effective, inducing 89.2% leaf area damage on the seventh day and was further tested by the whole plant bioassay. Both in vitro detached leaf assay and whole plant bioassay exhibited a similar trend in disease development, exhibiting 50% damage at 96 hours post-treatment. However, 100% mortality was observed in the whole plant bioassay on the seventh day. This is the very first report on the bioweedicidal potential of Alternaria alternata ITCC 4896 (LC#508) for use as a mycoherbicide for Parthenium hysterophorus.     

Aflatoxins in sunflower seeds: Influence of Alternaria alternata on aflatoxin production by Aspergillus parasiticus

The aim of the present work was to determine the influence of Alternaria alternata upon aflatoxin production by Aspergillus parasiticus.A mixture of spores of both strains was inoculated in sunflower seeds at 0,90 a_w, and incubated for 42 days at 28 °C ±1.The cultures were observed and analyzed every 7 days to determine the infection level of the seeds and the production of aflatoxins. Results showed that when the seeds were inoculated only with Aspergillus parasiticus, 100% were infected from the 7th day.When Aspergillus parasiticus and Alternaria alternata were simultaneously inoculated the infection level of the seeds was 100% for Aspergillus parasiticus following 7 days of inoculation and 0% for Alternaria alternata. After the 14th day of inoculation there was no significant difference in the infection percentage of both strains (approximately 80% of each one). As far as toxin production is concerned a remarkable decrease was observed when seeds were inoculated with both strains simultaneously.In accordance to the results, Alternaria alternata would not compete with Aspergillus parasiticus in colonization of seeds but would either degrade the aflatoxins by Aspergillus parasiticus or compete for aflatoxin biosynthesis precursors. Alternaria alternata could also secrete some substance that specifically inhibits aflatoxin synthesis.     

Occurrence and moisture requirements of microbial growth in building materials

Microbial growth was studied in six damp buildings. Mesophilic fungi, especially Penicillium spp., yeasts, and species of Cladosporium and Aspergillus, occurred most abundantly on building constructions. Thermophilic fungi and mesophilic actinomycetes were occasionally found. A toxigenic fungus, Stachybotrys sp., was also detected on cellulose-based materials. In a cytotoxicity test, 23% of samples were positive. Spore counts varied considerably on materials, but no correlation between counts and the substrate or its water activity (a_w) was observed. In experiments a rapid increase in CO₂ production and spore propagule count was observed in all materials incubated at a relative humidity (RH) (RH=0·01^*water activity) of 96–98°. Some differences were noted between materials in CO₂ evolved, but not in propagule counts.     

Influence of Phospholipids on Growth, Sporulation and Virulence of the Endoparasitic Fungi Drechmeria coniospora, Verticillium balanoides and Harposporium anguillulae in Liquid Culture

Verticillium balanoides mycelial growth was stimulated on solid corn meal agar (1.7 %) and in liquid corn meal broth (0.2 %) upon the addition of phospholipids at various concentrations. Sporulation differed with phospholipid products and was highest in pure corn meal. Drechmeria coniospora mycelial growth increased upon addition of phospholipids at all concentrations in solid or liquid culture. Sporulation increased at high concentration (1000 ppm) and decreased at low concentration (100 ppm) of phospholipids in the medium. For both fungi, infectivity of conidia produced in liquid culture decreased when compared to conidia from parasitized nematodes. Addition of phospholipids partly restored this effect. Harposporium anguillulae mycelial growth and sporulation was not affected by addition of phospholipids to solid or liquid corn meal medium.     

Species of plants and associated arbuscular mycorrhizal fungi mediate mycorrhizal responses to CO2 enrichment

