Environmental and inoculum effects on epidemiology of bacterial spot disease of stone fruits and development of a disease forecasting system
Bacterial spot disease of stone fruits, caused by Xanthomonas arboricola pv. pruni, is of high economic importance in the major stone-fruit-producing areas worldwide. A better understanding of disease epidemiology can be valuable in developing disease management strategies. The effects of weather variables (temperature and wet/dry period) on epiphytic growth of X. arboricola pv. pruni on Prunus leaves were analyzed, and the relationship between inoculum density and temperature on disease development was determined and modeled. The information generated in this study, performed under controlled environmental conditions, will be useful to develop a forecasting system for X. arboricola pv. pruni. Optimal temperature for growth of epiphytic populations ranged from 20 to 30 °C under leaf wetness. In contrast, multiplication of epiphytic populations was not only interrupted under low relative humidity (RH) (< 40%) at 25 °C, but also resulted in cell inactivation, with only 0.001% initial cells recovered after 72 h incubation. A significant effect of inoculum density on disease severity was observed and 106 CFU/ml was determined as the minimal infective dose for X. arboricola pv. pruni on Prunus. Infections occurred at temperatures from 15 to 35 °C, but incubation at 25 and 30 °C gave the shortest incubation periods (7.7 and 5.9 days respectively). A model for predicting disease symptom development was generated and successfully evaluated, based on the relationship between disease severity and the accumulated heat expressed in cumulative degree day (CDD). Incubation periods of 150, 175 and 280 CDD were required for 5, 10 and 50% of disease severity, respectively.
KeywordsEpiphytic growth Incubation period Inoculum potential Growth rate Leaf wetness Temperature
We are grateful to Agromillora Catalana for supplying plant material (GF677 plants). We thank Marc Nicolàs and Josep Pereda for helpful collaboration, and Shirley Burgess for assistance in language editing.
This research was supported, in part, by grants from the Ministerio de Educación, Ciencia y Deporte (AGL2013–41405-R) of Spain, from the University of Girona (SING12/13 and MPCUdG2016/085) and from the European Union’s Seventh Framework Programme for research, technological development and demonstration under grant agreement number 613678 (DROPSA). Gerard Morales was the recipient of predocotoral fellowships from the University of Girona (BR 2013/31) and from MECD (FPU13/04123) from Spain.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
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