Experimental infection of pheasants with Lednice (Yaba 1) virus.

Young pheasants (24-hour- and 7-day-old) are capable of producing viraemia and antibodies after experimental infection with Lednice virus even after low doses of virus (0.7-0.9 log mouse LD50/g). Viraemia lasts approximately 3 days, but the titres of virus in the blood are low. The possible role of young pheasants in the circulation of virus in nature is discussed.     

Effects of Ampropylfos (RS)-1-aminopropylphosphonic acid) on zoospore formation,repeated zoospore emergence and oospore formation in Aphanomyces spp.

The effects on growth, asexual and sexual reproduction of different Aphanomyces species by the new fungicide ampropylfos ((RS)-1-aminopropylphosphonic acid) were tested using highly synchronized cultures. Ampropylfos reduced mycelial growth in Aphanomyces astaci, A. euteiches and A. stellatus. The fungicide was found to reduce zoospore numbers in all Aphanomyces species tested except A. euteiches. In one species, A. stellatus, zoospore production was inhibited at much lower fungicide concentrations than in the other species tested. In the pea pathogen A. euteiches, ampropylfos reduced the number of oospores, whereas the fungicide had little effect on asexual reproduction.     

Effect of T-activin on the course of experimental infection with Taenia crassiceps (Zeder, 1800) in mice

T-activin--an immunomodulating preparation of polypeptidic character prepared from calf thymus--was used for influencing the course of infection in a model system mouse-Taenia crassiceps. A single s.c. application of 100 micrograms of T-activin at various intervals before and after infection resulted in a marked decrease in the number of cysticerci in peritoneal cavities of experimental mice (by 47.1-93.6%) compared to the controls. After s.c. application of T-activin and i.p. injection of antigen (crude T. crassiceps larvae homogenate from mice) the decrease in the cystricercus number was still more pronounced than in the mouse groups receiving only T-activin or homogenate (by 76.9% in comparison with 65.5% and 17.0%, respectively). A combination of T-activin with crude T. crassiceps homogenate from rats did not produce the same effect in experimental mice. The protective effect of individual combinations of T-activin with the homogenate does not correlate with the antibody level in the serum of infected mice.     

Studies on infection of bean (Phaseolus vulgaris) and soybean (Glycine max) by ascospores of Sclerotinia sclerotiarum

Factors influencing the infection of bean and soybean by ascospores of Sderotinia sclerotiorum were studied. In the absence of an exogenous nutrient source, ascospores on intact host tissues produced a short and usually sub-polar germ-tube but only young host tissues were penetrated by the infection hypha arising from the germinated spore. There was a hypersensitive response by cells to penetration and generally the fungus remained restricted to these cells, though it continued to grow within them. Water-soaked lesions characteristic of successful infections only developed when many individual infection sites coalesced following inoculation with high concentrations of ascospores. Flowers or parts of flowers provided a suitable nutrient base for initial colonization from ascospore inoculum. Mycelium extending from this base initiated infection of intact host surfaces. Pollen stimulated growth from germinating ascospores in vitro and in vivo but did not stimulate infection of bean.     

Experimental infection of the squirrel (Sciurus vulgaris) and the muskrat (Ondatra zibethica) with Tahyna virus (California group, Bunyaviridae)

Two squirrels aged 16 weeks and three muskrats aged 24 weeks were subcutaneously infected with a dose of 400 SMicLD50 of the extraneurally passaged "236" strain of Tahyna virus. Viremia was detected in one squirrel (48 and 96 hours post infection) and in two muskrats (24 and 48 hours p.i.). Seroconversion was demonstrated by plaque-reduction neutralization test (PRNT) 21 days p.i. in all animals.     