It has been suggested that enrichment of atmospheric CO₂ should alter mycorrhizal function by simultaneously increasing nutrient‐uptake benefits and decreasing net C costs for host plants. However, this hypothesis has not been sufficiently tested. We conducted three experiments to examine the impacts of CO₂ enrichment on the function of different combinations of plants and arbuscular mycorrhizal (AM) fungi grown under high and low soil nutrient availability. Across the three experiments, AM function was measured in 14 plant species, including forbs, C₃ and C₄ grasses, and plant species that are typically nonmycorrhizal. Five different AM fungal communities were used for inoculum, including mixtures of Glomus spp. and mixtures of Gigasporaceae (i.e. Gigaspora and Scutellospora spp.). Our results do not support the hypothesis that CO₂ enrichment should consistently increase plant growth benefits from AM fungi, but rather, we found CO₂ enrichment frequently reduced AM benefits. Furthermore, we did not find consistent evidence that enrichment of soil nutrients increases plant growth responses to CO₂ enrichment and decreases plant growth responses to AM fungi. Our results show that the strength of AM mutualisms vary significantly among fungal and plant taxa, and that CO₂ levels further mediate AM function. In general, when CO₂ enrichment interacted with AM fungal taxa to affect host plant dry weight, it increased the beneficial effects of Gigasporaceae and reduced the benefits of Glomus spp. Future studies are necessary to assess the importance of temperature, irradiance, and ambient soil fertility in this response. We conclude that the affects of CO₂ enrichment on AM function varies with plant and fungal taxa, and when making predictions about mycorrhizal function, it is unwise to generalize findings based on a narrow range of plant hosts, AM fungi, and environmental conditions.     

Screening of white-rot fungi for their ability to mineralize polycyclic aromatic hydrocarbons in soil

Soil samples from an agricultural field contaminated with 10 ppm¹⁴C-benz(a)anthracene in glass tubes were brought into contact with cultures of wood-rotting fungi, precultivated on wheat straw substrate. Forty-five strains of white-rot fungi and four brown-rot fungi were tested for their ability to colonize the soil and to mineralize¹⁴C-benz(a)anthracene to¹⁴CO₂ within a 20-week incubation time. Twenty-two white-rot fungi and all brown-rot fungi were unable to colonize the soil. Twenty-three strains of white-rot fungi, all belonging to the genusPleurotus, colonized the soil. During the experiment the noncolonizing fungi and their substrate disintegrated more and more to a nonstructured pulp from which water diffused into the soil. The same phenomenon was observed in the control which contained only straw without fungus and contaminated soil. In samples with colonizing fungi the substrate as well as the mycelia in the soil remained visibly unchanged during the entire experiment. Surprisingly, most samples with fungi not colonizing the soil and the control without fungus liberated between 40 and 58 % of the applied radioactivity as¹⁴CO₂ whereas the samples with the colonizing fungi respired only 15–25 % as¹⁴CO₂. This was 3–5 times more¹⁴CO₂ than that liberated from the control (4.9 %) which contained only contaminated soil without straw and fungus. A similar result was obtained with selected colonizing and noncolonizing fungi and soil contaminated with 10 ppm¹⁴C-pyrene. However, in pure culture studies in which¹⁴C-pyrene was added to the straw substrate,Pleurotus sp. (P2), as a representative of the colonizing fungi, mineralized 40.3 % of the added radioactivity to¹⁴CO₂. The noncolonizing fungiDichomitus squalens andFlammulina velutipes liberated only 17.2 or 1.7 %, respectively, as¹⁴CO₂. These results lead to the hypothesis that the native soil microflora stimulated by the formed products of straw lysis is responsible for high degradation rates found with noncolonizing fungi.     

The potential effect of high atmospheric CO2 on soil fungi–invertebrate interactions

Litter mixtures of four meadow plant species, Cardamine hirsuta, Poa annua, Senecio vulgaris, and Spergula arvensis, were produced from laboratory model terrestrial ecosystems maintained at either ambient or enriched (ambient + 200 µmol mol^?1) CO₂ concentrations. The effect of litter source on the oviposition attractivity of fungi to the sciarid fly Lycoriella ingenua was tested for seven fungal species (Absidia glauca, Cladosporium cladosporioides, C. herbarum, Fusarium oxysporum, Penicillium arenicola, P. chrysogenum, and P. janthinellum). For all species, except F. oxysporum, oviposition attractivity increased when the fungi were growing on litter derived from CO₂‐enriched environments. The relative increase of the oviposition attractiveness of fungi growing on CO₂‐enriched litter differed substantially and resulted in a shift in sciarid fly oviposition preference. For example, when P. chrysogenum and C. herbarum grew on ambient litter, P. chrysogenum was more attractive; the opposite was true for mycelia growing on enriched litter. The effect of litter source on the suitability of four fungal species for larval development was also tested. In two species of fungi (A. glauca and C. herbarum) suitability was significantly higher if growing on CO₂‐enriched litter. With P. chrysogenum the opposite was true. The consequences of these rarely considered CO₂‐induced trophic interactions on ecosystem processes such as nutrient feedback cycles between plants and soil decomposition are considered.     

