A. Y. Abdel-Mallek

MICROBIAL POPULATIONS AND ENZYME ACTIVITY IN SOIL TREATED WITH HEAVY METALS

Effects of two concentrations (200 and 2000μg g−1 soil) of two heavy metals (copper and zinc as sulphates) applied to clay or sandy soil for 12 weeks on the total counts of fungi, bateria and actinomycetes were studied. Activities of three soil enzymes (urease, nitrate reductase and amidase) were also investigated. Application of heavy metals to the clay soil reduced the microbial populations. However, although neither heavy metal showed any significant increasing effect on microorganisms populations in clay soil samples, some stimulatory effects were noted in sandy soil. Activities of urease and nitrate reductase were inhibited by heavy metal application in both soils. Amidase activity was inhibited only with the higher application rate after some experimental periods.

Studies on fungi associated with tomato fruits and effectiveness of some commercial fungicides against three pathogens

Among 39 fungal species and one variety belonging to 16 genera isolated from 116 healthy tomato fruits collected from markets in Assiut, Egypt, during 1994,Aspergillus niger was found to be the most prevalent, being isolated from 84.6% of the samples. Of 11 species recovered from 156 diseased tomatoes,Alternaria alternata, Rhizopus stolonifer andA. niger were the most common and isolated from 52.7%, 35.9% and 25.0% of the samples, respectively. Experiments for comparison of the effects of medium containing tomato juice with synthetic medium on the mycelial growth of nine fungal species indicated that, the tomato juice medium was more suitable for growth of all fungal species. The effect of five commercial fungicides and sodium hypochlorite when applied as post-harvest dips after inoculation was studied in laboratory againstA. alternata, A. niger andR. stolonifer. At 10 and 100 µg ml−1, neither of the fungicide caused a noticeable inhibition ofAlternaria rot. At 1000 µg ml−1 benlate, rovral and sumisclex completely preventedAlternaria andAspergillus rot, whereas cuprosan and ridomil were ineffective against rotting caused byA. niger. Rhizopus rot development was inhibited by over 50% with one treatment only (rovral at 1000 µg ml−1). Sodium hypochlorite has good curative properties against fruit rots especially those caused byA. alternata andA. niger.

Effect of soil treatment with the organophosphorus insecticide Profenfos on the fungal flora and some microbial activities

Tests were conducted to determine the effects of Profenfos [(0-(4-bromo-2-chlorophenyl) 0-ethyl S-n-propyl-phosphorothioat] on fungal populations and some activities in soil. Profenfos (at 5.4 micrograms active ingredient/g dry soil), has a significant adverse effect on the count of total fungi after 2, 4 and 6 weeks after treatment. This effect was completely alleviated after longer incubation. Incorporation of this insecticide into the agar medium inhibited the total count of soil fungi at 6.4 and 38.4 micrograms ml-1. Initial activation followed by a decrease in CO2 output occurred in soil treated with 5.4 micrograms a.i./g. The two doses of Profenfos accelerated urease activity for 6 weeks after soil treatment, but inhibited the enzyme activity after longer periods. An inhibitory effect on nitrate reductase activity was observed with some insecticide treatments in the early stages of incubation followed by an activation in certain cases.

Effect of glyphosate on fungal population, respiration and the decay of some organic matters in Egyptian soil

Glyphosate (Roundup), when applied to the soil usually did not exert any significant effect on the total count of soil fungi after all periods of the experiment except after 6 and 10 weeks where the count was inhibited by the two doses used (1.84, 9.2 mg active ingredient/kg dry soil). When the herbicide was incorporated into the agar medium the count of total fungi, Acremonium strictum and Aspergillus fumigatus was significantly increased by the two doses used and of Penicillium glabrum by the high dose only. However, P. funiculosum was completely eliminated by the high dose. Oxygen consumption in soil treated with glyphosate was significantly inhibited by the high dose after 2 weeks and by the two doses after 6, 8 and 10 weeks. Glyphosate exerted two significant effects of stimulation and inhibition on the rate of the decay of stem segments of three plants at certain treatments of dose and time.

Pathogenicity of Beauveria bassiana and Metarhizium anisopliae against Galleria mellonella

The greater wax moth Galleria mellonella L. (Lepidoptera: Pyralidae) is occasionally found in beehives and is a major pest of stored wax. Entomopathogenic fungi have recently received attention as possible biocontrol elements for certain insect pests. In this study, 90 isolates of Beauveria bassiana and 15 isolates of Metarhizium anisopliae were screened for proteases and lipases production. The results showed significant variations in the enzymatic action between the isolates. In the bioassay, the selected isolates evinced high virulence against the 4th instar of the G. mellonella larvae. The isolates BbaAUMC3076, BbaAUMC3263 and ManAUMC3085 realized 100% mortality at concentrations of 5.5 × 106 conidia ml−1, 5.86 × 105 conidia ml−1, and 4.8 × 106 conidia ml−1, respectively. Strong enzymatic activities in vitro did not necessarily indicate high virulence against the tested insect pest. The cuticle of the infected larvae became dark and black-spotted, indicating direct attack of fungus on the defense system of the insects. The LC50 values were 1.43 × 103, 1.04 × 105 and 5.06 × 104 for Bba3263AUMC, Bba3076AUMC and Man3085AUMC, respectively, and their slopes were determined by computerized probit analysis program as 0.738 ± 0.008, 0.635 ± 0.007 and 1.120 ± 0.024, respectively.