Influence of thymic preparations on the result of experimental infection with Taenia crassiceps (Zeder, 1800) in ICR mice

Thymalin (Thymarin) and T-activin--thymic preparations of polypeptidic character--were used for influencing the parasitic infection in a model system mouse--Taenia crassiceps. A single subcutaneous application of 100 micrograms of Thymalin per mouse at the day of infection resulted in a decrease (by 54.9%) in the number of cysticerci in peritoneal cavity of experimental mice compared with the controls. Administration of Thymalin with T. crassiceps larval homogenate at various intervals before and after infection resulted in a statistically significant increase of the level of specific antibodies in the serum of infected mice, this increase, however, did not correlate with the corresponding protective effect. Immunosuppressant azathioprine, injected subcutaneously from 7th to 3rd day preceding infection at a dose of 100 micrograms resulted in a significant increase in the number of T. crassiceps larvae in the peritoneal cavity of experimental mice compared with the controls (by 48.7%). T-activin, injected subcutaneously to mice, immunosuppressed by azathioprine, led to a restoration of resistance of mice to T. crassiceps infection. Subcutaneous application of T-activin alone had a significant protective effect (decrease in cysticerci number by 53.7% in comparison with the controls). Correlation of the level of specific antibodies in the serum of infected mice, value of spleen index and number of T. crassiceps cysticerci in peritoneal cavity of mice was not detected.     

Studies on resistance to beet western yellows virus in lettuce (Lactuca sativa) and the occurrence of field sources of the virus

An effective method based on glasshouse and field procedures was developed for screening commercial cultivars and other lettuce types for resistance to beet western yellows virus (BWYV). Field experiments in 1985, 1986 and 1987 showed that lettuce cultivars varied in their reaction to BWYV, but no high levels of resistance were identified in the main commercial types. Crisp types generally showed milder symptoms than butterhead or cos types, but individual butterhead cultivars were identified with resistance equal to the best crisp types. The highest levels of resistance were identified in Batavian type cultivars and extreme resistance or possible immunity was found in Lactuca perennis and L. muralis . BWYV caused yield reductions in some cultivars as high as 63% and reduced maturation by up to 38%, in others. There was no correlation between chlorotic leaf symptom severity and yield reduction.
BWYV was isolated from a range of weed and non-lettuce host species growing near affected lettuce crops. Isolates of BWYV obtained from infected lettuce and brassicas appeared to be similar. They infected sugar beet with difficulty but caused no symptoms, and could only be detected by ELISA serology.     

Studies on BHC isomers and related compounds V. Some physicochemical properties of BHC isomers (1)

Physicochemical properties of biological interest were measured for hexachlorocyclohexane (benzene hexachloride) isomers, including solubility in water and in aqueous protein solutions, partition coefficients between organic solvents and water, and some “adsorption equilibrium” constants between the macromolecules and water. Some of the properties show a correlation with the free energy-related hydrophobic parameter “π”.     

Studies on Botrytis spp. occurring on onions (Allium cepa) and leeks (Allium porrum)

Botrytis byssoidea (mycelial neck rot) was more prevalent than B. allii (sclerotial neck rot) on the leaves of field onions and the bulbs of stored onions grown in some of the areas where onions or onions and leeks had previously been grown sequentially.
B. byssoidea and B. porri were also isolated from leeks. Spores of B. allii, B. byssoidea (from onions and leeks), B. porri , and B. squamosa caused infection of seedlings of salad (green) and bulb onions.
Inoculation with B. squamosa spores caused severe infection of seedling leaves, but inoculation with mycelial discs caused little damage to onion bulb tissue. By comparison, mycelial discs of the remaining species were highly pathogenic to bulbs.
The practical implications of disease transfer of certain of these species between onions and leeks are discussed.     

Survey of granulosis virus infection in sugarcane borers,Chilo infuscatellus Snellen and C. sacchariphagus indicus (Kapur) in India

Abstract

A survey was undertaken to observe the pevalence of granulosis viruses infecting sugarcane shoot borer Chilo infuscatellus Snellen and internode borer C. sacchariphagus indicus (Kapur) in Tamil Nadu State and Union Territory of Pondicherry in India. Nine districts in Tamil Nadu and Pondicherry had the occurrence of shoot borer granulosis virus in all the locations surveyed ranging from 2.6 to 14.6%. In internode borerthe mortality varied from 3.8 to 31.5% in the eight districts of Tamil Nadu and Pondicherry.     