Taxonomic Characterization and Experimental Host Ranges of Four Newly Recorded Species of Alternaria from Japan

Alternaria fungi are important plant pathogens. Here, we identified three species new to the Japanese mycoflora: Alternaria celosiae, Alternaria crassa and Alternaria petroselini. We proposed a new name for A. celosiae (E.G. Simmons & Holcomb) Lawrence, Park & Pryor, a later homonym of A. celosiae (Tassi) O. S?vul. To characterize these and a fourth morphological taxon, Alternaria alstroemeriae, which was recently added to Japan's mycoflora, an integrated species concept was tested. We determined the host range of each isolate using inoculation tests and analysed its phylogenetic position using sequences of the internal transcribed spacer rDNA. The pathogenicity of our A. alstroemeriae isolate was strictly limited to Alstroemeria sp. (Alstroemeriaceae), but the species was phylogenetically indistinguishable from other small‐spored Alternaria. Alternaria celosiae on Celosia argentea var. plumosa (Amaranthaceae) was also pathogenic to Amaranthus tricolor, to Alternanthera paronychioides and weakly to Gomphrena globosa (all Amaranthaceae) and formed a clade with the former Nimbya celosiae. Alternaria crassa on Datura stramonium (Solanaceae) was also pathogenic to Brugmansia × candida and Capsicum annuum in Solanaceae, but not to other confamilial plants; phylogenetically it belonged to a clade of large‐spored species with filamentous beaks. Morphological similarity, phylogenetic relationship and experimental host range suggested that A. crassa, Alternaria capsici and Alternaria daturicola were conspecific. Alternaria petroselini on Petroselinum crispum (Apiaceae) was pathogenic to five species in the tribe Apieae as well as representatives of Bupleureae, Coriandreae, Seliaeae and Scandiceae in Apiaceae. Both phylogeny and morphology suggested conspecificity between A. petroselini and Alternaria selini.     

Pathogenicity of Alternaria alternata and Fusarium moniliforme and Phytotoxicity of AAL-toxin and Fumonisin B1 on Tomato Cultivars

Phytotoxicity of AAL-toxin and fumonisin B₁ to six cultivars of tomato was compared with the pathogenicity of their fungal sources, Alternaria alternata and Fusarium moniliforme, respectively. These include two AAL-toxin susceptible cultivars with genotypes(asc/asc), three resistant cultivars (Asc/Asc), and a heterozygous cultivar (Asc/asc.) A. alternata spores were pathogenic to the susceptible but not to the resistant cultivars F. moniliforme was not pathogenic to any of the tomatoes. Filtrates of both fungi grown on rice containing their respective toxins caused necrosis within 48 h and eventually mortality on susceptible cultivars but not on the resistant lines. The heterozygous cultivar Asc/asc showed minimal damage and no mortality after 14 days exposure to both filtrates and both toxins. The spores of both fungi had no effect on heterozygous intact plants. Tomato leaf disc bioassays with AAL-toxin and fumonisin B₁ at 1μM caused cellular leakage and reduced chlorophyll content in susceptible cultivars and minimal effects on the heterozygous and resistant varieties.     

Changes in the microbial community structure of bacteria,archaea and fungi in response to elevated CO2 and warming in an Australian native grassland soil

The microbial community structure of bacteria, archaea and fungi is described in an Australian native grassland soil after more than 5 years exposure to different atmospheric CO₂ concentrations ([CO₂]) (ambient, + 550 ppm) and temperatures (ambient, + 2°C) under different plant functional types (C ₃ and C ₄ grasses) and at two soil depths (0–5 cm and 5–10 cm). Archaeal community diversity was influenced by elevated [CO₂], while under warming archaeal 16S rRNA gene copy numbers increased for C ₄ plant Themeda triandra and decreased for the C ₃ plant community (P < 0.05). Fungal community diversity resulted in three groups based upon elevated [CO₂], elevated [CO₂] plus warming and ambient [CO₂]. Overall bacterial community diversity was influenced primarily by depth. Specific bacterial taxa changed in richness and relative abundance in response to climate change factors when assessed by a high‐resolution 16S rRNA microarray (PhyloChip). Operational taxonomic unit signal intensities increased under elevated [CO₂] for both Firmicutes and Bacteroidetes, and increased under warming for Actinobacteria and Alphaproteobacteria. For the interaction of elevated [CO₂] and warming there were 103 significant operational taxonomic units (P < 0.01) representing 15 phyla and 30 classes. The majority of these operational taxonomic units increased in abundance for elevated [CO₂] plus warming plots, while abundance declined in warmed or elevated [CO₂] plots. Bacterial abundance (16S rRNA gene copy number) was significantly different for the interaction of elevated [CO₂] and depth (P < 0.05) with decreased abundance under elevated [CO₂] at 5–10 cm, and for Firmicutes under elevated [CO₂] (P < 0.05). Bacteria, archaea and fungi in soil responded differently to elevated [CO₂], warming and their interaction. Taxa identified as significantly climate‐responsive could show differing trends in the direction of response (‘+’ or ‘?’) under elevated CO₂ or warming, which could then not be used to predict their interactive effects supporting the need to investigate interactive effects for climate change. The approach of focusing on specific taxonomic groups provides greater potential for understanding complex microbial community changes in ecosystems under climate change.     

