Preliminary study of seed transmission of downy mildew in some vegetable brassica cultivars in Australia

1997 ◽  
Vol 26 (1) ◽  
pp. 54 ◽  
Author(s):  
P.A. Smith ◽  
T.V. Price
Keyword(s):  
Downy Mildew ◽  
Seed Transmission ◽  
Preliminary Study ◽  
Vegetable Brassica

Seed transmission of maize downy mildew (Peronosclerospora sorghi) in Nigeria

2000 ◽  
Vol 49 (5) ◽  
pp. 628-634 ◽  
Author(s):  
V. O. Adenle ◽  
K. F. Cardwell
Keyword(s):  
Downy Mildew ◽  
Seed Transmission ◽  
Peronosclerospora Sorghi

Peronospora trifoliorum. [Descriptions of Fungi and Bacteria].

1983 ◽  
Author(s):  
S. M. Francis
Keyword(s):  
Medicago Sativa ◽  
Downy Mildew ◽  
Geographical Distribution ◽  
Systemic Infection ◽  
Seed Transmission ◽  
Field Conditions ◽  
Infected Leaf ◽  
Light Green

Abstract A description is provided for Peronospora trifoliorum. Information is included on the disease caused by the organism, its transmission, geographical distribution, and hosts. HOSTS: Medicago sativa subsp. saliva, M. sativa subsp. falcata. DISEASE: Downy mildew of lucerne (alfalfa). Infected leaflets, which tend to be near the top of the stem, are light green or yellow. The affected areas can vary from small localized spots to larger areas of infected leaf or a systemic infection where the entire shoot may become yellow, stunted and swollen. GEOGRAPHICAL DISTRIBUTION: Worldwide, wherever lucerne is grown. CMI Map No. 343 includes records on clover and other hosts. TRANSMISSION: Mycelium is reported to overwinter in the crown bud (42, 617). Conidia are produced the following spring and in damp and humid conditions soon spread the disease. Oospores occur but reports on their frequency under field conditions are so few that it is difficult to assess their importance in overwintering the disease. Seed transmission, though suspected by Eriksson (1930) and also reported from Italy in a sample of seed from Argentina (Campbell, 1922), is thought to be unimportant (Richardson, 1979).

Seed Transmission of Spinach Downy Mildew

Plant Disease ◽  
1983 ◽  
Vol 67 (10) ◽  
pp. 1139 ◽  
Author(s):  
T. Inaba
Keyword(s):  
Downy Mildew ◽  
Seed Transmission ◽  
Spinach Downy Mildew

scholarly journals Investigation of Seed transmission in Peronospora belbahrii the Causal Agent of Basil Downy Mildew

Agronomy ◽  
2019 ◽  
Vol 9 (4) ◽  
pp. 205 ◽  
Author(s):  
Lidan Falach-Block ◽  
Yariv Ben-Naim ◽  
Yigal Cohen
Keyword(s):  
Downy Mildew ◽  
Latent Infection ◽  
Seed Transmission ◽  
Economic Damage ◽  
Specific Pcr ◽  
Four Seasons ◽  
The Usa ◽  
Growth Chambers ◽  
Pcr Assays ◽  
One Year

Downy mildew in sweet basil (Ocimum basilicum L.) caused by the oomycete pathogen Peronospora belbahrii Thines was first recorded in Israel in 2011. Within one year, the pathogen has spread all over the country, causing devastating economic damage to basil crops. Similar outbreaks were reported in Europe, the USA, and Asia. Seed transmission and seedling trade were suggested as possible explanations for this rapid spread. Here, we show that P. belbahrii can develop systemically in artificially inoculated basil plants in growth chambers. It may reach remote un-inoculated parts of the plant including the axillary buds but not the roots or seeds. To verify whether transmission of the disease occurs via seeds, we harvested seeds from severely infected, field-grown basil plants. Harvests were done in four seasons, from several basil cultivars growing in three locations in Israel. Microscopic examinations revealed external contamination with sporangia of P. belbahrii of untreated seeds, but not of surface-sterilized seeds. Pathogen-specific PCR assays confirmed the occurrence of the pathogen in untreated seeds, but not in surface-sterilized seeds. Contaminated seeds were grown (without disinfection) in pasteurized soil in growth chambers until the four–six leaf stage. None of several thousand plants showed any symptom or sporulation of downy mildew. PCR assays conducted with several hundred plants grown from contaminated seeds proved no latent infection in plants developed from such seeds. The results confirmed that (i) P. belbahrii can spread systemically in basil plants, but does not reach their roots or seeds; (ii) sporangia of P. belbahrii may contaminate the surface, but not the internal parts, of seeds produced by infected basil plants in the field: and (iii) contaminated seeds produce healthy plants, which carry no latent infection. The data suggest that P. belbahrii in Israel is seed-borne, but not seed-transmitted.

