Culturable Fungi of Stored ‘Golden Delicious’ Apple Fruits: A One-Season Comparison Study of Organic and Integrated Production Systems in Switzerland

The effects of organic and integrated production systems on the culturable fungal microflora of stored apple fruits from five matched pairs of certified organic and integrated ‘Golden Delicious’ farms were studied at five representative production sites in Switzerland. Isolated fungi were identified morphologically. Colonization frequency (percentage of apples colonized), abundance (colony numbers), and diversity (taxon richness) were assessed for each orchard. The standard quality of the stored fruits was comparable for both organic and integrated apples and complied with national food hygiene standards. Yeasts (six taxa) and the yeast-like fungus Aureobasidium pullulans were the dominant epiphytes, filamentous fungi (21 taxa) the dominant endophytes. The most common fungi occurred at all sites and belonged to the “white” and “pink” yeasts, yeast-like A. pullulans, filamentous fungi Cladosporium spp., Alternaria spp., and sterile filamentous fungi. Canonical correspondence analysis of the total fungal community revealed a clear differentiation among production systems and sites. Compared to integrated apples, organic apples had significantly higher frequencies of filamentous fungi, abundance of total fungi, and taxon diversity. The effects of the production system on the fungal microflora are most likely due to the different plant protection strategies. The incidence of potential mycotoxin producers such as Penicillium and Alternaria species was not different between production systems. We suggest that higher fungal diversity may generally be associated with organic production and may increase the level of beneficial and antagonistically acting species known for their potential to suppress apple pathogens, which may be an advantage to organic apples, e.g., in respect to natural disease control.     

The microflora of ripening barley grain and the effects of pre harvest fungicide application

Newly-emerged ears of barley soon became colonised by micro-organisms with numbers increasing to 5·8 × 10⁵ viable propagules/g dry weight by harvest. Bacteria were numerically predominant throughout. Yeasts and yeast-like fungi were also numerous during the early stages of grain development but were exceeded by propagules of filamentous fungi during ripening, with Cladosporium spp., Alternaria alternata, Epicoccum purpurascens and Verticillium lecanii most abundant. Numbers of most micro-organisms were greatest in a wet season but Alternaria was equally abundant in hot dry weather. Application of fungicides at or after anthesis modified the grain microflora. Captafol was most effective overall in decreasing numbers of fungi. However, benomyl decreased Cladosporium inoculum more than catpafol but was ineffective against Alternaria which became more numerous on benomyl-treated grain than on untreated. Yield increases of up to 4% were obtained by late fungicide treatment, least in a hot, dry year. Germination was also increased by some treatments by up to 5%.     

Effect of increased CO2 concentration and temperature on the phyllosphere mycoflora of winter wheat flag leaves during ripening

The impact of elevated carbon dioxide (CO₂, 600/700 μmol mol^-1) and temperature (+ 4°C) on phyllosphere fungi colonising flag leaves of mini crops of winter wheat cv. Mercia between anthesis and harvest was determined in a computer-controlled environment facility in 1993 and 1994. In both years the total fungal populations (cm² leaf) were found to have increased due to exposure to either elevated CO₂ and elevated CO₂+ temperature treatments. This was mainly due to significant increases in populations of Cladosporium spp. (C. cladosporioides and C. herbarum) on the flag leaves during ripening. Other phyllosphere component species such as white and pink yeasts were not markedly affected by treatments. The range of fungal species found in such controlled environment chambers was narrower than that commonly found on flag leaves of field grown crops. Common and important colonisers of leaves and ripening ears such as Aureobasidium pullulans, Epicoccum nigrum and Fusarium spp. were seldom isolated.     

