Tolypocladium terricola sp. N., a new mosquito-killing species of the genus Tolypocladium Gams (Hyphomycetes).

A new entomopathogenic species of the genus Tolypocladium, T. terricola is described from a soil sample from Finalnd. From other known Tolypocladium species, T. terricola differs in morphology, production of secondary metabolites and possession of relatively strong mosquitocidal activity. The fungus is characterized by broad oval conidia (2.5 x 2 microns) with one pointed end which are produced in grape-like clusters, and are not firmly adherent. When treated with T. terricola, mosquito larvae show typical features of intoxication characterized by the concentration of larvae in the centre of cup, hanging by their siphons on the surface.     

The life cycle of Rubenstrema opisthovitellinum So?tys, 1954 (Trematoda: Omphalometridae).

The life cycle of Rubenstrema opisthovitellinum So?tys, 1954, a parasite of shrews, is elucidated. The following developmental stages are described in detail: daughter sporocyst, cercaria, metacercaria, and adult. The freshwater snail Planorbarius corneus was found to be the first intermediate host in nature. The metacercariae were obtained from the larvae of mosquitoes Culex molestus and only exceptionally from snails Physa acuta. The adults were obtained from the small intestine of hamsters Mesocricetus auratus. The life cycle and the larval stages of R. opisthovitellinum are described for the first time.     

Intestinal parasites: a study of human appendices

Histological sections of 414 appendices were examined parasitologically. Enterobius vermicularis was found in 8.7%, eggs of Ascaris lumbricoides in 0.5%, trophozites of Dientamoeba fragilis in 4.8%, Endolimax nana in 2.2%, Entamoeba coli in 1% and cysts of Giardia intestinalis in 1.9% of cases. Appendicopathies associated with Enterobius were most frequent in the age group from 6 to 10 years (24.3%) and from 21 to 25 years (12.2%). Patients older than 15 years were practically women only. Dientamoeba was most frequent in the age group from 11 to 15 years (11.3%). In women D. fragilis was three times more frequent than in men. The coincidence of D. fragilis and E. vermicularis infections was 50%. No interactions were seen between the protozoans in the contents of the appendix and its mucous membrane. Statistical evaluation indicates possible etiologic role of E. vermicularis in the occurrence of acute appendicities. D. fragilis appears to be the most common intestinal protozoan parasite in Bohemia.     

The relationship between antifungal diene levels and fungal inhibition during quiescent infection of unripe avocado fruits by Colletotrichum gloeosporioides

Quantitative changes in the antifungal compound, 1-acetoxy-2-hydroxy-4-oxo-heneicosa-12.15-diene, in freshly harvested avocado fruits during the initial stages of fungal development were investigated to determine the possible involvement of the compound in quiescent infections of Colletotrichum gloeosporioides. The concentration of the antifungal compound in the peel decreased to subfungitoxic concentrations 16 h after harvest. Fifty-six hours later the antifungal diene had increased to c . 3800 μg/g fresh weight. At this stage, germinated appressoria had penetrated the cuticle to the epidermal cells but no fungal development was observed until 7 days later when the concentration of the diene had decreased to 100-110μg/g fresh weight. Following a dip treatment at 55°C for 5 or 10 min, the antifungal diene concentration decreased as in the controls, but it remained at subfungitoxic concentrations for a longer period enabling fungal development and early symptom expression.
The concentration of the diene in the flesh of freshly harvested fruit decreased to 120 μg/g fresh weight 24 h after harvest. Inoculation of peeled fruits with spores of C. gloeosporioides showed germination without appressoria formation and symptom expression occurred 24-48 h later. Symptom expression was delayed if fruits were inoculated after coating the flesh with epicuticular wax extracts or if the flesh was inoculated 3 days after harvest when the antifungal diene had regained a fungitoxic concentration. Disease symptoms were expressed in soft fruits containing subfungitoxic concentrations of the diene.
We conclude that the diene in unripe avocado fruits inhibits fungal development of germinated appressoria or conidia. The quiescent structure of C. gloeosporioides in unripe avocado fruit is a subcuticular hypha.     

Characterization of an isolate of beet mosaic virus from South Kazakhstan

A filamentous virus isolated from a sugar-beet plant showing systemic mosaic collected in South Kazakhstan was identified as an isolate of beet mosaic virus (BMV-K). BMV-K was transmitted by the green peach aphid Myzus persicae in a non-persistent manner, and by sap inoculation to 11 out of 19 species from seven families tested. The virus could not be transmitted to Nicotiana tabacum, N. debneyi, N. glutinosa and N. clevelandii, cither mechanically or with M. persicae. The thermal inactivation point of BMV-K in sugar-beet sap was 55-60 C, dilution end point 1:1000 and longevity in vitro 2 days at 20 C. A purification procedure produced 1-5-3 mg of purified virus from 100 g of infected Stellaria media plants. Purified virus contained a single protein species of molecular weight 34 700 Da. In ELISA tests, BMV-K reacted positively with BMV-specifc antisera obtained from Japan. Germany and Portugal. By competitive DAS- ELISA, the virus isolate was shown to be closely serologically related to all the three isolates of BMV, and very distantly related to bean yellow mosaic and soy bean mosaic viruses.     

Selection of sorghum (Sorghum bicolor (L.) Moench) varieties resistant to the parasitic weed Striga hermonthica (Del.) Benth

Pot and field experiments were performed in Burkina Faso in 1987 and 1988 to evaluate the resistance of selected ‘low-stimulant’ sorghum (Sorghum bicolor (L.) Moench) varieties to the parasitic weed (Striga hermonthica (Del.) Benth. In a pot experiment, the variety IS-7777 supported the lowest number and had the latest emergence of Striga, compared with the other varieties tested. The varieties IS-14825, IS-6961, IS-7739, IS-14928 and IS-14975 also had signifi cantly lower numbers of emerged Striga per pot than the resistant control Framida. The resist ance of IS-7777 was confirmed in field experi ments, as was that of IS-7739, IS-6961 and IS-14928. However, the yield potential of these poorly adapted varieties was low in Striga-infested fields. The varieties IS-14975, IS–14825 and Seguetana Niarabougou exhibited a low susceptibility associated with a grain yield equivalent to that of the other varieties in farm fields infested by Striga. As Seguetana is already grown by Sahelian farmers, its use could be recommended in the absence of resistant varieties adapted to Sahelian agroclimatic conditions. The exceptionally high level of restance exhibited by IS-7777 could be exploited in studies on the genetics and mechanisms of resistance of the host plant to the parasite, as well as in sorghum improvement programmes.     

Comparative purification methods for determination of triadimenol residues in plant material

Two procedures are described for the determination of residues of triadimenol and compared on cereal material. After extraction, purification is carried out by Florisil column chromatography in method I and by semi-preparative High-Performance Liquid Chromatography in method II. Triadimenol residues are quantified by gas chromatography with a thermoionic detector. With method I, interference was observed but not with method II. This specific procedure has been tested on other plant materials. Recoveries in the range of 90–98% indicate that this procedure is suitable for residue analysis of this fungicide with detection limits of 0·008 mg kg^?1 in wheat grains, 0·03 mg kg^?1 in wheat straw and 0·004–0·008 mg kg^?1 in other plants. Maximum residue limits in France are: 0·1 mg kg^?1 in grain, 2·0 mg kg^?1 in straw and 1·0 mg kg^?1 in other vegetables and fruit.