The Adaptation Of Phytophthora Infestans To Analysis Of Ultraviolet Irradiation

Potato(Solanum tuberosum L.)is the third-ranked food crop globally.Late blight caused by Phytophthora infestans(Mont.)de Bary is the most destructive disease of potato worldwide.The amount and distribution of genetic variation in P.infestans populations is one of the key factors influencing the occurrence and epidemic of potato late blight.Due to ozone layer deletion,ultraviolet(UV)irradiation has been increased in recent years.To infer the impact of UV irradiations on the disease epidemic of late blight under changing environment and provide evolutionary guidance for sustainable potato late blight management.We analyzed 20 each clonal lineages in the seven Phytophthora infestans populations sampled from Fuzhou Fujian,Ningde Fujian,Anshun Guizhou,Nanning Guangxi,Guyuan Ningxia,Dingxi Gansu and Qujing Yunnan to determine the amount and distribution of genetic diversity in UV adaptation in the pathogen.In addition,a new approach(MatArea)was developed to quantify the colony size of Phytophthora infestans using the image processing function embedded Matlab.Image results estimated from the new approach were compared to those from Assess software recommended by American Phytopathological Society and cross-intersection.The main results are as follows:1.Analysis of UV adaptation indicates the growth rate of isolates collected from Guyuan Ningxia,Nanning Guangxi and Fuzhou Fujian was enhanced under 30s UV treatments.The growth rate of the isolates from Qujing Yunnan was not significantly affected under seven UV treatments shemes.Population differentiation for UV adaptation(QST)was 0.94,which was significantly higher than the population diffeerentiation for neutral SSR markers(FST)was 0.12,illustrating adaptation to UV irradiation in Phytophthora infestans was under diversifying selection according to local environments and natural selction favoring for specific genotype and phenotype best adapted to local UV irradiation can lead to local adaptation.2.The aggressiveness of P.infestans was significantly reduced under 180 seconds UV treatment in all but isolates collected from Qujing Yunnan,illustrating UV irradiation in Phytophthora infestans s can prolong the incubation period.4.The mean coefficient of variance for colony size estimated from Assess calibrated from one photos,Assess calibrated by photos,cross-intersection and MatArea were 7.67%,4.42%,3.58%and 0%,respectively,suggesting that MatArea can provide a quick estimation of colony size with higher accuracy and reproducibility.The MatArea estimation was also less affected by the inoculation method,colony morphology and size than Assess estimation.These results suggest that MatArea is an effective way to measure large amounts of digital data such as required by the statistical genetic study of plant pathogens.