Studies on the mycoflora of Aswan High Dam Lake, Egypt: monthly variations.

Fifty-one species and one variety appertaining to twenty one genera of mesophilic fungi were recovered from the monthly samples of marginal water (44 species, 1 variety and 18 genera) and submerged mud (78 species, 1 variety and 30 genera) of Aswan High Dam Lake during the period from July 1985 to December 1986. The most common species were Aspergillus fumigatus, A. flavus, A. terreus, A. niger and Penicillium funiculosum. The highest fungal populations were almost detected either in October, in December 1985 or in February 1986. Of the 12 thermophilic and thermotolerant fungal species, A. fumigatus and A. nidulans were the most common. Paecilomyces variotii, Rhizomucor pusillus, Thermomyces lanuginosus, Thermoascus thermophilus and Sporotrichum thermophilum were fairly common in one locality or more. The physico-chemical characteristics of water and mud samples were also followed.

Studies on the mycoflora of Aswan High Dam Lake, Egypt: vertical fluctuations.

The fungal population of Aswan High Dam Lake showed marked vertical variations during the period of study which extended from July 1985 to December 1986. High fungal counts were observed at the surface water which were mainly due to the high counts of Aspergillus fumigatus and A. terreus. Going deeper the fungal population decreased till 30 meters, then gradually increased to reach its maximum at the 70 meter depth (near the bottom of the lake). Such increase was basically due to the high population of Penicillium funiculosum. At each sampling time, the water temperature and the values of dissolved oxygen were always higher at the surface than near the bottom of the lake. The temperature ranged from 15 degrees to 26 degrees C and the dissolved oxygen from 1.31 to 8.98 mg 1(-1).

Aquatic fungi associated with seven species of Nile fishes (Egypt).

Ten identified species in addition to 2 unidentified species of Achlya and Pythium which belong to seven zoosporic fungal genera (aquatic freshwater fungi) were recovered during this investigation. The fish species with most zoosporic fungi (5 species and 3 genera) was Tilapia nilotica. The fish species with least fungi were Bagrus bayad and Syndontis schall (yielded only one species each). Mormyrus kannum did not give any zoosporic fungal species. Some aquatic fungi emerged only from internal organs of some fish species. 46 species belonging to 22 terrestrial fungal genera were also recovered during this work. The broadest spectrum (15 species) was recorded in the second external wash water (WE2) of Mormyrus kannum and the narrowest spectrum (2 species) in the second internal wash water (WI2) of Schilbe mystus and with the scales of Labeo niloticus. First wash water of internal organs (WI1) of Tilapia nilotica yielded the highest total count (6.95% of total count) and the second wash water of internal organs (WI2) of Schilbe mystus yielded the lowest total count (0.34% of total count). Nile water sample (NW) yielded 3.67% of total fungi and eight species which belong to seven genera. Aspergillus was the most common (31 out of 31 samples) and yielded 52.40% of total fungi. It was represented by 12 species and one variety of A. flavus var. columnaris (broadest spectrum). Penicillium was represented by 7 species and found in 19 out of 31 samples yielding 11.02% of total fungi.

Seasonal fluctuations of freshwater fungi in river Nile (Egypt).

The seasonal fluctuations of aquatic fungi were studied over 24 water sample collected monthly between May 1979 and April 1981 from the River Nile near Assiut (about 375 km, south from Cairo, Egypt). The richest periods in aquatic fungal genera and species were September--December 1979, January--March, October--December 1980, and January--April 1981. These periods represent low or moderate temperature months. The poorest periods were May--August 1979, April, May, July, August and September 1980 which are almost summer months. Twenty-nine species and one variety of Olpidiopsis saprolegniae which belong to ten genera of aquatic fungi were collected during this investigation. Three genera were of high seasonal occurrence (19-24 months) namely: Achlya, Saprolegnia and Dictyuchus. Three other genera were of moderate seasonal occurrence (6-11 months) namely: Isoachlya, Leptolegnia and Pythium. The rest of genera were of low or rare seasonal occurrence.

Effect of five pesticides on the mycelial growth of some soil and pathogenic fungi.

The effect of three doses (the lowest is the recommended dose in the field) of 5 pesticides namely: Ceresan, Orthocid (fungicides), VCS-438 (herbicide), and Dursban and Dipterex (insecticides) on the mycelial dry weight of Aspergillus fumigatus. Fusarium moniforme, Pencillium italicum, and Sclerotium ceprivorum was tested 2, 4, 6, 8 and 10 days after treatment. All the pesticides induced inhibition of mycelial growth of the test fungi. Only VCS-438 at the low dose was stimulatory to F. moniliforme after 4 and 6 days and to P. italicum after 4 days. The rate of inhibition was influenced by the type of fungus, the age of the mycelium, and the dose of the pesticide. At the end of the experiment the two fungicides were detoxified by the test fungi with a rate higher than that of the other pesticides.

Rhizosphere fungi of five plants in Egypt.

75 species which belong to 25 genera were collected during this investigation. All of these fungi were previously isolated from Egyptian soils and other sources. The total count and the number of genera and species in the rhizosphere soil of the 5 plants were regularly higher than in non-rhizosphere soil. The composition of the rhizosphere fungus flora was considerably influenced by the type and the age of the plant. The most prevalent fungi in the rhizosphere of the test plants after 45, 90, and 150 days were as follows: in Helianthus annuus, Stachybotrys atra and Aspergillus niger; in Chrysanthemum coronarium, Cladosporium herbarum, A. sydowii and Penicillium funiculosum; in Nigella sativa, Fusarium moniliforme and A. sydowii; in Datura innoxia, A. fumigatus and A. terreus; in Hyoscyamus muticus, C. herbarum and A. sydowii; and in soil, P. funiculosum, A. terreus and A. niger. The counts of total fungi and most of the common fungal species, except in the case of Datura innoxia, reached their maxima after 90 days and sharply declined after 150 days.