Assessment of recent outbreaks of Dickeya sp (syn. Erwinia chrysanthemi) slow wilt in potato crops in Israel

Suspected Dickeya sp. strains were obtained from potato plants and tubers collected from commercial plots. The disease was observed on crops of various cultivars grown from seed tubers imported from the Netherlands during the spring seasons of 2004-2006, with disease incidence of 2-30% ( 10% in average). In addition to typical wilting symptoms on the foliage, in cases of severe infection, progeny tubers were rotten in the soil. Six strains were characterised by biochemical, serological and PCR amplification. All tests verified the strains as Dickeya sp. The repPCR and the biochemical assays showed that the strains isolated from blackleg diseased plants in Israel were very similar, if not identical to strains isolated from Dutch seed potatoes, suggesting that the infection in Israel originated from the Dutch seed. The strains were distantly related to D. dianthicola strains, typically found in potatoes in Western Europe, and were similar to biovar 3 D. dadanti or D. zeae. This is the first time that the presence of biovar 3 strains in potato in the Netherlands is described. One of the strains was used for pathogenicity assays on potato cvs Nicola and Mondial. Symptoms appeared 2 to 3 days after stem inoculation, and 7 to 10 days after soil inoculation. The control plants treated with water, or plants inoculated with Pectobacterium carotovorum, did not develop any symptoms with either method of inoculation. The identity of Dickeya sp. and P. carotovorum re- isolated from inoculated plants was confirmed by PCR and ELISA

PREPARATION PROCEDURES OF FUNGAL PHYTO-PATHOGENS SAMPLES FOR ANALYSIS BY MALDI-TOF AND FTIR MICROSCOPY

Reliable and rapid identification of phyto-pathogens causing plant diseases is playing an important role in their control strategies. The available methods for identification of fungi are time consuming and not always very specific. MALDI-TOF and Fourier-transform infrared (FTIR) microscopy are proved to be comprehensive and sensitive analytical methods for detection of molecular changes in cells. Due to the similarity between the obtained spectra of different species of fungal pathogens, it is important to choose the most appropriate procedure for the preparation of the examined samples. Such procedure might improve the discrimination between these species. In the present study, we compared between three possible procedures of pathogen sample preparation for their examination by MALDI-TOF and FTIR microscopy. Our results showed that preparation of the fungal sample directly from liquid growth media is considered as the best way of fungal sample preparation for both MALDI-TOF and FTIR microscopy examination

Estimating the delay between host infection and disease (incubation period) and assessing its significance to the epidemiology of plant diseases.

Knowledge of the incubation period of infectious diseases (time between host infection and expression of disease symptoms) is crucial to our epidemiological understanding and the design of appropriate prevention and control policies. Plant diseases cause substantial damage to agricultural and arboricultural systems, but there is still very little information about how the incubation period varies within host populations. In this paper, we focus on the incubation period of soilborne plant pathogens, which are difficult to detect as they spread and infect the hosts underground and above-ground symptoms occur considerably later. We conducted experiments on Rhizoctonia solani in sugar beet, as an example patho-system, and used modelling approaches to estimate the incubation period distribution and demonstrate the impact of differing estimations on our epidemiological understanding of plant diseases. We present measurements of the incubation period obtained in field conditions, fit alternative probability models to the data, and show that the incubation period distribution changes with host age. By simulating spatially-explicit epidemiological models with different incubation-period distributions, we study the conditions for a significant time lag between epidemics of cryptic infection and the associated epidemics of symptomatic disease. We examine the sensitivity of this lag to differing distributional assumptions about the incubation period (i.e. exponential versus Gamma). We demonstrate that accurate information about the incubation period distribution of a pathosystem can be critical in assessing the true scale of pathogen invasion behind early disease symptoms in the field; likewise, it can be central to model-based prediction of epidemic risk and evaluation of disease management strategies. Our results highlight that reliance on observation of disease symptoms can cause significant delay in detection of soil-borne pathogen epidemics and mislead practitioners and epidemiologists about the timing, extent, and viability of disease control measures for limiting economic loss.ML thanks the Institut Technique français de la Betterave industrielle (ITB) for funding this project. CAG and JANF were funded by the UK’s Biotechnology and Biological Sciences Research Council (BBSRC). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript

First report of potato blackleg caused by a biovar 3 Dickeya sp. in Georgia

In Western and Northern Europe, Dickeya species are causing increasingly severe economic losses in potato (Solanum tuberosum) crops. The costs of seed potato production resulting from Dickeya spp. infection are high due to rejection and declassification of seed tubers (Slawiak et al., 2009). Potato blackleg caused by Dickeya spp. is primarily a seed tuber-borne disease (Tsror et al., 2009). Symptoms including blackening of the stem base, wilting of plants and rotten seed tubers are observed. Recently, outbreaks of potato blackleg were recorded in Georgia on three cultivars, in Samtskhe-Javakheti region, Akhalkalaki district, in an area in excess of 100 hectare

FTIR spectroscopy for detection and identification of fungal phytopathogenes

Abstract. Soil-borne fungi are considered as major pathogens to many plants and can cause a severe economic damage. Early detection and identification of these pathogens is very important and might be critical for their control. The available methods for identification of fungi like molecular biology, serological tests and PCRs tests (polymerase chain reaction) are time consuming and not always very specific. Fourier-transform infrared (FTIR) attenuated total reflection (ATR) spectroscopy, is considered to be a comprehensive and sensitive method for detection of molecular changes in intact cells. In the present study we used FTIR-ATR as a sensitive and effective assay for the detection and discrimination between different fungal genera. Our results showed significant spectral differences between the various examined fungi genera. These results proved the possibility of discrimination between these fungi on the genus level