The phylloplane microflora of ripening wheat and effect of late fungicide applications

Flag leaves and ears of spring wheat cv. Timmo (in 1980) and winter wheat cv. Maris Huntsman in 1981 and 1982 were colonised by a variety of micro-organisms whose numbers increased rapidly between anthesis and harvest. The predominant mycoflora were yeasts, yeast-like fungi and filamentous fungi which included Cladosporium spp., Verticillium lecanii, Alternaria alternata, Fusarium spp. and Epicoccum nigrum. Although similar species were isolated, their relative abundance on flag leaves and ears differed. The fungicide captafol was most effective as a protectant and significantly decreased populations of fungi on flag leaves and ears for 6 and 4 wk respectively, compared to untreated controls. Benomyl and Delsene M (carbendazim + maneb) were the most effective of the systemic sprays and formulations. In general, fungicides affected populations of yeasts, yeast-like fungi and Cladosporium spp. most while Alternaria was tolerant of all treatments. Yields of winter wheat were increased in two seasons by an average 0–2 t ha^-1 (2–4%) following a single late fungicide treatment at G.S. 50 or 60 and 0–41 t ha^-1 (5-1%) when this was combined with an early spray against foliar diseases (G.S. 38–40). Individual treatments increased yield by up to 12% with little difference between applications at G.S. 50 or 60. The yield benefit came mainly from increased 1000-grain weights. Germination of the treated grain was increased only slightly.     

Side effects of propiconazole (tilt 250 ECTM) on non-target soil fungi in a field trial compared with natural stress effects

The present study was performed as a dose-response field experiment using a trade marked formulation of the ergosterol biosynthesis inhibiting fungicide, propiconazole, applied at the recommended and ten times the recommended application rates. The soil dilution plate method was used to isolate fungi from 0–1 and 1–2 cm soil depth. Soil samples were taken 10 times during the period from May 22 to August 11, 1986. The numbers of yeasts and filamentous fungi were enumerated, the latter includingCladosporium andPenicillium, which were also enumerated separately. The fluctuations in fungal occurrence due to the propiconazole treatment were smaller than seasonal fluctuations, these most likely being caused by variations in the soil matric potential and by soil invasion of phyllosphere fungi. Fungicide treatment had significant inhibitory effects on the filamentous fungi, especially on theCladosporium, whereas no significant effects were found on the yeasts and onPenicillium spp. From an ecotoxicological point of view, it is important that the effects were considerably delayed, with respect to the time of fungicide application.     

Survey of bovine mycotic mastitis in dairy herds in the State of São Paulo,Brazil

The purpose of this study was to isolate fungi from the quarter milk of cow udders from several dairy herds and to identify the different genera and species involved in mastitis. A total of 2078 milk samples from normal, clinical and subclinical mastitis quarters from 22 dairy herds of 16 districts in the State of São Paulo, Brazil was utilized in this survey. Two hundred and fifty one (12.07%) fungi were isolated from the samples. Two hundred and eight of these (82.86%) were yeasts and 30 (11.95%) were moulds. The fungi were isolated in pure culture (24.77%) or in cultures mixed with bacteria (72.22%). The yeasts isolated were:Cryptococcus spp. (71 strains),Rhodotorula spp. (40),Candida spp. (68),Trichosporon cutaneum (21),Aureobasidium pullulans (7), andPichia ohmeri (1). Moulds classified in following genera were also isolated:Aspergillus (3),Penicillium (3),Alternaria (3),Phoma (3),Epicoccum (2), andGeotrichum (16).     

Incidence, Aggressiveness and In Planta Interactions of Botrytis cinerea and other Filamentous Fungi Quiescent in Grape Berries and Dormant Buds in Central Washington State

Recovery of quiescent filamentous fungi from non‐symptomatic grape berries and dormant buds demonstrated dominance of Alternaria, Aureobasidium, Cladosporium, Ulocladium and other dematiaceous hyphomycetes. Up to 78% of berries contained fungi prior to harvest. Botrytis cinerea was recovered from 0.2 to 0.5% of surface‐disinfested berries just subsequent to fruit set, and 1.6–4.8% of surface‐disinfested, over‐wintered dormant buds. In laboratory inoculations of mature grape berries with strains of Alternaria, Aureobasidium, Cladosporium, Ulocladium and Botrytis, only the latter was aggressive in rotting berry fruits. Inoculations with B. cinerea alone and in combination with strains of Alternaria, Aureobasidium, Cladosporium and Ulocladium recovered from grape demonstrated that prior occupation of wound sites by the latter fungi resulted in reduced lesion size compared to inoculation with B. cinerea alone.     

