Airborne Spores Research Articles

Vertical transmission of fungal endophytes is widespread in forbs

To date, it has been thought that endophytic fungi in forbs infect the leaves of their hosts most commonly by air-borne spores (termed “horizontal transmission”). Here, we show that vertical transmission from mother plant to offspring, via seeds, occurs in six forb species (Centaurea cyanus, C. nigra,Papaver rhoeas,Plantago lanceolata,Rumex acetosa, and Senecio vulgaris), suggesting that this may be a widespread phenomenon. Mature seeds were collected from field-grown plants and endophytes isolated from these, and from subsequent cotyledons and true leaves of seedlings, grown in sterile conditions. Most seeds contain one species of fungus, although the identity of the endophyte differs between plant species. Strong evidence for vertical transmission was found for two endophyte species, Alternaria alternata and Cladosporium sphaerospermum. These fungi were recovered from within seeds, cotyledons, and true leaves, although the plant species they were associated with differed. Vertical transmission appears to be an imperfect process, and germination seems to present a bottleneck for fungal growth. We also found that A. alternata and C. sphaerospermum occur on, and within pollen grains, showing that endophyte transmission can be both within and between plant generations. Fungal growth with the pollen tube is likely to be the way in which endophytes enter the developing seed. The fact that true vertical transmission seems common suggests a more mutualistic association between these fungi and their hosts than has previously been thought, and possession of endophytes by seedling plants could have far-reaching ecological consequences. Seedlings may have different growth rates and be better protected against herbivores and pathogens, dependent on the fungi that were present in the mother plant. This would represent a novel case of trans-generational resistance in plants.

Distribution and Abundance of Airborne Palynomorphs in Aku, Enugu State, Nigeria

A study of airborne palynomorphs of Aku was carried out with the use of tauber pollen sampler from October to December, 2004. A total of 3,390 palynomorphs was recorded with the breakdown as follows: October, 1248; November, 1156 and December, 1526. Out of the counted palynomorphs, pollen grains constituted 2,125.The count of 736 pollen in October was followed by a decrease to 545 in November and a further increase to 844 in December. The pollen grains belonged to 20 families of flowering plants (17 dicotyledons and 3 monocotyledons) consisting of 20 genera. The result revealed dominance of wooded shrub grassland/woodland vegetation sub-type, relics of tropical lowland rainforest and secondary grassland. The taxa of both tropical lowland rainforest and secondary Grassland decreased from October to November and increased again in December. Fungi were the major spore contributors to the atmosphere and were dominated by the spores of S padicoides, Curvularia, Dreschlera/Helminthosporium and Nigrospora . Pollen grains were next to fungi in total abundance and were dominated by the pollen of; E laeis guineensis Jacq, Poaceae, Milicia excelsa Wild C.C. Berg, Irvingia wombolu Vermoesen, Syzygium guineense Engl. and Ageratum conyzoides L. December had a high influx of charred gramineae cuticles indicative of increased burning activities in the area. Fungal spores recorded per month had an inverse relationship with the monthly rainfall and relative humidity. Keywords : Distribution, Abundance, Airborne spore, Palynomorphs, Aku

Variation in Airborne Fungal Spore Concentrations in Four Different Microclimate Regions in Romania

Airborne fungal counts and types were examined in four regions from Romania. The aim of our study was to determine the concentrations of Alternaria, Cladosporium, Drechslera-type, Epicoccum and Nigrospora atmospheric fungal spores in urban areas: Braşov, Bucharest, Cluj-Napoca and Timişoara. Other objective of this study was to examine the relationships between atmospheric fungal spores and pollen. Few studies have confirmed the high frequency and concentrations for some of these spore types in Romania. The sampling sites differed in habitat characteristics, such as vegetation and microclimate. Airborne spores’ sampling was carried out using the Lanzoni volumetric sampler and during August 2008. The totals of airborne spores recorded in this study show a considerable variation. Cladosporium and Alternaria have been identified as the most abundant and frequent fungal aeroallergens in Timişoara and Bucharest. Drechslera-type, Epicoccum, and Nigrospora had very low values of spore count in all sites. Observations show that seven types of pollen appear regularly and few of these are in great abundance. Fungi are present in the air in concentrations considerably in excess of that of pollen grains. Ambrosia artemisiifolia is the most important pollen allergen in all of the sampled areas discussed here, especially in western country (Timişoara).

