Over-Summering Regionalization And Population Genetic Structure Of Puccinia Triticina In China

Wheat leaf rust is a fungal disease caused by Puccinia triticina（Pt）,which is spread by air.In recent years,with the change of climate and farming system,the damage of wheat leaf rust is becoming more and more severe.It is of great significance for the prediction and integrated management of wheat leaf rust to carry out the analysis on key meteorological factors determining over-summering of Pt,on the temperature sensitivity of Pt populations,on the over-summering region classification of Pt and on the genetic structure of Pt populations.In this study,the average day-temperature and the average maximum day-temperature of the hottest ten-days from July to August of 698 meteorological stations were used in linear regression analysis,and the mean values of wind speed,precipitation,sunshine time and relative humidity from July to August on spatial interpolation were carried out.The meteorological data of 93 investigation sites of wheat leaf rust were obtained afterwards.Then the correlation analysis was carried out between over-summering and meteorological factors.The results showed that over-summering had a significant correlation with the average day-temperature and average maximum day-temperature of the hottest ten-days from July to August（P<0.01）,but had no significant correlation with other meteorological factors（P>0.05）.The results provided the theoretical basis for the temperature-based evaluation of over-summering region classification of Pt.Wheat leaf rust strains from 12 provinces（municipalities,autonomous regions）were isolated and purified and sprayed on wheat seedlings.After 10 days of cultivation at different temperatures,the disease severity of leaves was investigated,the disease inhibition rate was calculated,and the linear regression analysis between disease inhibition rate and temperature was carried out.According to the regression equation,ET₅₀ and ET₁₀₀ were calculated.The results showed that the average ET₅₀ and ET₁₀₀ were 23.83℃and 27.34℃respectively,and the tested temperature didn’t exert selection pressure on Pt populations.The results provided basic data for the over-summering region classification of Pt in China.Based on the threshold of disease termination temperature at 27.34℃,the over-summering regions of Pt were analyzed by Arc GIS.The results showed that the over-summering area of Pt extended from southwest to northeast,forming a long and narrow main over-summering belt,including the whole territory of Yunnan,western Guizhou,central Sichuan,southeast Gansu,central and northern Shaanxi,southern Ningxia,most of Shanxi,central Inner Mongolia,western and northern Hebei,etc.In addition,the genetic structure of 168 Pt isolates collected from Henan,Inner Mongolia,Jiangsu,Anhui,Hubei,Yunnan and Guizhou provinces（municipalities,autonomous regions）in 2019 was analyzed by using 13 SSR molecular markers.The results showed that Pt populations indicated high genotype diversity and evenness,and the main source of variations were from variations within the populations.The reproductive mode of the population in each wheat area was asexual reproduction.The genetic distance of the Pt populations in northern spring wheat area,Huanghuai winter wheat area and winter wheat area of the middle and lower reaches of the Yangtze River was closer,and the gene exchange was more frequent.With Pt populations in winter wheat area of the middle and lower reaches of the Yangtze River as a bridge,Pt populations in southwest winter wheat area communicated with that in northern spring wheat area and Huanghuai winter wheat area.