Contribution of leaf surface fungi to the air spora

High concentrations of airborne fungal spores frequently occur from spring through fall in temperate areas of the world. Although it is generally assumed that fungi on leaf surfaces are contributors to the air spora, little data are available comparing the types of fungi found on leaf surfaces with those in the atmosphere. Air sampling was carried out with a Burkard Spore Trap located on the roof of a building on the University of Tulsa campus using standard methods. Leaf samples were aseptically collected from Ulmus americana and Quercus palustris trees on campus, placed in sterile plastic bags, and brought to the lab. For each leaf, 4 cm² areas of both upper and lower leaf surfaces were swabbed and plated on malt extract agar with streptomycin. Cultures were incubated at room temperature for 5–7 days and then examined microscopically. Results were expressed as colony forming units (CFU)/cm². Twenty-one fungal taxa were identified from the air samples. The most abundant taxa were Cladosporium, ascospores, basidiospores, and Alternaria; together these four spore types comprised over 90% of the yearly total. Yeasts were the most abundant fungi isolated from both leaf types. Among the mycelial fungi were Phoma species, followed by Cladosporium and Alternaria. Overall twenty genera of filamentous fungi were identified. Yeasts and Phoma are normally splash dispersed and were not identified in the Burkard air samples. However, 10 taxa isolated from leaf surfaces were registered in air samples. Crude estimates of the leaf surface area of each tree suggest that the total fungal load was approximately 5.04×10⁸ CFU for Ulmus and 2.71×10⁸ CFU for Quercus. Of these levels, 19% were from fungi also detected in air samples. The data suggest that some leaf-surface fungi are major contributors to the air spora.     

Pheromone-mediated mass trapping and population diversion as strategies for suppressing Carpophilus spp. (Coleoptera: Nitidulidae) in Australian stone fruit orchards

1 Five experiments were conducted during 1995–99 in stone fruit orchards on the Central Coast and in inland New South Wales, Australia, on the use of synthetic aggregation pheromones and a coattractant to suppress populations of the ripening fruit pests Carpophilus spp. (Coleoptera: Nitidulidae). 2 Perimeter‐based suppression traps baited with pheromone and coattractant placed at 3 m intervals around small fruit blocks, caught large numbers of Carpophilus spp. Very small populations of Carpophilus spp. occurred within blocks, and fruit damage was minimal. 3 Carpophilus spp. populations in stone fruit blocks 15–370 m from suppression traps were also small and non‐damaging, indicating a large zone of pheromone attractivity. 4 Pheromone/coattractant‐baited suppression traps appeared to divert Carpophilus spp. from nearby (130 m) ripening stone fruit. Ten metal drums containing decomposing fruit, baited with pheromone and treated with insecticide, attracted Carpophilus spp. and appeared to reduce populations and damage to ripening fruit at distances of 200–500 m. Populations and damage were significantly greater within 200 m of the drums and may have been caused by ineffective poisoning or poor quality/overcrowding of fruit resources in the drums. 5 Suppression of Carpophilus spp. populations using synthetic aggregation pheromones and a coattractant appears to be a realistic management option in stone fruit orchards. Pheromone‐mediated diversion of beetle populations from ripening fruit may be more practical than perimeter trapping, but more research is needed on the effective range of Carpophilus pheromones and the relative merits of trapping compared to attraction to insecticide‐treated areas.     

