| The aim of the present study was to to understand the impact of climate change on the distribution of diseases and insect pests and their hosts,and analyze their response to climate change,so as to provide scientific support for inspection and quarantine,prediction and effective prevention and control of important diseases and insect pests.In this study,Pseudomonas syringae pv.Actinidiae(Psa)and Candidatus Liberibacter asiaticus(Clas)were selected as the research objects,and the feasibility of using species distribution model to simulate the distribution and change of two plant pathogens in large scale under the background of climate change was discussed.MaxEnt was used to simulate the geographic distribution of target species in China under current climate condition and three future climate scenarios.The distribution data were obtained by searching the species distribution database,digital specimen platform,and consulting publicly published journal papers,dissertations and literature.Modeling variables were selected according to the biological characteristics of the species,the initial contribution rate and the Pearson’s correlation coefficient.Theoretical evaluation,field investigation and independent samples were selected to verify the accuracy of the model.From the perspectives of pathogens-host plants and pathogens-vector insects,the consistency and difference of the geographical distribution of the two were analyzed.Jackknife test was used to screen the dominant variables,analyze their impact on species distribution.The distribution range and spatial pattern of the target species under three climate scenarios in the future were compared and analyzed.The main conclusions are as follows.1)The AUC(Area under curve)values of all models constructed in this research were higher than 0.9,TSS(True skill statistics)values were higher than 0.8,and Kappa statistics were higher than 0.6.Three theoretical evaluation indicators indicated that the model performs well.Field investigation showed that the accuracy of MaxEnt model of Psa was 89.57 %.The evaluation of independent samples of Actinidia chinensis,Actinidia deliciosa and Actinidia arguta showed that the accuracy of simulation was higher than 80 %.The above results indicated that MaxEnt performs well and can be used in this study..2)Jackknife test showed that the min temperature of coldest month was the most critical climatic variable that affects the geographic distribution of Psa.The highly suitable areas of Psa were mainly located in Hubei,Guizhou,Sichuan,Chongqing,Hunan,Anhui,Zhejiang and Jiangsu under current climatic condition,covering the main producing areas of kiwifruit in China.and there would be great pressure on prevention and control in the future.There were significant differences in the area and proportion of overlapping area between Psa and three kinds of kiwifruit.Among them,A.arguta was the most widely distributed,and there were large separate distribution areas in Sichuan,Shanxi,Liaoning,Jilin and Heilongjiang,so its planting scale can be expanded according to actual conditions.3)Under climate change scenarios,the areas of highly and total suitable areas of Psa would increase significantly,and the centroids of moderately highly and total suitable areas would move to the north,indicating that climate warming in the future would expand the suitable range of Psa.Compared with the current situation,the climate risk index of Psa in the main kiwifruit planting provinces in China would be on the rise,indicating that climate change would promote the occurrence and prevalence of the disease in some regions.Under the climate change scenario,the responses of A.chinensis,A.deliciosa and A.arguta to climate change were significantly different.In the next three scenarios,the area of highly suitable areas of A.chinensis would decrease,while that of A.deliciosa and A.arguta would increase.In the future,the centroids of the three species of kiwifruit would move to high latitude,but the moving distance and angle were quite different.It reminds us that the impact of climate change should be fully considered in the adjustment of agricultural planning.For the climate sensitive areas,the relevant departments should issue corresponding guidance programs to cope with climate change by adjusting the planting varieties and scale.4)According to the selected dominant climatic variables and their response curves,the distribution of Clas was not only most related to precipitation variables,but also affected by extreme temperature variables,which jointly determined the geographical distribution of Clas.The response curves of the dominant climatic variables affecting the distribution of Diaphorina citri showed that low temperature in winter and high temperature in summer were the key variables limiting its distribution.The suitable areas of Clas were more widely distributed and had higher latitude than those of D.citri.The investigation of Clas and the control of D.citri should be strengthened in the overlapping areas.For the separate distribution areas of Clas,especially in Sichuan,Chongqing and Hubei,the long-distance access of infected seedlings should be strictly prevented.5)Under climate change scenarios,the suitable areas of Clas were more stable than current situation.Most of the main citrus production areas in China were located in the suitable areas of Clas,and the climate risk level would be maintained at a very high level.The suitable areas of D.citri would increase in the future,and the centroid would move to the north.This indicated that the increase of temperature in winter would expand the geographical distribution of D.citri,which would accelerate the spread of Clas and expand its distribution range. |
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