Studies in the growth of Pteridium aquilinum (L.) Kuhn. (bracken) 1. Regeneration of rhizome segments

The patterns of regeneration of Pteridium aquilinum (L.) Kuhn. (bracken) rhizome segments grown in pot culture are described. The overall capacity for regeneration was unaffected by the rhizome type planted, i.e., whether it consisted of only a length of frond-bearing ‘short shoote’ or whether this was attached to part of the main storage and exploratory ‘long shoot’. In all cases rhizomes extended, produced new lateral buds and developed fronds during the first summer. Regenerative capacity was also similar for segments with or without apical buds. Different patterns of growth were observed in plants grown from different types of segment: in particular, more new lateral buds were produced on rhizome segments originally lacking an apex. As rhizomes extended, the distance between successive lateral buds increased. The results are discussed in relation to the possible roles of correlative inhibition and patterns of translocation between fronds and rhizomes and to information on field populations.     

The effects of co‐infection by different Potato virus Y (PVY) isolates on virus concentration in solanaceous hosts and efficiency of transmission

The influence of co‐infection on concentration and accumulation of genetically different isolates of Potato virus Y (PVY) in potato and tobacco plants and the efficiency of transmission by Myzus persicae of PVY isolates from doubly versus singly infected plants were evaluated. The vector ability to simultaneously transmit two virus isolates was examined. Eight PVY isolates represented three strain groups: PVY^O (pathotype and serotype O), PVY^NW (pathotype N and serotype O), and PVY^NTN (pathotype and serotype N). Different diagnostic methods, including DAS‐ELISA, multiplex RT‐PCR, aphid transmission tests and bioassays, were applied to detect the presence of PVY isolates in source and assay plants. Significant reductions in concentrations of certain PVY isolates during co‐infection with other isolates were found both in potato and tobacco plants. The observed effects were both isolate‐ and host‐dependent in form. The highest rates of virus transmission by single aphids were recorded with PVY^NTN isolates, and the lowest ones with PVY^O isolates. Individual aphids of M. persicae were able to simultaneously transmit two PVY isolates. The frequency of transmission was generally low, but it reached as high as 20% for one of the isolate combinations. The findings presented in the work provide proof for antagonistic within‐plant interactions between isolates of PVY, with some implications of these interactions for virus transmission by aphid vectors. Consequently, this research contributes to a better understanding of the epidemiology of the disease caused by PVY.     

Indian peanut clump virus (IPCV) infection on wheat and barley: symptoms, yield loss and transmission through seed

Wheat and barley crops were shown to be susceptible to Indian peanut clump virus (IPCV) under field conditions. In wheat, the Hyderabad isolate of IPCV (IPCV-H) induced symptoms resembling the rosette caused by soil-borne wheat mosaic virus, and these were apparent only three weeks after emergence. Early-infected plants were severely stunted and dark green, with chlorotic streaks on the youngest leaves, which turned necrotic as the plants aged; most of these plants died. Late-infected plants were also stunted and were conspicuous in the field because of their dark green appearance as a result of delayed maturity. The virus was detected by ELISA and nucleic acid hybridization in all plants with symptoms. These plants usually produced fewer tillers than healthy ones. Spikes were malformed, often did not emerge from the flag leaf, and they contained few, shrivelled seeds. Grain yield was decreased, on average, by 58%. In barley, IPCV-H caused severe stunting and general leaf chlorosis. As the plants aged, the leaves became necrotic and the few infected plants that reached maturity produced small spikes. IPCV-H antigens were detected by ELISA in every wheat seed from infected plants and the virus was transmitted through wheat seed at a frequency of 0.5–1.3%. Storage at 4°C for more than a year did not affect seed transmission frequency. The virus was detected in leaves and roots of seed-transmitted plants. Seed transmission was not detected in barley. The Durgapura isolate (IPCV-D) was detected in wheat crops (cv. RR-21) at 3 different locations in Rajasthan State, India. Infected plants showed reduced growth without any overt symptoms.     

