Time filter

Source Type

Sharabani G.,Israel Agricultural Research Organization | Sharabani G.,The Hebrew University | Manulis-Sasson S.,Israel Agricultural Research Organization | Chalupowicz L.,Israel Agricultural Research Organization | And 7 more authors.
Plant Pathology | Year: 2014

Clavibacter michiganensis subsp. michiganensis (Cmm), the causal agent of bacterial canker and wilt, causes severe economic losses in tomato net-houses and greenhouses worldwide. In this study, seedlings which were transplanted and inoculated monthly over 2 years wilted and died earlier in the spring (21-24°C) and autumn (18-23°C) than in the winter (15-18°C) and summer (28-31°C): T50 (the time taken for 50% of the plants to wilt or die) was 2 and 3-4 months after inoculation, respectively. A highly significant correlation was found between the average temperatures during the first month after inoculation and T50; the shortest T50 mortality (70 days) was observed for an average temperature of 26°C. Expression of virulence genes (pat-1, celA, chpC and ppaA) by Cmm was higher in plants inoculated in the spring than in those inoculated in the summer. In another set of experiments, seedlings were inoculated and maintained in controlled-environment growth chambers for 2 weeks. Subsequently, they were transplanted and maintained in commercialtype greenhouses for 4-5 months. The temperatures prevailing in the first 48 h after inoculation were found to affect Cmm population size and virulence gene expression and to have season-long effects on bacterial canker development. © 2014 British Society for Plant Pathology.


Blank L.,Israel Agricultural Research Organization | Cohen Y.,Israel Agricultural Research Organization | Borenstein M.,Israel Agricultural Research Organization | Shulhani R.,Israel Agricultural Research Organization | And 4 more authors.
Phytopathology | Year: 2016

Clavibacter michiganensis subsp. michiganensis, the causal agent of bacterial canker and wilt of tomato, is considered to be one of the most important bacterial pathogens worldwide. In the year 2000 there was an increase in the number of infected greenhouses and in the severity of the disease in Israel. As part of the effort to cope with the disease, a comprehensive survey was conducted. Scouts recorded disease severity monthly in 681 production units. At the end of the season the scouts met with the growers and together recorded relevant details about the crop and cultural practices employed. The results suggested an absence of anisotropy pattern in the study region. Global Moran's I analysis showed that disease severity had significant spatial autocorrelation. The strongest spatial autocorrelation occurred within a 1,500 m neighborhood, which is comparable to the distance between production units maintained by one grower (Farm). Next, we tested three groups of variables including or excluding the Farm as a variable. When the Farm was included the explained variation increased in all the studied models. Overall, results of this study demonstrate that the most influential factor on bacterial canker severity was the Farm. This variable probably encompasses variation in experience, differences in agricultural practices between growers, and the quality of implementation of management practices. © 2016 The American Phytopathological Society.


Sharabani G.,Israel Agricultural Research Organization | Shtienberg D.,Israel Agricultural Research Organization | Borenstein M.,Israel Agricultural Research Organization | Shulhani R.,Israel Agricultural Research Organization | And 5 more authors.
Plant Pathology | Year: 2013

The effect of plant age at the time of inoculation on the severity of bacterial wilt and canker disease caused by Clavibacter michiganensis subsp. michiganensis (Cmm) was examined in six greenhouse experiments. The period during which inoculations led to wilt and death of tomato plants was defined. This period, designated 'window of vulnerability', ranged from transplanting to the 17- to 18-leaf stage. Plants inoculated after this period expressed disease symptoms but did not wilt or die. No significant changes in disease incidence were observed when leaves of different ages were inoculated. Yield accumulation was significantly reduced in plants inoculated within the window of vulnerability compared with those inoculated after this period. Expression of virulence genes, viz. celA, encoding a secreted cellulase, and the serine protease-encoding pat-1, chpC and ppaA, was induced during the early stages after inoculation in plants inoculated within the window of vulnerability. Differences in Cmm population between plants inoculated within and outside of this period were insignificant after the first week post-inoculation, indicating that differences in disease severity, yield loss and expression of virulence determinants are not correlated with Cmm population level. Results suggest that implementation of precautionary measures during the window of vulnerability to avoid secondary spread of Cmm will have a season-long effect on plant mortality and may minimize, or even prevent, yield losses. © 2012 British Society for Plant Pathology.


