Application of the Best Techniques to Reduce the Percentage of Storage Fungi in Peanut Seeds Arachis hypogaea

This study was conducted during the season 2019-2020 with the aim of testing the efficiency of some techniques to eliminate or reduce the frequency of storage fungi, namely Aspergillus flavus, A. niger, and Penicillium italicum naturally contaminating peanuts seeds. The seed sample was treated by soaking in hot water (50˚c, 60˚c, 70˚c), soaking in salt water at concentrations 10%, 15%, 20%, roasting in an ordinary oven at 150˚c for 10, 20 and 30 min, and roasting in a microwave oven at 100˚c for 1, 3, 5 and 7 min. The frequency of fungi occurrence percentage was estimated in seeds after treatments and incubation on the nutrient medium Potato Sucrose Agar (PSA). The results indicated the efficiency of all the techniques used in reducing the frequency of fungi in the treated seeds, as the fungus P. italicum was the most sensitive fungus under all techniques, and the study proved the superiority of the treatment by microwave roasting over the rest of the techniques, as it eliminated all the fungi carried in the seed by 100% when the duration of time used is 5 minutes.

Essential Oil Compositions and Antifungal Activity of Sunflower (Helianthus) Species Growing in North Alabama

Helianthus species are North American members of the Asteraceae, several of which have been used as traditional medicines by Native Americans. The aerial parts of two cultivars of Helianthus annuus, “Chianti” and “Mammoth”, and wild-growing H. strumosus, were collected from locations in north Alabama. The essential oils were obtained by hydrodistillation and analyzed by gas chromatography—mass spectrometry. The Helianthus essential oils were dominated by monoterpene hydrocarbons, in particular α-pinene (50.65%, 48.91%, and 58.65%, respectively), sabinene (6.81%, 17.01%, and 1.91%, respectively), β-pinene (5.79%, 3.27%, and 4.52%, respectively), and limonene (7.2%, 7.1%, and 3.8%, respectively). The essential oils were screened against three opportunistic pathogenic fungal species, Aspergillus niger, Candida albicans, and Cryptococcus neoformans. The most sensitive fungus was C. neoformans with minimum inhibitory concentration (MIC) values of 78, 156, and 78 μg/mL, respectively.

Antifungal Activity and Phytotoxicity of Vitex simplicifolia Oliv. Leaves Essential Oil

Agriculture faces many difficulties related to phytopathogenic fungi leading to quantitative and qualitative losses of crops. The use of essential oils against these fungi is one of the alternatives. This study focused on the antifungal activity and phytotoxicity of Vitex simplicifolia Oliv. leaves essential oil. Firstly, we extracted the essential oil from the leaves by hydrodistillation. Subsequently, seven fungal isolates were evaluated for their sensitivity to the essential oil on Potato Dextrose Agar (PDA) media at 0.1; 0.25 and 0.50%. Evaluation of the phytotoxicity of the essential oil was performed on sorghum seeds on a sterilized sand substrate. At the seventh day after incubation, the most sensitive fungi to the essential oil are Fusarium moniliforme, Colletotrichum graminicola and Curvularia lunata. The most sensitive fungus to the essential oil at 0.50% is Colletotrichum graminicola with 77.21% inhibition rate at the seventh day after incubation. Phytotoxicity evaluation showed that for all biomass parameters measured there is no significant difference between treatment with the essential oil and treatment with the fungicide control. At the end of this study, it appears that Vitex simplicifolia essential oil has a high antifungal activity. This essential oil has not shown toxicity on sorghum growth parameters. Therefore, this oil can be used in organic farming.

Functionalized para-substituted benzenes as 1,8-cineole production modulators in an endophytic Nodulisporium species

A Nodulisporium species (designated Ti-13) was isolated as an endophyte from Cassia fistula. The fungus produces a spectrum of volatile organic compounds (VOCs) that includes ethanol, acetaldehyde and 1,8-cineole as major components. Initial observations of the fungal isolate suggested that reversible attenuation of the organism via removal from the host and successive transfers in pure culture resulted in a 50 % decrease in cineole production unrelated to an overall alteration in fungal growth. A compound (CPM1) was obtained from Betula pendula (silver birch) that increases the production of 1,8-cineole by an attenuated Ti-13 strain to its original level, as measured by a novel bioassay method employing a 1,8-cineole-sensitive fungus (Sclerotinia sclerotiorum). The host plant produces similar compounds possessing this activity. Bioactivity assays with structurally similar compounds such as ferulic acid and gallic acid suggested that the CPM1 does not act as a simple precursor to the biosynthesis of 1,8-cineole. NMR spectroscopy and HPLC-ES-MS indicated that the CPM1 is a para-substituted benzene with alkyl and carboxyl substituents. The VOCs of Ti-13, especially 1,8-cineole, have potential applications in the industrial, fuel and medical fields.