The lactic acid bacteria metabolite phenyllactic acid inhibits both radial growth and sporulation of filamentous fungi

BackgroundFood spoilage caused by molds is a severe problem. In food and feed, e.g. dairy products, sourdough bread and silage, lactic acid bacteria are used as starter cultures. Besides lactic and acetic acid, some strains produce other low molecular weight compounds with antifungal activities. One of these metabolites is phenyllactic acid (PLA), well known for its antifungal effect. The inhibitory effect of PLA has only partially been investigated, and the objective of this study was to elucidate in detail the antifungal properties of PLA.ResultsWe investigated the outgrowth of individual conidia from Aspergillus niger, Cladosporium cladosporioides and Penicillium roqueforti, and observed the morphologies of resulting colonies on solid media using different acid concentrations. We found that PLA inhibits molds similar to weak acid preservatives. Furthermore, it has an additional activity: at sub-inhibitory concentrations, fungal colonies displayed slower radial growth and inhibited sporulation. The L isoform of PLA is a more potent inhibitor than the D form. Increased expression of phiA was observed during PLA treatment. This gene was initially identified as being induced by Streptomyces-produced macrolide antibiotics, and is shown to be a structural protein in developed cells. This suggests that PhiA may act as a general stress protectant in fungi.ConclusionFrom a food protection perspective, the results of this study support the usage of lactic acid bacteria strains synthesizing PLA as starter cultures in food and feed. Such starter cultures could inhibit spore synthesis, which would be beneficial as many food borne fungi are spread by airborne spores.

A selective medium to isolate airborne spores of Microdochium nivale, causing winter wheat scab

Winter wheat scab in Hokkaido, Japan is caused predominantly by Gibberella zeae and Microdochium nivale and can result in significant yield losses. A selective medium for isolation of G. zeae was previously developed, but not for M. nivale. The purpose of this study therefore was to develop a selective medium for isolation of airborne spores of M. nivale. Based on the basic composition of Komada’s Fusarium-selective medium, carbon and nitrogen sources and the most suitable vitamin B component for the basal composition were examined. Hyphal growth of M. nivale was promoted when galactose was replaced with lactose and combined with L-asparagine, while aerial hyphal formation increased with thiamine hydrochloride as the vitamin B source. In antimicrobial composition, colony formation of other filamentous fungi was greatly inhibited by spiroxamine. Thiophanate methyl, to which M. nivale shows resistance, selectively inhibited the growth of Fusarium spp. only. Spore trapping using the selective medium was subsequently performed in a wheat field. M. nivale formed characteristic pinkish colonies on the selective medium in the case of contamination with other filamentous fungi, making differentiation easy. Overall, the findings show that LATTS medium developed in this study is effective for isolation of airborne spores of M. nivale.

Temporal dynamics of airborne fungi in Havana (Cuba) during dry and rainy seasons: influence of meteorological parameters

The aim of this paper was to determine for first time the influence of the main meteorological parameters on the atmospheric fungal spore concentration in Havana (Cuba). This city is characterized by a subtropical climate with two different marked annual rainfall seasons during the year: a "dry season" and a "rainy season". A nonviable volumetric methodology (Lanzoni VPPS-2000 sampler) was used to sample airborne spores. The total number of spores counted during the 2 years of study was 293,594, belonging to 30 different genera and five spore types. Relative humidity was the meteorological parameter most influencing the atmospheric concentration of the spores, mainly during the rainy season of the year. Winds coming from the SW direction also increased the spore concentration in the air. In terms of spore intradiurnal variation we found three different patterns: morning maximum values for Cladosporium, night peaks for Coprinus and Leptosphaeria, and uniform behavior throughout the whole day for Aspergillus/Penicillium."

Airborne basidiospores of Coprinus and Ganoderma in a Caribbean region

The present study sought to examine Coprinus and Ganoderma airborne spore counts, analysing seasonal variations, the influence of meteorological variables and intraday behaviour with a view to charting the aerobiological dynamics of both genera in Havana (Cuba) during a 2-year period (November 2010–October 2012). A Hirst-type volumetric air sampler was used as sampling methodology. The spores registered in the air were identified and counted following the model proposed by the Spanish Aerobiological Network based on two longitudinal transects along the slides. Coprinus spores outnumbered those of the Ganoderma (28,468 annual total spores vs. 1,921 spores). Moreover, both genera were recorded in the atmosphere on a large number of days over the two-year study period, with daily maximum concentrations in the rainy months. The daily maximum value for Coprinus was 880 spores/m3 (30 September 2011), whereas for Ganoderma 44 spores/m3 (4 September 2011). The analysis of the Spearman correlation coefficient showed a significant positive correlation of the airborne Coprinus and Ganoderma spores with the temperature, relative humidity and rainfall, whereas the degree of association is negative with the wind speed. Regarding the intraday behaviour, both basidiospores were more abundant in the atmosphere during the night, with a maximum peak at 5–6 a.m.

