Thermal Mediated Azoxystrobin Sensitivity Of Potato Late Blight Pathogen Phytophthora Infestans

Potato is a major food crop worldwide and plays vital role for effective food security towards alleviating hunger and poverty.However,diseases are one of the main limitations towards promoting of potato industries.Late blight,caused by Phytophthora infestans（Mont）de Bary,is regarded as the best notorious,greatly considered and yet the most damaging disease of potato.Management of late blight depends intensely on the application of chemical（synthetic）fungicides together with act of using of host resistance.Understanding how fungicide resistance arises in pathogen population is required for effective designing management strategies for preventing and minimizing plant diseases under the extreme environmental condition in the future.How fungicide resistance develops in pathogen populations are seriously influenced by biotic and abiotic factors like human activities and environmental temperature.This study was done to examine the relative influences of environmental temperature to the evolution of fungicide resistance,and infer the influence of ongoing global warming on fungicide effectiveness and plant diseases future management,and also aimed to examine the relative significance of genetic variations and phenotypic plasticity to fungicide resistance.We used azoxystrobin-P.infestans interaction in common garden study using statistical genetics approach and microsatellite molecular markers to evaluate evolutionary possibility of azoxystrobin sensitivity of180 isolates of P.infestans collected from nine geographical areas in China at five（5）experimental temperature schemes ranging from 13 to25℃.The results showed that local temperature contributed significantly to the differences in azoxystrobin tolerance among the P.infestans natural populations.Among-population and within-population variations of azoxystrobin resistance increased as experimental temperatures increased.The results further indicate that isolates with higher azoxystrobin tolerance adapt to a broader thermal niche,and temperature niche breadth(T_max-T_min)of azoxystrobin tolerance reduced with the increased of azoxystrobin concentration.Analysis for spatial distribution of quantitative genetic variation in fungicide tolerance with that of molecular variation obtained from SSR markers was conducted.The population genetic differentiation(Q_ST)in azoxystrobin tolerance was greater than the population genetic differentiation based on SSR marker loci(F_ST)indicated that the azoxystrobin tolerance of P.infestans to thermal adaptation has been affected by diversifying selection,and these different selection pressures forced the pathogens to select the specific genotype and phenotype in the local environment.The phenotypic plasticity from all the populations and on individual experimental temperatures is significantly higher than the heritability,which indicated that plasticity plays a better role in the environmental differences between the pathogens,and influence better adaptation of pathogens to evolution of fungicide resistance under the current diversifying selection.Diversifying selection on the azoxystrobin tolerance driven by local environmental temperature may additionally justify the non-correlation viewed（r=-0.057,P=0.741）between the Pairwise Q_ST and F_STin this study.In conclusion,as temperature in the experiment increased,spatial differentiation in azoxystrobin tolerance among P.infestans populations collected from various geographic regions also increased,this signifies that environmental temperature plays an essential role to the evolution of azoxystrobin resistance in P.infestans.Global warming is expected to escalate the evolutionary ability and spatial distribution of fungicide tolerance in pathogens and may enhance the threat of developing fungicide resistance,thereby increasing the difficulty for P.infestans management.Furthermore,controlling plant diseases in the future climatic conditions may experience severe challenges.