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.

scholarly journals Control of Downy Mildew in Greenhouse-Grown Cucumbers Using Blue Photoselective Polyethylene Sheets

Plant Disease ◽  
1997 ◽  
Vol 81 (9) ◽  
pp. 999-1004 ◽  
Author(s):  
Reuven Reuveni ◽  
Michael Raviv
Keyword(s):  
Downy Mildew ◽  
Field Experiments ◽  
Disease Incidence ◽  
Significant Inhibition ◽  
Blue Pigment ◽  
Pseudoperonospora Cubensis ◽  
Uv Spectrum ◽  
Four Seasons ◽  
Growth Chambers ◽  
Commercial Sheet

Six types of polyethylene sheets with or without a blue pigment, having an absorption peak at the yellow part of the spectrum (580 nm), in combination with three levels of UV-B (280 to 320 nm) absorbance, were investigated for their effects on sporangial production and colonization of Pseudoperonospora cubensis on cucumbers in growth chambers. The effect of these photoselective sheets on the epidemiology of downy mildew in greenhouse-grown cucumbers has been investigated in several locations. The addition of the blue pigment to the films resulted in a significant inhibition of colonization and sporangial production of P. cubensis, whereas filtration of the UV spectrum enhanced the colonization but had no effect on the sporangial production. The appearance of the first symptom-bearing plants was delayed under the blue covers, and consequently, a significant reduction in the disease incidence of downy mildew was recorded under all blue sheets at each corresponding level of UV-B transmittance in five different field experiments through four seasons. Regardless of the differences in disease incidence, there were no significant differences among the yields that were obtained under the various sheets, probably due to the lower photosynthetically active radiation transmissivity of the blue films. The optimal features required for a desirable commercial sheet are discussed.

scholarly journals CRISPR Is an Optimal Target for the Design of Specific PCR Assays for Salmonella enterica Serotypes Typhi and Paratyphi A

2014 ◽  
Vol 8 (1) ◽  
pp. e2671 ◽  
Author(s):  
Laetitia Fabre ◽  
Simon Le Hello ◽  
Chrystelle Roux ◽  
Sylvie Issenhuth-Jeanjean ◽  
François-Xavier Weill
Keyword(s):  
Salmonella Enterica ◽  
Specific Pcr ◽  
Optimal Target ◽  
Pcr Assays

scholarly journals Vegetation responses to season of fire in an aseasonal, fire-prone fynbos shrubland

PeerJ ◽  
2017 ◽  
Vol 5 ◽  
pp. e3591 ◽  
Author(s):  
Tineke Kraaij ◽  
Richard M. Cowling ◽  
Brian W. van Wilgen ◽  
Diba R. Rikhotso ◽  
Mark Difford
Keyword(s):  
Floristic Composition ◽  
Fire Season ◽  
Summer Drought ◽  
Winter Rainfall ◽  
Recruitment Success ◽  
Floral Diversity ◽  
Four Seasons ◽  
Different Seasons ◽  
Varied Response ◽  
One Year

Season of fire has marked effects on floristic composition in fire-prone Mediterranean-climate shrublands. In these winter-rainfall systems, summer-autumn fires lead to optimal recruitment of overstorey proteoid shrubs (non-sprouting, slow-maturing, serotinous Proteaceae) which are important to the conservation of floral diversity. We explored whether fire season has similar effects on early establishment of five proteoid species in the eastern coastal part of the Cape Floral Kingdom (South Africa) where rainfall occurs year-round and where weather conducive to fire and the actual incidence of fire are largely aseasonal. We surveyed recruitment success (ratio of post-fire recruits to pre-fire parents) of proteoids after fires in different seasons. We also planted proteoid seeds into exclosures, designed to prevent predation by small mammals and birds, in cleared (intended to simulate fire) fynbos shrublands at different sites in each of four seasons and monitored their germination and survival to one year post-planting (hereafter termed ‘recruitment’). Factors (in decreasing order of importance) affecting recruitment success in the post-fire surveys were species, pre-fire parent density, post-fire age of the vegetation at the time of assessment, and fire season, whereas rainfall (for six months post-fire) and fire return interval (>7 years) had little effect. In the seed-planting experiment, germination occurred during the cooler months and mostly within two months of planting, except for summer-plantings, which took 2–3 months longer to germinate. Although recruitment success differed significantly among planting seasons, sites and species, significant interactions occurred among the experimental factors. In both the post-fire surveys and seed planting experiment, recruitment success in relation to fire- or planting season varied greatly within and among species and sites. Results of these two datasets were furthermore inconsistent, suggesting that proteoid recruitment responses are not related to the season of fire. Germination appeared less rainfall-dependent than in winter-rainfall shrublands, suggesting that summer drought-avoiding dormancy is limited and has less influence on variation in recruitment success among fire seasons. The varied response of proteoid recruitment to fire season (or its simulation) implies that burning does not have to be restricted to particular seasons in eastern coastal fynbos, affording more flexibility for fire management than in shrublands associated with winter rainfall.

scholarly journals Trends in One-Year Recurrent Ischemic Stroke among the Elderly in the USA: 1994–2002

2010 ◽  
Vol 30 (5) ◽  
pp. 525-532 ◽  
Author(s):  
Norrina B. Allen ◽  
Theodore R. Holford ◽  
Michael B. Bracken ◽  
Larry B. Goldstein ◽  
George Howard ◽  
...  
Keyword(s):  
Ischemic Stroke ◽  
The Elderly ◽  
The Usa ◽  
One Year

Specific PCR and real-time PCR assays for detection and quantitation of ‘Candidatus Phytoplasma phoenicium’

2015 ◽  
Vol 29 (1) ◽  
pp. 63-70 ◽  
Author(s):  
Maan Jawhari ◽  
Peter Abrahamian ◽  
Ali Abdel Sater ◽  
Hana Sobh ◽  
Patil Tawidian ◽  
...  
Keyword(s):  
Real Time ◽  
Real Time Pcr ◽  
Specific Pcr ◽  
Pcr Assays

Headache

2002 ◽  
Vol 12 (2) ◽  
pp. 127-144
Author(s):  
GJF Saldanha ◽  
CG Clough ◽  
N Ward
Keyword(s):  
General Population ◽  
Elderly Population ◽  
Large Population ◽  
The Elderly ◽  
Epidemiological Studies ◽  
Population Based ◽  
Medical Attention ◽  
Population Based Study ◽  
The Usa ◽  
One Year

Little is known about the frequency of headache in the elderly population as few epidemiological studies have been carried out. In one year in the USA, 70% of the general population had a headache, 5% of whom sought medical attention. In a large population-based study carried out in East Boston, US, some 17% of patients over 65 yrs of age reported frequent headache, with 53% of women and 36% of men reporting headache in the previous year.

Sign in / Sign up

Export Citation Format

Share Document