Role of ascospores and conidia in the initiation and spread of South American leaf blight in a rubber tree plantation

Microcyclus ulei, the fungus causing South American leaf blight (SALB) on rubber tree leaves, produces two main types of spores: ascospores and conidia. To assess their respective epidemiological role, a field experiment was conducted in French Guiana over 3 years. Tree phenology, disease severity and climate variables were recorded while airborne spores were trapped and quantified. Ascospores were shown to play an essential role in the perpetuation of the disease outside the host's growth periods, in the resumption of epidemics, and in the spread of the disease to disease‐free zones. Conidia were trapped in visibly infected plots only, during periods of host growth. Disseminated over short distances and present only temporarily on leaves, the conidia enabled the disease to spread stepwise when the climate was conducive. Segmentation analysis revealed that the duration of high relative humidity was the climatic variable most related to ascospore trapping. Ascospore release did not require low temperatures. Considering the essential role of the ascospores in the initiation and spread of disease, artificial defoliation as a means of reducing the inoculum pressure during tree refoliation is proposed to control SALB. To check the validity of this method, a survey over several years of natural defoliation–refoliation in relation to climate and other leaf diseases is needed.

Mycological study for a management plan of a neotropical show cave (Brazil)

Caves are stable environments with characteristics favoring the development of microorganisms. The allocthonous input of organic matter and microbes into the warm Neotropical caves may favor the development of filamentous fungi, including pathogenic species. Histoplasma capsulatum is a pathogenic species commonly found in caves and associated with bat and bird guano. Many Brazilian caves have been historically visited due to scenic and religious tourism. The objective of this study was to perform a microbiology study for a management plan of a show cave in Brazil, focusing on the presence and distribution of pathogenic and opportunistic fungi in the cave. Statistics analysis was used to verify the influence of touristic activity on air-borne fungi spore load. Fungi were isolated from air and guano in Lapa Nova Cave. Samples were obtained through serial dilution, direct and settle plate techniques. For H. capsulatum, samples were incubated in specific media and conditions. Air-borne fungal spore load was compared prior and during visitation and statistically analyzed. A total of 2,575 isolates from the genera Aspergillus, Calcarisporium, Chaetomium, Cladosporium, Curvularia, Emericella, Eurotium, Fusarium, Geotrichum, Gliocladium, Mucor, Purpureocillium, Paecilomyces, Penicillium, Rhizopus and Trichoderma were identified. Histoplasma capsulatum was not isolated from the cave. Eleven opportunistic species were identified. Significant (p<0.05) variations on fungal richness in the air occurred due to cave visitation. Areas of potential microbiologic risks were indicated and management actions suggested. The results suggest a diverse community inhabiting the cave. Possible opportunistic species should be monitored in show caves and microbiota should always be included in the elaboration of cave management plans. This is the first detailed microbiologic study for a management plan of a show cave in the country. It provides relevant information for future management plans.

The RodA Hydrophobin on Aspergillus fumigatus Spores Masks Dectin-1– and Dectin-2–Dependent Responses and Enhances Fungal Survival In Vivo

Aspergillus and Fusarium species are important causes of fungal infections worldwide. Airborne spores (conidia) of these filamentous fungi express a surface protein that confers hydrophobicity (hydrophobin) and covers cell wall components that would otherwise induce a host immune cell response. Using a mutant Aspergillus fumigatus strain (ΔrodA) that does not express the RodA hydrophobin, and Aspergillus and Fusarium conidia from clinical isolates that were treated with hydrofluoric acid (which removes the A. fumigatus RodA protein), we observed increased surface exposure of β1,3-glucan and α-mannose on Aspergillus and Fusarium conidia. We also found that ΔrodA and hydrofluoric acid-treated conidia stimulate significantly higher NF-κB p65 nuclear translocation and cytokine production by macrophages from C57BL/6, but not from Dectin-1(-/-) or Dectin-2(-/-) mice. Using a murine model of A. fumigatus corneal infection, we showed that ΔrodA conidia induced significantly higher cytokine production, neutrophil infiltration, and more rapid fungal clearance from C57BL/6 corneas compared with the parent G10 strain, which was dependent on Dectin-1 and Dectin-2. Together, these findings identify the hydrophobin RodA as a virulence factor that masks Dectin-1 and Dectin-2 recognition of conidia, resulting in impaired neutrophil recruitment to the cornea and increased fungal survival and clinical disease.