Peronospora antirrhini. [Descriptions of Fungi and Bacteria].

1981 ◽  
Author(s):  
S. M. Francis
Keyword(s):  
Downy Mildew ◽  
Geographical Distribution ◽  
Seed Transmission ◽  
Lower Surface ◽  
Flowering Plants ◽  
Antirrhinum Majus ◽  
High Humidity ◽  
Secondary Infections ◽  
Leaf Surfaces ◽  
Definite Proof

Abstract A description is provided for Peronospora antirrhini. Information is included on the disease caused by the organism, its transmission, geographical distribution, and hosts. HOSTS: Antirrhinum majus, A. nuttallianum, Misopates orontium. DISEASE: Downy mildew of antirrhinum. This is mainly a disease of seedlings and young plants. The infection is systemic and affected plants appear stunted and pale yellowish-green. The leaves are curled inwards and droop down. Conidiophores develop on the lower surface forming a fine white to purple down. In heavy infections the down is found on both leaf surfaces and also on the stems. The growing point may be killed and then plants often break from the base and produce several new shoots. Conidia can cause secondary infections on the leaves of older plants especially in conditions of high humidity. These appear as pale yellowish spots. GEOGRAPHICAL DISTRIBUTION: Worldwide, see CMI Map No. 222 ed. 2, 1971. TRANSMISSION: Seed transmission by oospores was tentatively suggested by Yarwood (1947). Moore & Moore (1952) refer to circumstantial evidence but say there is no definite proof. Peronospora antirrhini is not recorded as a seed pathogen by Richardson (1979) but Neergaard (1977) points out that for seed-borne infection of a downy mildew to be effective all that is needed is a mere trace of the fungus on the seed. As Yarwood (1947) indicates, terminal infections of flowering plants could easily contaminate seed.

scholarly journals PRELIMINARY STUDY ON THE HETEROTIC PATTERN OF TROPICAL QUALITY PROTEIN MAIZE (QPM) AND DOWNY MILDEW RESISTANCE (DMR) MAIZE INBREDS

Zuriat ◽  
2015 ◽  
Vol 16 (2) ◽  
Author(s):  
D. Ruswandi
Keyword(s):  
Small Group ◽  
Downy Mildew ◽  
Major Group ◽  
Annual Rainfall ◽  
Quality Protein Maize ◽  
Downy Mildew Resistance ◽  
Heterotic Groups ◽  
Mildew Resistance ◽  
Preliminary Study ◽  
Maize Inbreds

Exploration of heterotic patterns among maize inbreds has become important since it could provide information on which new germplasm could be used to improve base population in breeding program. This experiment was a preliminary study on the heterotic relationships between tropical quality protein maize (QPM) and downy mildew resistance (DMR) maize inbreds based on analysis on combining ability. Seven tropical maize inbreds were crossed in a line × tester. One commercial hybrid from Bisi Company, Bisi 2, was included for the evaluation of hybrids as check cultivar. The result revealed that two heterotic groups has been recognized, i.e., major group consisted of CML 161, CML 163, CML 172, Nei 9008, and P345. Whereas the small group contains MR 10 and Ki 3. The hybrids and their parental inbreds were evaluated in Jatinangor, Indonesia (753 m above sea level) in 2003 to 2004. The location of yield test has a humid climate with an annual rainfall of about 1925 mm. The field experiment was arranged in a randomize block design with two replications. The present study revealed two heterotic groups: major group involving CML 161, CML 163, CML 172, Nei 9008, and Ki 3; and small group containing MR 10 and P 345. Moreover, the major group can be divided into two subgroups involving all CML lines for the first subgroup and Nei 9008 and Ki 3 for the second subgroup.

scholarly journals Epidemiology of Basil Downy Mildew

2017 ◽  
Vol 107 (10) ◽  
pp. 1149-1160 ◽  
Author(s):  
Yigal Cohen ◽  
Yariv Ben Naim ◽  
Lidan Falach ◽  
Avia E. Rubin
Keyword(s):  
Downy Mildew ◽  
Leaf Surface ◽  
Continuous Light ◽  
Infection Intensity ◽  
Seed Transmission ◽  
The United States ◽  
Spore Formation ◽  
Sweet Basil ◽  
Wide Range ◽  
Highly Effective