Responses of fungal root colonization,plant cover and leaf nutrients to long‐term exposure to elevated atmospheric CO2 and warming in a subarctic birch forest understory

Responses of the mycorrhizal fungal community in terrestrial ecosystems to global change factors are not well understood. However, virtually all land plants form symbiotic associations with mycorrhizal fungi, with approximately 20% of the plants' net primary production transported down to the fungal symbionts. In this study, we investigated how ericoid mycorrhiza (ErM), fine endophytes (FE) and dark septate endophytes (DSE) in roots responded to elevated atmospheric CO₂ concentrations and warming in the dwarf shrub understory of a birch forest in the subarctic region of northern Sweden. To place the belowground results into an ecosystem context we also investigated how plant cover and nutrient concentrations in leaves responded to elevated atmospheric CO₂ concentrations and warming. The ErM colonization in ericaceous dwarf shrubs increased under elevated atmospheric CO₂ concentrations, but did not respond to warming following 6 years of treatment. This suggests that the higher ErM colonization under elevated CO₂ might be due to increased transport of carbon belowground to acquire limiting resources such as N, which was diluted in leaves of ericaceous plants under enhanced CO₂. The elevated CO₂ did not affect total plant cover but the plant cover was increased under warming, which might be due to increased N availability in soil. FE colonization in grass roots decreased under enhanced CO₂ and under warming, which might be due to increased root growth, to which the FE fungi could not keep up, resulting in proportionally lower colonization. However, no responses in aboveground cover of Deschampsia flexuosa were seen. DSE hyphal colonization in grass roots significantly increased under warmer conditions, but did not respond to elevated CO₂. This complex set of responses by mycorrhizal and other root‐associated fungi to global change factors of all the fungal types studied could have broad implications for plant community structure and biogeochemistry of subarctic ecosystems.     

Does carbon partitioning in ectomycorrhizal pine seedlings under elevated CO2 vary with fungal species?

Enhanced soil respiration in response to elevated atmospheric CO₂ has been demonstrated, and ectomycorrhizal (ECM) fungi are of particular interest since they partition host-derived photoassimilates belowground. Although a strong response of ECM fungi to elevated CO₂ has been shown, little is still known about the functional diversity among species. We studied carbon (C) partitioning in mycorrhizal Scots pine seedlings in response to short-term CO₂ enrichment, using seven ECM species with different ecological strategies. Mycorrhizal associations were synthesised and seedlings grown in large Petri dishes containing peat:vermiculite and nutrient solution for 10–15 weeks, after which half of the microcosms were exposed to elevated CO₂ treatment (710 ppm) for 15 days and the other half were kept in ambient CO₂ treatment. Partitioning of C was quantified by pulse labelling the seedlings with ¹⁴CO₂ and examining the distribution of labelled assimilates in shoot, root and extraradical mycelial compartments by destructive harvest and liquid scintillation counting. Fungal biomass was determined with PLFA analysis. The respiratory loss of ¹⁴CO₂ was on average greater in the elevated CO₂ treatment for most species compared to the ambient CO₂ treatment. More label was retrieved in the shoots in the ambient CO₂ treatment compared to elevated CO₂ (significant for P. involutus and P. fallax). Greater amounts of label were found in the extraradical mycelial compartment in all species (except P. involutus) in elevated CO₂ compared to ambient CO₂ (significant for L. bicolor, P. byssinum, P. fallax and R. roseolus). Fungal biomass production increased significantly with elevated CO₂ for two species (H. velutipes and A. muscaria); three species (P. fallax, P. involutus and R. roseolus) showed a similar but non-significant trend, whereas L. bicolor and P. byssinum produced less biomass in elevated CO₂ compared to ambient CO₂. When ¹⁴C in the mycelial compartment and respiration was expressed per unit fungal PLFA the difference between CO₂ treatments disappeared. We demonstrated that different ECM fungal isolates respond differently in C partitioning in response to CO₂ enrichment. These results suggest that under certain growth conditions, when nutrients are not limiting, ECM fungi respond rapidly to increasing C-availability through changed biomass production and respiration.     

