Mammalian cell cultures affected by Naegleria gruberi

Amebae of 8 strains of Naegleria gruberi were able to destroy 10 established mammalian cell lines including lung, kidney, ovary, connective tissue, neuroblastoma, and laryngeal and cervical carcinoma cells. The strains of N. gruberi varied in their ability to produce a destructive effect (DE) in African green monkey kidney (Vero) cell cultures. However, cell line susceptibility was found to be equivalent when tested with the considerably destructive 1518/l strain of N. gruberi. The Vero cell line proved to be a useful indicator culture for assessing the destructive potential of N. gruberi strains. Other factors affecting the extent of DE produced were ameba to mammalian cell ratio and the length of time that amebae were maintained in cell culture.     

Sources, survival and transmission of Cladosporium allii and C. allii-cepae, leaf blotch pathogens of leek and onion

Neither Cladosporium allii nor C . allii-cepae was detected in seed samples of 46 commercial cultivars of leek and nine of onion.
In glasshouse tests where flower inflorescences of onions and leeks were dusted with conidia of C. alliicepae and C. allii , respectively, few onion seeds and no leek seeds became contaminated. In field crops of leeks some spathes and inflorescences became diseased and gave 0 002% C. allii contaminated seeds. No infected onion seeds were obtained from naturally-infected plants in the field.
Conidia of both fungi survived for less than 6 weeks in sterile and non-sterile soil (during which time the temperature varied from -8 to +11 C); pseudothecial bodies survived longer.
Both pathogens survived for 3 months in debris of onion or leek on the surface of soil in pots under similar conditions. In debris buried at a depth of 7 cm in sterile or unsterile soil they survived for 2 months. Although C. allii survived only 1 month in debris on the soil surfaces following a leek crop, conidia of the fungus were trapped from the air above the area for at least 6 months and healthy leeks transplanted into this area developed the disease. No leaf blotch developed in leeks grown on land which had not previously borne that crop.     

Normal germling development by Erysiphe graminis on cereal leaves freed of epicuticular wax

Experiments were conducted to test the hypothesis that recognition of the physical structure of epicuticular leaf waxes by Erysiphe graminis may be important to the development of normal germlings and the formation of functional appressoria. Comparisons of germination rates and characteristics of germling development by E. graminis f.sp. avenae , and in one experiment by f.sp. hordei , were made between intact cereal leaves and leaves from which the epicuticular waxes had been stripped away.
Overall, fungal development was very similar on intact and wax-free leaves: although germination rates were slightly, but significantly, lower, and lengths of appressorial germ tubes slightly greater, on stripped than intact leaves, a very similar proportion of germlings formed apparently normal appressoria in both cases. This was true for f.sp. avenae on first- and fifth-formed leaves of susceptible and adult plant resistant oats, and on barley and wheat first leaves, and for f.sp. hordei on first leaves of barley, oat and wheat. The appressoria formed on stripped leaves not only appeared normal, but also formed haustoria with at least the same frequency as on intact leaves; in several experiments, a higher proportion formed haustoria in stripped than intact leaves. Wax removal did not affect the adult plant resistance of oat cv. Maldwyn, which limits haustorium formation by appressoria, indicating that epicuticular wax was not involved in this resistance. It is concluded that the physical structure of epicuticular wax is not involved in the recognition processes leading to normal germling development.     

A new genus of capillariids from birds, Ornithocapillaria gen. n. (Nematoda: Capillariidae)

A new genus, Ornithocapillaria gen. n., belonging to the family Capillariidae and subfamily Baruscapillariinae is described and its diagnosis is given. The type species of the genus is Ornithocapillaria ovopunctata (Linstow, 1873) comb. n., other species are O. cylindrica (Eberth, 1863) comb. n., O. quiscali (Read, 1949) comb. n., and O. picorum (Rudolphi, 1819) comb. n. The new genus is characterized by a relatively large membranous pseudobursa, shape of processes supporting pseudobursa, and presence of a vulval appendage in female. It includes only species parasitic in the intestine of birds of the orders Passeriformes, Falconiformes, Strigiformes, and Piciformes.     

