Bacterial blight of soybean caused by Pseudomonas glycinea is endemic in North America. It has also been reported in South European crops. Furthermore, the causal agent is a quarantine organism which means that its introduction into Europe is prohibited. However, yield losses and quality damages due to this bacterium have never been assessed in Europe. Moreover, the disease epidemiology under European climatic conditions is not known.
The project aims to bring some answers to these questions.
Bacterial blight of soybean caused by Pseudomonas syringae pv glycinea is endemic in North America and has also been reported in southern Europe. Loses in terms of yield and quality owing to this bacterium have never been assesed in Europe and its epidemiology under European climatic conditions is unknown. Work is being done to assess losses in both yield and quality caused by this disease.
Field experiments are being carried out in 3 locations, namely, Angers (France), Bologna (Italy) and Sevilla (Spain). In each experiment, 1, 2 or 3 varieties of soybean are used and with each variety, 2 seed infection levels are compared with a healthy check. The seeds were artificially infected with a selected strain of Pseudomonas syringae pv glycinea by gently pricking seedcoats and dipping the seeds into a suspension of the pathogen. The seeds were sown immediately after infection. During the growing season, field plots have been observed weekly for the presence and development of bacterial blight and the incidence and severity of the disease has been assessed. Epiphytic populations of Pseudomonas syringae pv glycinea have also been assessed at 2 stages of growth when the plant showed 2 true leaves and at the beginning of the blooming period. Records were kept of climatic conditions throughout the growing season. Harvested seeds were submitted to analysis in order to evaluate their levels of contamination.
The main study shall deal with yield losses and quality damages caused by this disease. The comparison of the grains harvested in experimental plots sown with either healthy or infected at different levels seeds should allow to determine a threshold above which the organism causes damages. Observations made during the growing season shall allow to precise some aspects of the development of the disease under European conditions. A sanitary standard for soybean seeds might be then suggested, and a manual on the detection of the disease in the crops will be published.
The study includes four soybean varieties in three experimental places. Three infection levels will be compared to a healthy check.
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