Quantitative and qualitative seasonal changes in the microbial community from the phyllosphere of sugar beet (Beta vulgaris)

Bacteria, yeasts and filamentous fungi colonizing immature, mature and senescing primary leaves of field grown Beta vulgaris (sugar beet) were analysed over a complete growing season. Greatest microbial numbers were detected on senescing primary leaves and these numbers increased over most of the season. The number of colonizers detected on mature leaves was found to be stable over most of the study.Filamentous fungi and yeasts were identified to the genus level and the communities found to have greatest diversity during the summer months. There was no consistent pattern of diversity according to leaf type. Two genera of filamentous fungi, Cladosporium and Alternaria and two yeast genera, Cryptococcus and Sporobolomyces were the most numerous fungal populations isolated. Only 8 filamentous fungi and 3 yeast genera were commonly isolated on PDA (potato dextrose agar).Bacterial strains (1236) were isolated on Tryptic Soy Broth (TSB) agar and identified to species, or in some cases sub-species level, by analysis of their fatty acid methyl ester (FAME) profiles. Isolated bacteria were grouped into 78 named and 37 unnamed species clusters. Greatest number of bacterial species were isolated from young plants and leaves, sampled during the autumn months. Bacterial community diversity was lowest in mid-summer and winter months. Pseudomonas was the most commonly isolated genus and Erwinia herbicola the most common species. P. aureofaciens was the only species isolated from soil that was also isolated from the phyllosphere of B. vulgaris throughout the season.     

Daily and seasonal variations ofAlternaria andCladosporium airborne spores in León (North-West, Spain)

The spores ofAlternaria andCladosporium are present throughout the year in the atmosphere of León (NW Spain), although they show an important seasonal variation. To understand the relationship between the number of spores and climatic factors,Alternaria andCladosporium spores counts for January 1994 to December 1995 were examined by means of correlation analyses. The results of weekly samples of both years showed that the spores concentration of two taxa are significantly and positively correlated with maximum and minimum temperature and sunshine hours and negatively with relative humidity. The statistical analysis of daily samples generally showed the same results. In the hourly distribution of spore concentrations we can see a similar behaviour ofAlternaria andCladosporium, with most spores collected in the 12–14 h period.     

Differences in the microflora of scarified and unscarified seeds ofKarwinskia humboldtiana (Rhamnaceae)

Seeds ofKarwinskia humboldtiana obtained from a 1997 collection in the locality of Villa de García Nuevo (León, Mexico) were contaminated with spores of filamentous fungi, bacteria and yeasts. The concentration of microorganisms in unscarified seeds ranged from 3.0×10³ to 7.5×10³ CFU/g. Predominant were bacterial isolates of the generaAeromonas sp.,Bacillus, andPseudomonas; from filamentous fungi were identifiedAlternaria, Aspergillus niger, Cladosporium sp.,Fusarium sp.,Mucor sp.,Penicillium commune, Trichothecium sp.; from yeastsRhodotorula sp. andSaccharomyces cerevisiae. Seed scarification significantly reduced the microbial contamination. Of the original fungal isolates, only two were identified on scarified seeds,viz. Cladosporium sp. andSaccharomyces cerevisiae; although a relatively high incidence of a unidentifiable ofPenicillium sp. was found, the bacterial spectrum was not altered. Treatment of scarified seeds with Vitavax 200 WP and Pomarsol Forte 80 WP (3 mg/g seeds) augmented germination by 10–19% compared to treated unscarified seeds, and by 16–31% compared to untreated unscarified seeds.     

