Predicting the potential global distribution of <i>Pseudomonas syringae</i> pv <i>actinidiae</i> (Psa)

The increasing spread of kiwifruit bacterial canker caused by Pseudomonas syringae pv actinidiae (Psa) prompted a modelling effort to assess the global and local potential risk of this species The current potential distribution of Psa was modelled with two wellused models (CLIMEX and MaxEnt) based on available presence records and environmental data Most discrepancies in model projections occurred for New Zealand data that was used for validation Model projections can provide information to alert decisionmakers in kiwifruitgrowing regions to prepare for possible incursions of Psa However in this study because model findings did not agree on the New Zealand validation data more research is necessary to achieve greater confidence on projections for novel areas Despite that result this study provides useful information for some kiwifruit growing countries that have not yet been affected by Psa such as USA Iran Greece Belgium Denmark and especially South Africa where commercial kiwifruit orchards have been planted recentl

BLIGHTSIM: A new potato late blight model simulating the response of Phytophthora infestans to diurnal temperature and humidity fluctuations in relation to climate change

Temperature response curves under diurnal oscillating temperatures differ from those under constant conditions for all stages of the Phytophthora infestans infection cycle on potatoes. We developed a mechanistic model (BLIGHTSIM) with an hourly time step to simulate late blight under fluctuating environmental conditions and predict late blight epidemics in potato fields. BLIGHTSIM is a modified susceptible (S), latent (L), infectious (I) and removed (R) compartmental model with hourly temperature and relative humidity as driving variables. The model was calibrated with growth chamber data covering one infection cycle and validated with field data from Ecuador. The model provided a good fit to all data sets evaluated. There was a significant interaction between average temperature and amplitude in their effects on the area under the disease progress curve (AUDPC) as predicted from growth chamber data on a single infection cycle. BLIGHTSIM can be incorporated in a potato growth model to study effects of diurnal temperature range on late blight impact under climate change scenarios

Potential global and regional geographic distribution of Phomopsis vaccinii on Vaccinium species projected by two species distribution models

Vaccinium twig blight (caused by Phomopsis vaccinii, teleomorph Diaporthe vaccinii) is a major endemic disease on blueberries and cranberries in the Eastern and Northwestern USA and Canada. It has also been found in Europe, Chile and China. Publications on its occurrence in the USA and Canada indicate that the pathogen is limited to cool climates. Published data on worldwide occurrence were inventoried and supplemented with National Plant Diagnostic Network (NPDN) data in the USA. These occurrence and long-term climate data were entered in the niche models MaxEnt and Multi-Model Framework to predict the potential global distribution of the disease. Precipitation in the driest quarter and mean annual temperature contributed most to the prediction. The results indicate that P. vaccinii is not limited to cool climates, although the optimal annual average temperature is 10 °C according to the MaxEnt model. The models correctly predicted that the climate in the central and eastern USA and the west coast of the USA and Canada would be conducive to blueberry twig blight. Large areas in Europe, eastern Australia and New Zealand, and smaller areas in South America and East Asia would be conducive too. For the first time, the NPDN database was shown to be an important source of information for the prediction of the potential global distribution of a plant pathogen