The potential global climate suitability of Kiwifruit bacterial canker disease (Pseudomonas syringae pv. actinidiae (Psa)) using three modelling approaches: CLIMEX, Maxent and Multimodel Framework

In recent years, outbreaks of kiwifruit bacterial canker (Pseudomonas syringae pv. actinidiae, Psa) have caused huge economic losses to two major global kiwifruit producers, Italy and New Zealand. To evaluate the potential global risk areas of Psa, three modelling methods (MaxEnt, CLIMEX and a Multi-Model Framework, including Support Vector Machine or SVM) were used. Current global occurrence data for Psa were collected from different sources. The long-term climate data were sourced from WorldClim and CliMond websites. The model results were combined into a consensus model to identify the hotspots. The consensus model highlighted the areas where two or three models agreed on climate suitability for Psa. All three models agreed with respect to the climate suitability of areas where Psa is currently present and identified novel areas where Psa has not established yet. The SVM model predicted large areas in Central Asia, Australia, and Europe as more highly suitable compared to MaxEnt and CLIMEX. Annual mean temperature and annual precipitation contributed most to the MaxEnt prediction. Both MaxEnt and CLIMEX showed the probability of Psa establishment increased above 5 °C and decreased above 20 °C. The annual precipitation response curve showed that excessive rain (>1200 mm/y) constrains Psa establishment. Our modelling results will provide useful information for Psa management by highlighting the climatically susceptible areas where Psa has not established, such as the USA, Iran, Denmark, Belgium and especially South Africa, where kiwifruit has been planted commercially in recent years

Global climate suitability of citrus huanglongbing and its vector, the Asian citrus psyllid, using two correlative species distribution modeling approaches, with emphasis on the USA

Two approaches to correlative species distribution models (MaxEnt and Multi-Model Framework) were used to predict global and local potential distribution of huanglongbing (HLB) caused by Candidatus Liberibacter asiaticus (CLas) and its vector the Asian citrus psyllid (ACP, Diaphorina citri Kuwayama). Long-term climate data were sourced from the Worldclim website. The global distribution of CLas and ACP was gathered from online databases, literature review and communication with specialists. Data on Clas and ACP distribution in the USA were not used in model calibration to allow model validation for independent locations. Both models successfully predicted Florida and coastal areas in the Gulf Coast states as highly suitable for Clas and ACP. The models also predicted that coastal areas in California were climatologically favorable for ACP and Clas, but less so than in Florida. When current USA presence data were included in the models, the suitable areas for ACP establishment expanded to the Central Valley, CA, while this area remained less conducive for CLas. Climate suitability was primarily related to rainfall and secondarily to temperature. Globally, both models predicted that climates in large areas of Africa, Latin America and North Australia were highly suitable for ACP and CLas, while the climate in the Mediterranean area was moderately suitable for ACP but less suitable for CLas, except for that in southern Portugal and Spain. Clas predictions from our models could be informative for countries like Australia, New Zealand, citrus-producing European countries and much of Africa, where CLas and D. citri have not been reported

Sporulation of Bremia lactucae affected by temperature, relative humidity, and wind in controlled conditions

The effects of temperature (5 to 25degreesC), relative humidity (81 to 100%), wind speed (0 to 1.0 in s(-1)), and their interactions on sporulation of Bremia lactucae on lettuce cotyledons were investigated in controlled conditions. Sporulation was affected significantly (P 0.5 in s(-1), regardless of RH. In still air, the number of sporangiophores produced per cotyledon increased linearly with RH from 81 to 100% (P = 0.0001, r = 0.98). Histological observations indicated that sporulation may be affected by stomatal aperture in response to RH, as more closed stomata and correspondingly fewer sporangiophores were present at lower RE. These results are important for understanding the mechanism of RE effects on sporulation and for predicting conditions conducive to downy mildew development

Projecting the suitability of global and local habitats for myrtle rust (Austropuccinia psidii) using model consensus

Myrtle rust (caused by Austropuccinia psidii) affects more than 500 known host species in the Myrtaceae family. Three different modelling approaches (CLIMEX, MaxEnt and Multi-Model Framework) were used to project the habitat suitability for myrtle rust at both global and local scales. Current data on the global occurrence of myrtle rust were collected from online literature and expert solicitation. Long-term averages of climate data (1960–1990) were sourced from WorldClim and CliMond websites. Recent reports of myrtle rust in New Zealand were used for validation of model outputs but not in model training and testing. The model outputs were combined into a consensus model to identify localities projected to be suitable for myrtle rust according to two or three models (hotspots). In addition to the locations where the pathogen is currently present, all models successfully projected independent occurrence data in New Zealand suitable for establishment of the pathogen. Climate suitability for the pathogen was primarily related to temperature followed by rainfall in MaxEnt and the CLIMEX model. The results confirmed the optimum temperature range of this pathogen in the literature (15–25 °C). Additional analysis of the precipitation variables indicated that excessive rain (more than 2000 mm in warmest quarter of the year) combined with high temperatures (>30 °C) constrain pathogen establishment. The results of the current study can be useful for countries such as New Zealand, China, South Africa and Singapore where the pathogen has not fully spread or established