Effect of κ/ß-Carrageenan from red alga Tichocarpus crinitus (Tichocarpaceae) on infection of detached tobacco leaves with tobacco mosaic virus

Journal of Plant Diseases and Protection - It is shown that κ/ß-carrageenan obtained from red marine alga Tichocarpus crinitus possesses antiviral activity against Tobacco mosaic virus...     

Studies on the biology of black mould (Aspergillus niger) on temperate and tropical onions. 1. A comparison of sources of the disease in temperate and tropical field crops

Aspergillus niger colonies were present on 60–90% of the leaves sampled from onion crops grown under hot, tropical conditions (Shambat, Sudan), but only on 21% of leaves in crops grown under temperate conditions (Wellesbourne, UK). The seed stocks used in the Sudan were naturally contaminated with A. niger , whereas the fungus was absent from seed used in the UK. Inoculation of seed with A. niger resulted in an increase in the incidence of the fungus on onion plants (mean 83% of plants with affected leaves) in the field and on bulbs in store in crops grown in the UK. In the UK, A. niger is infrequent in the soil and air, but it is a major component of the soil and air mycoflora in the Sudan. Most of the bulbs grown in Sudan were contaminated with A. niger at harvest because of the high incidence of the fungus in the field.     

用模糊综合评判法探讨桔小实蝇在中国的适生分布

笔者以桔小实蝇（Ｂａｃｔｒｏｃｅｒａｄｏｒｓａｌｉｓ）为研究对象,依据其生物生态学特性,选择了７项生态因子,以中国２９个有代表性的站点,１０年的气象资料（１９８６～１９９６）,应用模糊综合评判的数学方法,探讨了该虫在中国的适生分布范围。结果表明,北纬２５°以南的地区为桔小实蝇的最适宜分布区,四川盆地和贵州的部分地区是桔小实蝇的适宜分布区,北纬２５°以北、长江以南的地区是次适生分布区,其余地区是非适宜分布区。     

Review of the sequential development of Loma salmonae (Microsporidia) based on experimental infections of rainbow trout (Oncorhynchus mykiss) and Chinook salmon (O. tshawytscha)

Loma salmonae is a common gill parasite of salmonids, and essentially all species in the genus Oncorhynchus are susceptible. Infections occur in both fresh and salt water. Loma salmonae is directly transmissible by ingestion of spores or infected tissue. The parasite infects the wall of blood vessels of various organs, but the gill is the primary site of infection. Initial infection occurs in the intestine, and xenomas are easily detected in the gills by standard histology at 4-6 wk post-exposure. A few presporogonic stages of the parasite are found in the heart endothelium prior to xenoma formation in the gills. Ultrastructure studies of early infections demonstrated that wandering blood cells transport the meronts to the gills, and that merogony occurs in pillar cells and other cells underlying the gill endothelium. Xenomas develop in these cells, resulting in hypertrophied host cells filled with spores. Xenomas ultimately rupture, and are associated with severe inflammation in which free spores are found in macrophages. The parasites are most pathogenic during this phase of the infection, resulting in severe vasculitis and clinical disease. Both rainbow trout (Oncorhynchus mykiss) and Chinook salmon (Oncorhynchus ishawytscha) recover from infections, but free spores persist in kidney and spleen phagocytes for many months after xenomas are absent in Chinook salmon. Fish that have recovered from the infection show strong immunity against the parasite, lasting up to 1 year. Fish are susceptible to infection by other routes of exposure by spores; co-habitation, anal gavage, and intramuscular, intraperitoneal and intravascular injection. Autoinfection probably occurs following release of spores in blood vessels after xenomas rupture. The optimal temperature for L. salmonae infections is 15-17 degrees C, with a permissive range of 11-20 degrees C.