Occupational Exposure to Aflatoxin B1 in Swine Production and Possible Contamination Sources

Although the adverse health consequences of ingestion of food contaminated with aflatoxin B1 (AFB1) are known, relatively few studies are available on the adverse effects of exposure in occupational settings. Taking this into consideration, our study was developed aiming to elucidate the possible effects of occupational exposure to AFB1 in Portuguese swine production facilities using a specific biomarker to assess exposure to AFB1. In total, 28 workers participated in this study, providing blood samples, and a control group (n = 30) was composed of subjects without any type of agricultural activity. Fungal contamination was also studied by conventional methods through air, surfaces, and new and used floor coverage. Twenty-one workers (75%) showed detectable levels of AFB1 with values ranging from <1 ng/ml to 8.94 ng/ml and with a mean value of 1.91 ± 1.68 ng/ml. In the control group, the AFB1 values were all below 1 ng/ml. Twelve different Aspergillus species were identified. Aspergillus versicolor presented the highest airborne spore counts (3210 CFU/m3) and was also detected in higher values in surfaces (>300 CFU/cm2). Data indicate that exposure to AFB1 occurs in swine barns, and this site serves as a contamination source in an occupational setting.

Are endophytes an important link between airborne spores and allergen exposure?

Grasses represent one of the Earth’s most common plant groups, and natural and cultivated habitats dominated by grasses cover about 40% of the land surface. In turn, each grass species hosts multiple fungal species which can behave as endophytes. An analysis of the endophytic taxa identified in surveys conducted in 14 grass species showed that some of the most frequent taxa on each grass were also present across several host grasses. These taxa were Alternaria, Epicoccum, Cladosporium, Fusarium, and a few others. A similar analysis of airborne fungi surveyed at 41 different locations throughout the world showed that some of the most geographically widespread, and most locally frequent airborne fungi belonged to the same genera that are dominant endophytes in grasses (i.e. Cladosporium, Alternaria, Fusarium, etc.). Therefore, airborne spores of genera that are ubiquitous in grasses are common worldwide and attain high atmospheric concentrations. In addition, spores of the above mentioned fungi are also important respiratory allergens. Direct observation indicates that saprobic colonization and sporulation of non-systemic grass endophytes could become unrestrained when their host plant tissue dies. Subsequently, when appropriate environmental conditions favour sporulation on grass host surfaces, the natural cycle for airborne conidia initiates, and large numbers of these conidia disperse as inoculum for new endophytic infections. Therefore, the cycle of endophytism may be an important link between climate, plant biology and public health.

Microsite Factors and Spore Dispersal Limit Obligate Mycorrhizal Fern Distribution: Habitat Islands ofBotrychium pumicola(Ophioglossaceae)

Abstract We investigated the influence of microsite and establishment factors on the distribution of Botrychium pumicola Coville ex Underw. (Ophioglossaceae), an obligate mycorrhizal fern restricted to specialized volcanic habitats, predominately pumice, in the Cascade Range of central and southern Oregon and northern California. The fragmented distribution of this threatened species and its absence from suitable habitat is of conservation concern. At eight subalpine and one alpine site, plots with and without B. pumicola were compared for biotic and abiotic variables. Botrychium pumicola populations occurred with diverse perennial plants. Nearest neighbor analysis showed a clumped dispersion of B. pumicola with associated plants. Botrychium pumicola spores were found in soils of seven plots with and two without B. pumicola. In plots with B. pumicola, soil potassium was higher while soil density and soil temperatures were lower than in plots without B. pumicola. Airborne spores, collected in spore traps, ...