Basil downy mildew (BDM) caused by the oomycete Peronospora belbahrii is a destructive disease of sweet basil (Ocimum basilicum) worldwide. It originated in Uganda in the 1930s and recently spread to Europe, the Middle East, Americas, and the Far East. Seed transmission may be responsible for its quick global spread. The pathogen attacks leaf blades, producing chlorotic lesions with ample dark asexual spores on the lower leaf surface. Oospores may form in the mesophyll of infected leaves. The asexual spores germinate on a wet leaf surface within 2 h and penetrate into the epidermis within 4 h. Spore germination and infection occur at a wide range of temperatures from 5 to 28.5°C. Infection intensity depends on the length of dew period, leaf temperature, and inoculum dose. The duration of latent period (from infection to sporulation) extends from 5 to 10 days, depending on temperature and light regime. The shortest is 5 days at 25°C under continuous light. Sporulation requires high humidity but not free leaf wetness. Sporulation occurs at 10 to 26°C. At the optimum temperature of 18°C, the process of sporulation requires 7.5 h at relative humidity ≥ 85%, with 3 h for sporophores emergence from stomata and 4.5 h for spore formation. Sporophores can emerge under light or darkness, but spore formation occurs in the dark only. Limited data are available on spore dispersal. Spores dispersed from sporulating plants contaminate healthy plants within 2 h of exposure. Settled spores may survive on leaf surface of healthy plants for prolonged periods, depending on temperature. Seed transmission of the disease occurs in Europe, but not in Israel or the United States. P. belbahrii in Israel also attacks species belonging to Rosemarinus, Nepeta, Agastache, Micromeria, and Salvia but not Plectranthus (coleus). A Peronospora species that infects coleus does not infect sweet basil. Control of BDM includes chemical, physical, and genetic means. The fungicide mefenoxam was highly effective in controlling the disease but resistant populations were quickly selected for in Israel and Europe rendering it ineffective. A new compound oxathiapiprolin (OSBP inhibitor) is highly effective. Nocturnal illumination of basil crops controls the disease by preventing sporulation. Daytime solar heating suppressed the disease effectively by reducing spore and mycelium viability. The most effective physical means is fanning. Nocturnal fanning prevents or limits dew deposition on leaf surfaces, and as a result, infection and sporulation diminish and epidemics are prevented. Genetic resistance occurs in wild basil and its transfer to sweet basil is under way.

The Ultrastructure of Metastatic Human Mammary Carcinoma After Prolonged Estrogen Therapy

1967 ◽  
Vol 25 ◽  
pp. 180-181
Author(s):  
John H.L. Watson ◽  
John L. Swedo ◽  
R.W. Talley
Keyword(s):  
Mammary Carcinoma ◽  
Osmium Tetroxide ◽  
Estrogen Therapy ◽  
Ultrastructural Level ◽  
Uranyl Acetate ◽  
Human Mammary Carcinoma ◽  
Surgical Biopsy ◽  
Lead Hydroxide ◽  
Preliminary Study ◽  
Hormonal Therapies

A preliminary study of human mammary carcinoma on the ultrastructural level is reported for a metastatic, subcutaneous nodule, obtained as a surgical biopsy. The patient's tumor had responded favorably to a series of hormonal therapies, including androgens, estrogens, progestins, and corticoids for recurring nodules over eight years. The pertinent nodule was removed from the region of the gluteal maximus, two weeks following stilbestrol therapy. It was about 1.5 cms in diameter, and was located within the dermis. Pieces from it were fixed immediately in cold fixatives: phosphate buffered osmium tetroxide, glutaraldehyde, and paraformaldehyde. Embedment in each case was in Vestopal W. Contrasting was done with combinations of uranyl acetate and lead hydroxide.

Fine structure of early degenerating myofibers in the tibialis anterior of young ‘MDX’ mouse

1988 ◽  
Vol 46 ◽  
pp. 322-323
Author(s):  
H.D. Geissinger ◽  
C.K. McDonald-Taylor
Keyword(s):  
Fine Structure ◽  
Muscle Regeneration ◽  
Tibialis Anterior ◽  
Genetic Defect ◽  
Mdx Mouse ◽  
Mdx Mice ◽  
Histopathological Changes ◽  
Electron Microscopic ◽  
Dystrophic Mouse ◽  
Preliminary Study

A new strain of mice, which had arisen by mutation from a dystrophic mouse colony was designated ‘mdx’, because the genetic defect, which manifests itself in brief periods of muscle destruction followed by episodes of muscle regeneration appears to be X-linked. Further studies of histopathological changes in muscle from ‘mdx’ mice at the light microscopic or electron microscopic levels have been published, but only one preliminary study has been on the tibialis anterior (TA) of ‘mdx’ mice less than four weeks old. Lesions in the ‘mdx’ mice vary between different muscles, and centronucleation of fibers in all muscles studied so far appears to be especially prominent in older mice. Lesions in young ‘mdx’ mice have not been studied extensively, and the results appear to be at variance with one another. The degenerative and regenerative aspects of the lesions in the TA of 23 to 26-day-old ‘mdx’ mice appear to vary quantitatively.

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