The effect of meteorological factors on the daily variation of airborne fungal spores in Granada (southern Spain)

A study was made of the link between climatic factors and the daily content of certain fungal spores in the atmosphere of the city of Granada in 1994. Sampling was carried out with a Burkard 7-day-recording spore trap. The spores analysed corresponded to the taxa Alternaria, Ustilago and Cladosporium, with two morphologically different spore types in the latter genus, cladosporioides and herbarum. These spores were selected both for their allergenic capacity and for the high level of their presence in the atmosphere, particularly during the spring and autumn. The spores of Cladosporium were the most abundant (93.82% of the total spores identified). The Spearman correlation coefficients between the spore concentrations studied and the meteorological parameters show different indices depending on the taxon being analysed. Alternaria and Cladosporium are significantly correlated with temperature and hours of sunlight, while Ustilago shows positive correlation indices with relative humidity and negative indices with wind speed. Received: 16 April 1998 / Revised: 27 September 1999 / Accepted: 27 October 1999     

Searching for eukaryotic life preserved in Antarctic permafrost

Fungi and yeasts isolated in pure culture from Antarctic permafrost collected at different depths in the McMurdo Dry Valleys were identified with cultural, physiological and molecular methods. Fungi belonged to the genera Penicillium, Eurotium, Cladosporium, Alternaria, Engyodonthium, Aureobasidium, Cordyceps, Rhizopus and yeasts to the genera Cryptococcus and Sporidiobolus. All the strains can be defined as mesophilic psychrotolerant. The molecular analyses revealed that these fungal genotypes do not deviate from the global gene pool of fungi commonly spreading worldwide at present, but possible ancestral strains have been found on the base of metabolic profiles.     

Assessment of Abundance and Species Composition of Filamentous Fungi in the Underground Rzeczka Complex in Sowie Mountains (Lower Silesia,Poland)

Our study is the first mycological evaluation of the air and the rocks in the underground Rzeczka complex in Sowie Mountains (Lower Silesia, Poland). The density of filamentous fungi isolated from the air inside and outside the adit ranged between 245.5 to 1332.6 Colony Forming Units in 1 m³ of air. Sixteen species of filamentous fungi were isolated from the internal air sampled and 11 from the outside of the adit. Cladosporium spp. were the fungi most frequently isolated from the internal atmosphere of the adit and from the external air. From the rock walls and from the rock debris on the floor of the adit only seven species of fungi were isolated. The fungi most frequently isolated from the rock walls were the Aspergillus niger group and from the rock debris we also found A. niger group along with species of Mucor. The concentration of airborne fungi in the adit did not exceed official limits and norms present for a health risk to the tourists, but fungi species isolated from the rocks can cause their degradation.     

The fungal flora of soft fruits in relation to storage and spoilage

The fungal population of freshly harvested strawberries, raspberries and blackberries was studied throughout the fruiting seasons and the relative importance of fungi responsible for spoilage of stored fruit from different harvest dates was assessed. Botrytis cinerea, Cladosporium spp., Penicillium spp., Aureobasidium pullulans and Mucor spp. were consistently present on all three fruits while Colletotrichum gloeosporioides and Didymella applanata were prevalent on raspberries only and Epicoccum purpurascens and Alternaria spp. on blackberries only. Botrytis cinerea and Mucor mucedo were the predominant spoilage organisms of all three fruits, although the relative importance of the two fungi changed as the season progressed, especially for strawberries. Rhizopus stolonifer, Cladosporium spp., Penicillium spp. and Colletotrichum gloeosporioides were only of minor importance as spoilage organisms.     

Yeasts and filamentous fungi carried by the gynes of leaf-cutting ants

Insect-associated microbes exhibit a wide range of interactions with their hosts. One example of such interactions is the insect-driven dispersal of microorganisms, which plays an essential role in the ecology of several microbes. To study dispersal of microorganisms by leaf-cutting ants (Formicidae: Attini), we applied culture-dependent methods to identify the filamentous fungi and yeasts found in two different body parts of leaf-cutting ant gynes: the exoskeleton and the infrabuccal pocket. The gynes use the latter structure to store a pellet of the ants’ symbiotic fungus during nest founding. Many filamentous fungi (n = 142) and yeasts (n = 19) were isolated from the gynes’ exoskeleton. In contrast, only seven filamentous fungi and three yeasts isolates were recovered from the infrabuccal pellets, suggesting an efficient mechanism utilized by the gynes to prevent contamination of the symbiotic fungus inoculum. The genus Cladosporium prevailed (78%) among filamentous fungi whereas Aureobasidium, Candida and Cryptococcus prevailed among yeasts associated with gynes. Interestingly, Escovopsis, a specialized fungal pathogen of the leaf-cutting ant-fungus symbiosis, was not isolated from the body parts or from infrabuccal pellets of any gynes sampled. Our results suggest that gynes of the leaf-cutter ants Atta laevigata and A. capiguara do not vertically transmit any particular species of yeasts or filamentous fungi during the foundation of a new nest. Instead, fungi found in association with gynes have a cosmopolitan distribution, suggesting they are probably acquired from the environment and passively dispersed during nest foundation. The possible role of these fungi for the attine ant–microbial symbiosis is discussed.     

