Conidia Count Research Articles

Effects of Pulsed Light on Mycelium Growth and Conidiation in Aspergillus oryzae

Understanding how Aspergillus oryzae responds to light is critical for developing efficient light regulation strategies in the brewing and waste treatment industries. Although continuous light is known to restrict A. oryzae, little is known about A. oryzae’s sensitivity to light with photoperiod. In this study, we used pulse wave modulation (PWM) to generate nine pulsed blue light (PBL) treatments with varying peak light intensities and frequencies. The effect of PBL on A. oryzae was then compared to that of continuous blue light (CBL). Our findings showed that A. oryzae GDMCC 3.31 mycelium developed faster and produced more conidia under PBL with specific peak intensities and frequencies than under CBL treatment when the light dose and average light intensity were held constant. The colony diameter and conidia count under the two PBL treatments (PL-20_40%_1 Hz and PL-400_20%_10 kHz) were 1.13 and 1.22 times greater than under the CBL treatments, respectively. This different response may be mainly attributed to A. oryzae’s adaptation to the light–dark cycles in nature. Furthermore, an interactive effect was found between peak light intensity and frequency. This work includes pulsed wave modulation as a new factor that influences the A. oryzae photoresponse and recommends it in the development of light regulation methods for fermentation.

Influence of Glyphosate in the Fungus Trichoderma Harzianum Coming from Rhizoctonia Solani in Huancayo 2019

The objective of this research is to determine the influence of glyphosate on the conidia count of the Trichoderma harzianum fungus grown under laboratory conditions. This fungus is found in all types of soil, but it is more important in those for agricultural use where they fulfill a beneficial function. Glyphosate is an herbicide widely used in the elimination of weeds and shrubs, its effect can be extended to beneficial fungi and its permanence in the soil exceeds the specifications in the data sheet. For this reason, the culture of T. harzianum is carried out under direct exposure with different concentrations of glyphosate, the average dose (1 ml) in the investigation arises from that recommended by the manufacturer of the product and four more are established, two major doses (1.25 ml and 1.50 ml) and two minor doses (0.50 ml and 0.75 ml). Data was collected using observation tokens. All doses were observed to decrease the number of conidia including the mean 1 ml dose producing a 54% reduction compared to the control sample. The doses of 1.25 ml and 1.50 ml reduce up to 65% and 81% respectively. Therefore, this herbicide negatively influences the growth of the fungus and consequently inhibits its beneficial actions.

Environmental factors impact temporal Passalora sequoiae conidia counts from Leyland cypress

AbstractNeedle blight disease, caused by Passalora sequoiae, results in a progressive loss of leaf tissue on Leyland cypress (×Cupressocyparis leylandii) within container and field tree nurseries, in the landscape and on Christmas tree farms. Fungicide schedules have been developed in response to seasonal symptom progression and conidia dispersion without clarification of the influence of weather conditions on disease. Conidia count data of P. sequoiae were collected approximately weekly from June to December in 2001 in Watkinsville, GA, and in 2002 in Dearing, GA. Peak conidia numbers were trapped in September and October. Daily weather data summaries were obtained from a weather station at each location. Deterministic models were developed individually for summer (1 June to 30 September) and fall (1 October to 21 December) seasons. A three‐day moving average (MA) of average daily temperature (avgT) had a positive quadratic relationship with conidia counts in the summer season. A 10‐day MA of avgT, vapour pressure deficit (VPD) and total solar radiation (SolR) had a positive quadratic, a negative linear and positive linear relationship, respectively, with conidia counts in the fall season. The models show that the seasonal shift to cooler fall temperatures, along with lower VPD and SolR, favour production and dispersal of P. sequoiae conidia.