Cladosporium airborne spore incidence in the environmental quality of the Iberian Peninsula

Cladosporium spores are ubiquitous in the air and are included in the fungal contaminants that define environmental quality. This paper provides an updated review of their concentration in the Iberian Peninsula, based on data from 12 sampling stations collected using a common non-viable volumetric sampling method and the same subsequent data-treatment techniques. The database comprised 84 annual periods, covering the period 1993–2009. Mean annual total spore concentrations for each station, calculated as the sum of daily concentrations, ranged from 54 459 in Cartagena to 933 485 in Sevilla; other sampling stations recorded annual total spores between 93 052 (Porto) and 579 953 (Mérida). Analysis of annual spore-distribution patterns revealed either one or two peaks (spring and fall) depending on the location and prevailing climate of the area where the sampling stations have been placed. For all stations, average temperature was the meteorological parameter displaying the strongest positive correlation with airborne spore concentrations.

Ascending Aortic Graft Thrombosis and Diffuse Embolization From Early Endoluminal Aspergillus Infection

We present a 43-year-old man who underwent emergent replacement of the ascending aorta for type A dissection and hemiarch reconstruction with a 28-mm prosthetic graft. Dramatic neurologic symptoms, renal failure, and bowel ischemia developed on postoperative day 5. A computed tomography scan showed a large floating thrombus in the ascending aortic graft and massive peripheral embolization throughout the body.

Occupational Exposure to Aspergillus by Swine and Poultry Farm Workers in Portugal

Aspergillus is among a growing list of allergens that aggravate asthmatic responses. Significant pulmonary pathology is associated with Aspergillus-induced allergic and asthmatic lung disease. Environments with high levels of exposure to fungi are found in animal production facilities such as for swine and poultry, and farmers working with these are at increased risk for occupational respiratory diseases. Seven Portuguese poultry and seven swine farms were analyzed in order to estimate the prevalence, amount, and distribution of Aspergillus species, as well as to determine the presence of clinical symptoms associated with asthma and other allergy diseases in these highly contaminated settings. From the collected fungal isolates (699), an average incidence of 22% Aspergillus was detected in poultry farms, while the prevalence at swine farms was 14%. The most frequently isolated Aspergillus species were A. versicolor, A. flavus, and A. fumigatus. In poultry farms, A. flavus presented the highest level of airborne spores (>2000 CFU/m3), whereas in swine farms the highest was A. versicolor, with an incidence fourfold greater higher than the other mentioned species. Eighty workers in these settings were analyzed, ranging in age from 17 to 93 yr. The potentially hazardous exposure of poultry workers to mold allergens using sensitization markers was evaluated. Although no significant positive association was found between fungal contamination and sensitization to fungal antigens, a high incidence of respiratory symptoms in professionals without asthma was observed, namely, wheezing associated with dyspnea (23.8%) and dyspnea after strenuous activities (12.3%), suggesting underdiagnosed respiratory disturbances. Further, 32.5% of all exposed workers noted an improvement of respiratory ability during resting and holidays. From all the analyzed workers, seven were previously diagnosed with asthma and four reported the first attack after the age of 40 yr, which may be associated with their occupational exposure. Some of the fungi, namely, the Aspergillus species detected in this study, are known to induce hypersensitivity reactions in humans. This study confirmed the presence and distribution of Aspergillus in Portuguese poultry and swine farms, suggesting a possible occupational health problem and raising the need for preventive and protective measures to apply to avoid exposure in both occupational settings.

Disinfection of airborne spores of Penicillium expansum in cold storage using continuous direct current corona discharge

Penicillium expansum is the most important fungal species that causes spoilage in cold-stored pome and stone fruits. P. expansum produces patulin, a toxic secondary metabolite. In this study, the mechanism and the potential of continuous direct-current corona discharge for the disinfection of P. expansum spores were explored. This may be a promising new technique to fight postharvest mould rots during cold storage. The changes in morphology and microstructure of P. expansum spores were characterised using scanning electron microscopy (SEM) and transmission electron microscopy (TEM), for both untreated spores and spores subjected to this corona discharge treatment. SEM and TEM revealed noticeable defects in the morphology and internal sub-structure of the spores after treatment. The mechanisms by which the corona discharge kills P. expansum spores are suggested to be these defects. A model was developed to simulate the inactivation kinetics under various corona discharge conditions. The model comprised a set of three ordinary differential equations derived from a hypothetical three-step reaction process. The model developed described the experimentally determined inactivation kinetics of the corona discharge disinfection of P. expansum spores well (the correlation coefficients r2 exceeded 0.919 in all cases). The relationship between the reciprocal of the square root functions of the corona energy density and the time taken to inactivate 90% of the spores in a population was linear (r2 = 0.987).