Relative fungal efficacy results from the soil block test with a long incubation period of three commercial copper wood preservatives

Development of new wood preservative systems is a lengthy and expensive endeavor. This study examined soil block experiments with a longer incubation time than typical to make the test harsher, using commercial particulate copper azole (PCA), soluble copper azole (CA-C), and soluble alkaline copper quaternary (ACQ-D) systems. Both the CA-C and PCA systems performed poorly compared to ACQ-D with two copper tolerant fungi, even at retentions well above the specified ground-contact residential level, i.e., Use Category 4A (UC4A). With the one copper sensitive fungus examined, PCA and ACQ-D prevented decay at about half the UC4A retention. To compare these laboratory efficacy results, data from an outdoor accelerated post test with a copper tolerant fungus gave efficacies of ACQ > CA-C >> PCA, with PCA having significantly more decay than the two soluble copper systems. Further confirmation was obtained from recently published E7 stake data conducted at a site with extensive copper tolerant fungi, which suggested that ACQ performed better than PCA and CA-B after about 3 years of exposure in agreement with the harsh soil block results with the two copper-tolerant fungi. Conversely, results from four other sites without a history of extensive copper tolerant fungi are interpreted that all three systems generally performed adequately, which is compatible with the soil block test with the one copper sensitive fungus examined.

FsFKS1, the 1,3-β-Glucan Synthase from the Caspofungin-Resistant Fungus Fusarium solani

ABSTRACT The cell wall, a mesh of carbohydrates and proteins, shapes and protects the fungal cell. The enzyme responsible for the synthesis of one of the main components of the fungal wall, 1,3-β-glucan synthase, is targeted by the antifungal caspofungin acetate (CFA). Clinical isolates of Candida albicans and Aspergillus fumigatus are much more sensitive to CFA than clinical isolates of Fusarium species. To better understand CFA resistance in Fusarium species, we cloned and sequenced FsFKS1, which encodes the Fusarium solani f. sp. pisi β(1,3)-d-glucan synthase, used RNA interference to reduce its expression and complemented deletion of the essential fks gene of the CFA-sensitive fungus A. fumigatus with FsFKS1. Reduction of the FsFKS1 message in F. solani f. sp. pisi reduced spore viability and caused lysis of spores and hyphae, consistent with cell wall defects. Compensating for the loss of A. fumigatus fks1 with FsFKS1 caused only a modest increase in the tolerance of A. fumigatus for CFA. Our results suggest that FsFKS1 is required for the proper construction of F. solani cell walls and that the resistance of F. solani to CFA is at best only partially due to resistance of the FsFKS1 enzyme to this antifungal agent.

Inhibition de champignons phytopathogènes par des bactéries isolées du sol et de la rhizosphère de légumineuses

The antifungal activity of 644 bacterial isolates obtained from soil and from the rhizosphere of some leguminous plants was studied with one hyperparasite and six pathogenic fungi frequently associated with leguminous or gramineous plants. More than half (51.2%) of the bacterial isolates inhibited at least one fungus and 1.7% had an inhibitory effect on all the fungi tested. Stemphylium sarcinaeforme was the most sensitive fungus (inhibited by 27.0% of the bacteria tested), while Fusarium solani and Gliocladium roseum were the most resistant (inhibited by only 7.6 and 7.8% of the isolates, respectively). Verticillium albo-atrum and Fusarium oxysporum f. sp. medicaginis, important pathogens of alfalfa, were inhibited by 17.7 and 14.7% of the bacteria, respectively. Among the 166 bacteria showing the most important inhibitory effect on fungi, 7.2% inhibited strain A2 of Rhizobium meliloti and 21.1%, strain S14. In general, we obtained higher percentages of bacteria inhibiting fungi and Rhizobium meliloti from rhizospheric than from nonrhizospheric soil. When incorporated in the growth medium, some Pseudomonas spp. and Bacillus spp. reduced the growth surface of the tested fungi by more than 90%. Some bacteria reduced the mycelium density rather than the growth surface.

Actinomycètes antagonistes de champignons et n'affectant pas le Rhizobium meliloti

The effects of 481 actinomycetes isolated from agricultural soils supporting good growth of alfalfa or clover on two efficient strains of Rhizobium meliloti A2 and S14 were studied. Strain A2 was inhibited by 28% of the isolates and strain S14 was inhibited by 31% of them. No significant difference was found between the resistance of both actinomycete strains. The effects of the 288 isolates not affecting R. meliloti on six fungi were also studied. The most sensitive fungus was Stemphylium sarcinaeforme inhibited by 20% of the isolates, while Fusarium culmorum was the most resistant fungus and was inhibited by only 6% of the isolates. Thirteen isolates inhibited four to six fungi. In an autoclaved greenhouse soil, isolate 181 which inhibited the six fungi tested significantly reduced the population of the phytopathogenic fungus F. oxysporum f. sp. medicaginis and eliminated the inhibitory effect showed by this fungus on strain A2 of R. meliloti.