Selective effect of the systemic insecticide Phosphamidon on soil, root-surface and leaf-surface fungi

Results of the effect of Phosphamidon on soil, root- and leaf-surface fungi of Vigna sinensis var. azmerly were generally inconsistent. However, there were some consistent ones. Its effect on soil, root- and leaf-surface fungi persisted till after 40 days. In soil the total count was regularly increased after 20 days by the low and medium doses and after 40 days by the high dose. In the rhizosphere, Fusarium was almost consistently activated by the three doses after 5 days of treatment and by the low dose after 20 days. In the rhizoplane, the total count of fungi was lowered by the three doses after 40 days in the two sowings. Alternaria alternata was toxicated by the three doses after several experimental periods of the two sowings in the phyllosphere and phylloplane. When this insecticide was incorporated with the agar medium, it was of no significant effect on the total count of fungi at the low and medium doses but abnormally increased the total count at the high dose. In the liquid medium, the mycelia of the test fungi were not significantly affected except that of Penicillium corylophilum which was significantly retarded by the three doses and Rhizopus stolonifer which was significantly activated by the high dose.

EFFECT OF THE HERBICIDE FLUAZIFOP-BUTYL ON FUNGAL POPULATIONS AND ACTIVITY IN SOIL

The side effects of fluazifop-butyl on soil fungal populations and oxygen uptake were studied by incubating soil samples with a range of fluazifop-butyl concentrations (0, 0.6, 3 and 6 μg g−1) over 8 weeks. Cellulose decomposition in soil was also studied in laboratory experiments with the herbicide which was either incorporated in soil or sprayed onto calico squares which were buried in soil. The mycelial dry weight of six fungal species under the effect of the herbicide was also examined. Fluazifop-butyl had no significant effect on total fungal propagule populations at 0.6 μg g−1. At 3 and 6 μg g−1, it caused temporary reduction in fungal populations observed after 1 and 2-wk of incubation. The herbicide had no significant effect on OZ uptake. The decay of calico buried in herbicide-treated soil was generally stimulated, while the decomposition of herbicide-treated calico, buried in untreated soil, was temporary delayed. The mycelial dry weight yields of Aspergillus favus (at 2 and 12 μg mL−1 of fluazifop-butyl) and Cunninghamella echinulata (at 12 μg mL−1) were significantly increased. At 24 μg mL−1 the mycelial dry weight of A. flavus and Alternaria alternata was significantly reduced.

Keratinolytic fungi of wadi Qena in Egypt

Forty-six soil samples collected from different sites of wadi Qena were examined for keratinophilic fungi using the hair baiting technique. Thirty-two species in addition to one variety of each ofA. nidulans andA. flavus which belong to eighteen genera were recovered.Aspergillus, Chrysosporium, Penicillium, Microsporum andFusarium were the most frequent genera developed from baited soils.

Effect of benomyl on soil, root-surface and leaf-surface fungi

Summary Benomyl was almost regularly toxic to the total count of soil and root- and leaf-surface fungi, and the toxicity persisted till the end of the experiment. Most of the fungi were also toxicated at certain periods and doses. Altemaria alternata could noticeably resist the effect of Benomyl at most of the treatments and at some treatments its count was promoted. When incorporated with the agar medium, the counts of most of the soil fungi were drastically reduced by the three doses. Altemaria alternata could also survive the fungicide at the higher doses, while Rhizopus stolonifer was the only fungus whose count was significantly raised at the medium dose. In the liquid medium all test fungi were almost significantly retarded or completely eliminated by the three doses, except Cladosporium cladosporioides which was not significantly affected by any dose.

Fungi in Two Swimming Pools in Assiut Town, Egypt

50 water samples from 2 public swimming pools were tested for the presence of fungi using the hair baiting technique and plate count methods. Sabourauds-dextrose agar and Littman-oxgall agar media were used for isolation of the fungi. Of the keratinolytic fungi 8 species were recorded of which three species were dermatophytes (Trichophyton terrestre, 14% of the samples; T. mentagrophytes, 10% and Microsporum gypseum, 6%). On Littman-oxgall agar the following species were recovered: Aspergillus flavus, A. fumigatus, A. niger, Penicillium chrysogeman, Syncephalastrum racemosum, Alternaria alternata and Mucor hiemalis.