Species and organ specificity of fungal endophytes in herbaceous grassland plants

Summary1. aFoliar endophytic fungi in herbaceous plants are known to be diverse, yet studies characterizing the fungal communities in roots and shoots of plants across time are absent. These fungi are supposedly ubiquitous in nature, infecting plants through airborne spores. As many foliar endophytes can also exist in soil, we hypothesized that there would be a strong similarity between root and shoot endophytes in any given plant species and that differences between plant species would be greater than those between organs within a species.2. Leaf and root fungal endophyte communities were assessed in field‐collected plants of three co‐occurring grassland forbs (Cirsium arvense, Plantago lanceolata and Rumex acetosa) in two contrasting seasons (winter and summer). The former two species are mycorrhizal, whilst the latter species is not so.3. The highest fungal species richness was recorded from P. lanceolata with R. acetosa hosting the least endophyte diversity. Endophyte communities were more diverse in root than leaf tissues and in summer than in winter. Similarity of endophyte communities between different host plant species and organs within an individual host was very low. Negative correlations were found between mycorrhizal colonization and endophyte presence in the roots of C. arvense and P. lanceolata, suggesting some degree of antagonism or competition between the fungi. Consistent positive associations were found between the number of endophyte species in roots and shoots of plants.4. Synthesis. In contrast to previous studies, the results show that many endophytes do not occur ubiquitously, but instead exhibit both plant and tissue specificity. There is a strong seasonal change in endophyte communities, but the differences between roots and shoots at any one time can be just as large. This dissimilarity suggests a lack of systemic growth by the fungi from one tissue to another. Mycorrhizas may interact negatively with other root endophytes, indicating that the latter should not be ignored in future mycorrhizal studies. We should begin to think of individual plants as ecosystems of interacting microbes, whose community is structured by plant genetics and environmental conditions, coupled with interactions between the microbes themselves.

Spatial and temporal distribution of Alternaria spores in the Iberian Peninsula atmosphere, and meteorological relationships: 1993–2009

This paper provides an updated of airborne Alternaria spore spatial and temporal distribution patterns in the Iberian Peninsula, using a common non-viable volumetric sampling method. The highest mean annual spore counts were recorded in Sevilla (39,418 spores), Mérida (33,744) and Málaga (12,947), while other sampling stations never exceeded 5,000. The same cities also recorded the highest mean daily spore counts (Sevilla 109 spores m(-3); Mérida 53 spores m(-3) and Málaga 35 spores m(-3)) and the highest number of days on which counts exceeded the threshold levels required to trigger allergy symptoms (Sevilla 38 % and Mérida 30 % of days). Analysis of annual spore distribution patterns revealed either one or two peaks, depending on the location and prevailing climate of sampling stations. For all stations, average temperature was the weather parameter displaying the strongest positive correlation with airborne spore counts, whilst negative correlations were found for rainfall and relative humidity.

The role of rhizospheric Aspergillus flavus in standing maize crop contamination in different ecological zones of Khyber Pakthunkhwa, Pakistan

Soil and un-husked maize samples were collected from 29 different locations belonging to three distinct ecological zones (Swat, Hazara and Peshawar) of Khyber Pakhtunkhwa, Pakistan. The samples were evaluated for the incidence of aflatoxigenic strains of Aspergillus flavus. The soil samples collected from Peshawar (100%) and Hazara (66%), and grain samples collected from Swat (64%) and Peshawar (55%) were severely infected with aflatoxigenic strains of A. flavus. The strains isolated from maize kernels of Manyar, Jalala (Swat zone), Palosi and Takkar (Peshawar zone) produced the highest amount of aflatoxin B1 (324 to 514 µg g -1 ) and B2 (23 to 486 µg g -1 ). Similarly, the strains isolated from soils of Bannu (Peshawar) and Huripur (Hazara) were prominent in B1 (662 to 1323 µg g -1 ) and B2 (145 to 826 µg g -1 ). Microbial analysis of the surface sterilized grains showed that the strains isolated from Jalala (Swat) and Palosi (Peshawar) samples were high in B1 (62 to 79 µg g -1 ) and B2 (21 to 36 µg g -1 ). It was concluded, therefore, that A. flavus from soil might contaminate maize crop, but not directly from the same field. The most probable contamination occurred through air borne spores. It is thus recommended that protection from air borne spore should be devised.