Use of Green Fluorescent Protein-Expressing Aspergillus fumigatus conidia to Validate Quantitative PCR Analysis of Air Samples Collected on Filters

This study used green fluorescent protein (GFP)-expressing Aspergillus fumigatus conidia to compare quantitative PCR (qPCR) enumeration with direct epifluorescent microscopic filter counts of conidia collected on filters in a test chamber. In separate experiments this study initially compared white versus fluorescent light microscopy for counting A. fumigatus conidia, then compared fluorescent microscopy counting of corresponding filter halves, and finally compared qPCR enumeration to counting by fluorescent light microscopy. The use of GFP-expressing conidia with epifluorescent microscopy yielded significantly higher conidia counts (p = 0.026, n = 41, mean of 4.1 conidia per counting field) and 40% faster counting times when compared to conventional counting using white light microscopy. GFP-expressing conidia were aerosolized in a test chamber and collected onto filters. Filters were divided in half and GFP-expressing conidia enumerated. There was no significant difference in the average conidia count per field between corresponding filter halves (p = 0.3, n = 9 filters, mean of 7.8 conidia per counting field). Thus, one filter half could be counted optically and would provide a reliable estimate of filter loading of the corresponding half, which could then be analyzed by qPCR. Filters (n = 38) loaded with GFP conidia in the aerosol chamber were divided in half and analyzed by either fluorescent microscopy or qPCR. The estimated filter loadings ranged from 15–30,000 conidia per filter. There was a linear relationship with a nearly 1:1 ratio between qPCR and direct microscopic estimates of filter loading (y = 1.06× + 404; R 2 = 0.91) showing that the outlined qPCR analysis method is in agreement with an external reference method and is reliable for enumerating A. fumigatus conidia collected on filters. The comparative data derived using GFP-expressing conidia confirmed that qPCR provides sensitive and accurate quantification of DNA from airborne conidia collected on filters.

Integrated management of powdery mildew of mango in Egypt

Powdery mildew caused by Oidium mangiferae, is the most important disease of mango. Field surveys of five cultivars in five Governorates, revealed that incidence of infection was higher on cvs. Alphonso and Seddek than on Zebda, Hendi Besenara and Ewise. The highest disease incidence was recorded in El-Behera Governorate. The various environmentally friendly natural compounds as the biological control agents (BCAs) ( Verticillium lecanii, Bacillus subtilis and Tilletiopsis minor); mineral salt (phosphate solutions, KH 2PO 4); antitranspirant (kaolin) and antioxidant (ascorbic acid) applied independently or in mixtures as alternatives to chemical fungicides were evaluated for their efficacy in controlling mango powdery mildew in an integrated management system. Application of BCAs, kaolin alone and/or in combination with KH 2PO 4 in vitro to mango leaf disks before inoculation with O. mangiferae markedly decreased conidial germination and leaf infection. The largest decrease was obtained with combined treatments. In field trials during 2003 and 2004 in El-Noubaria using cvs. Alphonso and Seddek naturally infected by powdery mildew, each treatment, applied at 15 d intervals effectively controlled O. mangiferae on blossom clusters and fruit set. BCAs and kaolin treatments were superior in reducing powdery mildew infection. Blossom clusters and fruit set infection were inhibited by using a mixture of BCAs with kaolin and/or KH 2PO 4. Other tested compounds, such as ascorbic acid as a single treatment or in combination with other compounds showed some effectiveness in reducing disease severity. Mixtures of all four natural compounds were more effective in significantly reducing powdery mildew severity and conidia counts on blossom clusters and fruit set and increasing fruit set and yields on trees of both cultivars than mixtures of two or three or single applications. BCAs, mineral salts, antitranspirant and antioxidant in combinations could be used in an integrated management system to control powdery mildew in mango trees.

Investigation of Spray Application of Microbial Herbicides Using Alternaria alternata on Amaranthus retroflexus

Inclusion of Alternaria alternata conidia in a spray formulation affected the distribution pattern on the target. The dry weight of Amaranthus retroflexus plants was reduced by more than 83% when A. alternata conidia (107 ml -1 ) were applied at 200 L ha -1 or greater and when given a 24 h dew period. At low application volumes (25 or 50 L ha -1 ) plant dry weight was reduced by only 29 or 54%. After 7-8 h dew period, conidial germination on the leaf surface was 11-19%. This increased to 62-91% after 24 h dew period. Counts of conidia on leaves indicated that up to 86% of the conidia sprayed were not retained on the target plant, or did not reach it. This is reflected in lesion numbers per unit area being only 3-5% of the calculated theoretical numbers. The results cast doubt on the suitability of A. alternata as a microbial herbicide for the control of Am. retroflexus .