Tobacco rattle virus serotypes and associated nematode vector species of Trichodoridae in the bulb-growing areas in the Netherlands

Soil samples from the coastal bulb-growing areas in the provinces of North- and South-Holland and the North-East Polder in the Netherlands were examined for trichodorid nematodes and tobacco rattle virus (TRV) serotypes. At least one of a total of eight species of Trichodoridae, of whichParatrichodorus pachydermus was most prevalent, was found in 93% of the samples from the provinces of North- and South-Holland and TRV, including four serotypes, was obtained from 49% of these samples. In the North-East Polder one of three species of trichodorids, of whichP. teres occurred most frequently, was present in 72% of the samples, and TRV of one serotype was obtained from 28% of these samples. The TRV isolates recovered from these samples reacted serologically with one of four antisera to strains of TRV. Virus transmitted byP. pachydermus reacted to the PRN-, byTrichodorus viruliferus to the RQ-, byP. teres to the N5- and byT. similis, to the TS-antiserum, respectively.     

Growth of the mycoparasitic fungus Verticillium biguttatum from different geographical origins at near-minimum temperatures

Sclerotia ofRhizoctonia solani collected from potato tubers from different countries were assayed for the presence of mycoparasites. Among the mycoparasites observedVerticillium biguttatum predominated. Its geographical distribution was not restricted to certain latitudes or soil types;V. biguttatum occurred worldwide in potato fields.The minimum growth temperature of 57V. biguttatum isolates was found to be in the narrow range from 10 to 13°C, irrespective of their geographical origin. A non-linear logistic growth model was used to describe the radial growth onRhizoctonia mycelium and nutrient agar plates. At near-minimum temperature the maximum colony radii varied considerably; they were up to 3.8 times that of the reference isolate M73. Based on parameter values for logistic growth, fast-and slow-growing isolates could be distinguished. Although the growth properties ofV. biguttatum isolates from different locations varied, the presence of fast- and slow-growing isolates was not restricted to particular areas and both types could be found in the same field. However, bioassays with selected fast- and slow-growing isolates do not support the assumption that growth at near-minimum temperatures is a relevant criterion for screening isolates ofV. biguttatum in terms of effectiveness for biological control ofR. solani.     

Microspalacinae, a new subfamily of the feather mite family Alloptidae Gaud (Acarina, Analgoidea).

Microspalacinae subfam. n. (Analgoidea, Alloptidae) is established for the feather mite genus Microspalax Mégnin et Trouessart (= Connivelobus Dubinin, new synonymy). Morphologies of the species are described and illustrated with line drawings and SEM micrographs, and taxonomical comments are given for named species. The mites are known from shearwaters (Procellaridae) and stormpetrels (Hydrobatidae); host associations are discussed. The alloptid subfamily Thysanocercinae Atyeo et Peterson is elevated to familial rank.     

Studies on the development of the cestode Proteocephalus neglectus La Rue, 1911 (Cestoda: Proteocephalidae) under experimental conditions

A part of the life cycle of Proteocephalus neglectus La Rue, 1911, a parasite of trout, starting from release of eggs from mature parasites into water, to the early phase of development in the definitive host, was studied under experimental conditions. Special regard has been paid to development in the intermediate host, copepod Cyclops strenuus. Some oncospheres in eggs kept in water at 5 and 10 degrees C remained infective for 20-25 days. The percentage of infected copepods depended on the length of their contact with parasite eggs. Cestode larvae (cercoscoleces) were formed in the intermediate host on days 8-10 p.i. at the temperatures of 21-22 degrees C, on days 18-21 at 15 degrees C, on days 24-28 at 10 degrees C, and on days 59-65 at 6 degrees C. Most larvae, including infective cercoscoleces, were localized in the cephalothorax of the intermediate host, particularly in its first segment. This localization did not change during their development. The infectivity of cercoscoleces was verified by experimental infection of Salmo gairdneri fry. The development of the cestode in this definitive host was observed for 17 days after infection at 10 degrees C. The finding of P. neglectus cereoscoleces in fish of the families Cottidae and Cyprinidae on day 2 after experimental infection indicates that these larvae can survive for a short time in atypical fish hosts.     

A comparison of methods to evaluate the susceptibility of potato cultivars to blackleg (caused by Erwinia carotovora subsp. atroseptica) in the field at different sites

Potato seed tubers were inoculated either using a needle or using a high-pressure jet injector at a number of sites in the United Kingdom. Over 2 years, different cultivars showed different trends in blackleg symptoms. Comparisons with inoculation by infiltration of tubers under vacuum were made at two sites, and by damaging followed by dipping tubers in inoculum at one site. The relationship between plant vigour in July and yield was closer than that between blackleg symptoms and yield.     

Powdery mildews on borage (Borago officinalis) and evening primrose (Oenothera biennis)

The powdery mildews Erysiphe cynoglossi and E. howeana, causing disease on borage (Borago officinalis) and evening primrose (Oenothera biennis), respectively, are reported for the first time in Britain.