Plant species-specific changes in root-inhabiting fungi in a California annual grassland: responses to elevated CO2 and nutrients

Five co-occurring plant species from an annual mediterranean grassland were grown in monoculture for 4 months in pots inside open-top chambers at the Jasper Ridge Biological Preserve (San Mateo County, California). The plants were exposed to elevated atmospheric CO₂ and soil nutrient enrichment in a complete factorial experiment. The response of root-inhabiting non-mycorrhizal and arbuscular mycorrhizal fungi to the altered resource base depended strongly on the plant species. Elevated CO₂ and fertilization altered the ratio of non-mycorrhizal to mycorrhizal fungal colonization for some plant species, but not for others. Percent root infection by non-mycorrhizal fungi increased by over 500% for Linanthus parviflorus in elevated CO₂, but decreased by over 80% for Bromus hordeaceus. By contrast, the mean percent infection by mycorrhizal fungi increased in response to elevated CO₂ for all species, but significantly only for Avena barbata and B. hordeaceus. Percent infection by mycorrhizal fungi increased, decreased, or remained unchanged for different plant hosts in response to fertilization. There was evidence of a strong interaction between the two treatments for some plant species and non-mycorrhizal and mycorrhizal fungi. This study demonstrated plant species- and soil fertility-dependent shifts in below-ground plant resource allocation to different morpho-groups of fungal symbionts. This may have consequences for plant community responses to elevated CO₂ in this California grassland ecosystem. Received: 2 June 1997 / Accepted: 22 August 1997     

Alternaria on cruciferous plants. 4.Alternaria species on seed of some cruciferous crops and their pathogenicity

The incidence ofAlternaria spp. on seed samples of cruciferous vegetable crops was surveyed between 1990 and 1992. Some commercial seed lots of crucifers which are commonly grown in Japan were infested withAlternaria species. ThreeAlternaria species were encountered on the seed samples ofBrassica campestris, B. orelacea, andRaphanus sativus. The most frequently detected species wereA. japonica andA. alternata onB. campestris, A. brassicicola onB. oleracea, andA. japonica andA. alternata onR. sativus, respectively.Alternaria brassicae was not detected in this study.Alternaria brassicicola isolates from these crops produced necrotic lesions on all of the crucifer seedlings inoculated, whileA. japonica induced different reactions in different plants or plant parts depending on isolates used in inoculation tests. In contrast, most isolates ofA. alternata could not produce necrotic lesions on foliage leaves of crucifers inoculated, although some of them produced clear lesions only on cotyledons.Alternaria alternata associated with these cruciferous crop seeds was considered to be an oppotunistic parasite of these crops.     

Growth inhibition effect of pyroligneous acid on pathogenic fungus,<Emphasis Type="Italic">Alternaria mali</Emphasis>, the agent of Alternaria blotch of apple

We investigated the growth inhibition effect of pyroligneous acid on the pathogenic fungus,Alternaria mali, which is known to be the agent of Alternaria blotch of apple plants. Chemical control ofA. mali could be achieved through the use of agrochemical fungicides, while the substitute for agrochemical control is gradually increasing. It was observed that pyroligneous acid exhibited antifungal activity against some plant pathogenic fungi. More specifically, the growth ofA. mali was completely inhibited in pyroligneous acid at a dilution of 1∶32. When its antifungal activity was compared to that of polyoxin B, which is used for the chemical control of Alternaria blotch of apple, it was observed that the antifungal activity of pyroligneous acid diluted at 1∶32 corresponded to 2.0 mg/mL of polyoxin B. Consequently, it is concluded that the diluted pyroligneous acid can substitute for polyoxin B, thereby reducing the use of the agrochemical for the control of Alternaria blotch of apple.