Sharabani G.,Israel Agricultural Research Organization | Manulis-Sasson S.,Israel Agricultural Research Organization | Borenstein M.,Israel Agricultural Research Organization | Shulhani R.,Israel Agricultural Research Organization | And 3 more authors.
Plant Pathology | Year: 2013

Bacterial canker, caused by Clavibacter michiganensis subsp. michiganensis (Cmm), can spread in commercial tomato greenhouses causing epidemics. Results of greenhouse experiments with Cmm-contaminated tools demonstrated disease spread for only a limited distance (<4 plants) from infected plants. However, touching symptomless infected plants bearing guttation droplets prior to touching nearby plants spread the pathogen over longer distances within rows (>22 plants). The pathogen was exuded in large numbers in the guttation fluid of infected plants; its presence in the guttation fluid was not influenced by the inoculation procedures, leaf age or the volume of the guttation droplets. Population size of Cmm and the incidence of leaflets with epiphytic bacteria were significantly higher in plants placed in a guttation-induction chamber than in those kept in a growth chamber with high humidity, suggesting exudation through guttation contributed to the formation of epiphytic populations on leaflets. This new knowledge may provide a simple and environmentally friendly means for decreasing the spread of the disease by avoiding contact with plants during periods when they bear guttation droplets. © 2012 BSPP.


Shtienberg D.,Israel Agricultural Research Organization | Sharabani G.,Israel Agricultural Research Organization | Bornstein M.,Israel Agricultural Research Organization | Shulhani R.,Israel Agricultural Research Organization | And 4 more authors.
Acta Horticulturae | Year: 2015

Severe epidemics of bacterial canker and wilt disease (caused by Clavibacter michiganensis subsp. michiganensis; Cmm) occurred in Israel between the years 2005 to 2007, resulting in substantial yield loss in many greenhouses. As there were no effective means to cope with the disease, a national research project named 'Khosen Clavibacter' ('Khosen' in Hebrew is an acronym for 'Green Agriculture and Clean Environment'), in which all aspects of disease development were studied, was initiated. It was found that the main source of initial inoculum in commercial greenhouses was asymptomatic seedlings provided by the nurseries. The primary source of inoculum in the nurseries was infested seeds. Means to decrease the secondary spread of the pathogen from the primary infected seedling to the adjacent, healthy seedling in the nursery, were developed. In the commercial greenhouses the disease spread spatially during routine production procedures employed by the farm workers. Cmm-contaminated tools spread the disease for only a limited distance (<4 plants) from infected plants. However, touching asymptomatic infected plants bearing guttation droplets prior to touching nearby plants spread the pathogen over longer distances within rows (>22 plants). Experiments to study the effect of plant age at the time of inoculation on disease development revealed that the period during which inoculations led to wilt and death of tomato plants (designated "window of vulnerability") ranged from plants bearing 3-4 leaves (transplanting) to those with 17-18 leaves. Plants inoculated after this period expressed less severe disease symptoms and did not wilt or die. These results suggested that implementation of precautionary measures to avoid touching tomato plants bearing guttation droplets during the window of vulnerability would have a season-long effect on plant mortality and minimize, or even prevent, yield losses. This information was distributed to tomato growers in southern Israel. From August 2010 tomato growers received SMS messages twice a week informing them of the likelihood that weather conditions in the coming days would be conducive to guttation formation. Data collected in commercial greenhouses revealed that implementing the new recommendations resulted in a significant decrease in the occurrence of severe bacterial canker epidemics.

Loading Negev R and nter collaborators
Loading Negev R and nter collaborators