Quantification of Alternaria,Cladosporium, Fusarium and Penicillium verrucosum in Conventional and Organic Grains by qPCR

We analysed the levels of Alternaria, Cladosporium, Fusarium and Penicillium verrucosum in grain samples harvested in 2011 and 2012 from conventional and organic farms using qPCR. In general, both Alternaria and Cladosporium occurred in all cereal grains in the highest quantities, followed by P. verrucosum and Fusarium. Alternaria, Cladosporium and P. verrucosum had the highest levels in crop mixtures, barley and rye and lower levels in wheat, while Fusarium levels were the highest in crop mixtures and wheat. The levels of Alternaria and P. verrucosum were higher in organic rye and wheat than conventional grains. Although the level of Fusarium was higher in conventional than organic rye, opposite results were obtained for crop mixtures. A positive correlation was found between Alternaria, Cladosporium and P. verrucosum, indicating that similar factors might affect the distribution of these fungi in grains.     

Patterns of change in secondary and tertiary sex ratios of the Terebrantian thrips,Frankliniella occidentalis

Adult sex ratios (tertiary sex ratios) of the haplo-diploid Terebrantian thrips species, Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae) were examined from several native and introduced hosts in an apple (Malus spp.) ecosystem. The ratios were variable and most were female-biased, ranging from 0 to 61% males. Populations in apple bud clusters during early bloom were female-biased (0–10% males). At later bloom states, populations were less female-biased in open blossom clusters (up to 33% males) compared with those in either unopened buds or older petalless blossoms (<11% males). Changes in tertiary sex ratio in all hosts were associated with changes in resource quality, suggesting a possible effect of host quality on sex allocation. In contrast, larval (secondary) sex ratios within apples were slightly male-biased (57%) with little change across apple bud reproductive stages or over time, indicating little to no differential sex allocation. Sex ratios of populations in flight were less female-biased than those found on plants in 62 of 65 comparisons, which suggests that males are more likely to be in flight relative to females. The evidence supports that differential dispersal and distribution of sexes toward various host qualities together with a shorter longevity of adult males determines the pattern of adult sex ratios rather than any significant differential sex allocation.     

Continually Measured Fungal Profiles in Sick Building Syndrome

Buildings with indoor air quality (IAQ) complaints frequently have high airborne concentrations of Penicillium species, while buildings with few IAQ complaints have an indoor air (IDA) fungal ecology similar to outdoor air (ODA), where Cladosporium species is usually the dominant microorganism. These studies compared fungal air profiles, measured continually over 6 h in a documented sick building, in IDA in a room experiencing IAQ problems with fungal profiles measured concurrently in ODA. The dominant species collected at both sites were Penicillium species, Cladosporium species, and Alternaria species. In the IDA, Penicillium species were always the dominant organisms, ranging from 150 to 567 cfu/m³ (89.8–100% of the total fungi). In the ODA, Cladosporium species were dominant in four samples (40.0–70.6%), while Penicillium species were dominant (52.7–79.6%) in two. These data demonstrate that, even though ODA fungal profiles are changing continuously, IDA fungal profiles in “sick” buildings tend to remain unchanged. Received: 6 July 1998 / Accepted: 12 August 1998