Population Structure Of Phytophthora Infestans In Sichuan,china And Sensitivity Of Selective Strains Under Fungicide Stress

Late blight disease caused by Phytophthora infestans continues to pose a great challenge for potato and tomato growers around the world.Despite the numerous efforts conducted to alleviate the losses caused by this disease,the pathogen's diversity has been a key factor in disease control failures.Continuous monitoring of pathogen traits such as fungicide sensitivity and host preference are essential for selecting the best disease management methods.The overall objective of this study was to understand the P.infestans population in Sichuan,being one of the important potato producing province in western China.Information on pathogen genetic diversity and population structure are important to understand the possible potential of pathogen populations to extend and alter host resistance.High biodiversity may give grounds for emergence of new genotypes with unique biological characteristics,with changes in pathogen fitness or resistance to certain fungicides.Keeping in view the importance of Sichuan province for potato production and pace of late blight disease,the following study was aimed:(1)To investigate the changes in population structure of P.infestans in Sichuan with 12 SSR markers;(2)To reveal the genetic diversity among P.infestans isolates;(3)To investigate the proportion of A1 and A2 mating types with the self-fertile isolates;(4)the existence of sexual reproduction in recent years.Moreover,knowledge of the sensitivity,evolution and resistance of fungicide is important in securing sustainable disease management in agricultural systems.So,in this study,we also analyzed a few known strains,in vitro,of P.infestans obtained from previous studies.The strains belong to Netherlands and China,selected on the basis of their phenotypic and genotypic characters to study their sensitivity against the fungicides that are used most frequently by farmers in the potato fields of China.The objectives of this experiment were aimed to determine the(1)role of genetic heritability and plasticity of the P.infestans strains in response to the fungicides;(2)the effect on the mycelial growth rate over 20 week time under fungicide stress conditions;(3)SSR analysis on fungicide treated and untreated strains of P.infetsnas.The overall results of the study shows that the Sichuan population of Phytophthora infestans is dominated by highly virulent and resistant clonal lineage Blue-13(13-A2)and self-fertile isolates and the selected strains were found sensitive but reduced SSR allelic change suggesting low evolution.