Studies On Population Diversity Of Colletotrichum Species On Chili Pepper And Botrytis Cinerea From Three Hosts In China

Anthracnose caused by Colletotrichum species is a serious disease of many plants.Several Colletotrichum species have been reported to infect chili pepper in different countries.Although China is the largest chili pepper producing country,little is known about Colletotrichum species infecting chill pepper across the country.Grey mold is also an important disease on many host plants.In this study,we investigate the population structure of Colletotrichum species on chili pepper in China,fungicides sensitivity,and population genetic diversity of C.truncatum and Botrytis cinerea.We collected samples of diseased chili pepper tissue from 29 provinces in mainland China and obtained 1285 isolates.The morphology of all isolates was investigated,and multi-locus phylogenetic analysis(ITS,ACT,CAL,CHS-1,GAPDH,TUB2,HIS3)was performed on representative strains.At least 15 species were identified;the most prevalent species were C.truncatum,C.fructicola,C.gloeosporioides,C.scovillei and C.fioriniae.Three new species,C.conoides,C.grossum,and C.liaoningense,were discovered and described.C.incanum,C.aenigma,C.karstii,C.hymenocallidis,C.endophytica,C.viniferum and C.cliviae were reported for the first time on chili pepper.C.fructicola,C.scovillei and C.fioriniae were reported for the first time on chili pepper in China.All tested isolates were pathogenic on detached,inoculated chili fruits,except C.endophytica,which was originally reported as an endophytic fungus.266 C.truncatum isolates from 13 regions representing the main pepper-growing areas throughout China were obtained and analyzed.The analysis based on nine microsatellite markers identified high intra population genetic diversity,evidence of sexual recombination,and geographic differentiation.The genetic differentiation was positively correlated with geographic distance,with the southern and northern China populations grouped intwo distinct clusters.Populations from Southern China were less sensitive to the fungicide prochloraz than those in the North,However,sensitivity to prochloraz was positively correlated with mycelial growth rate in the absence of the fungicide.Interestingly,isolates collected from the pepper-breeding center harbored more private alleles than other isolates.The sensitivities were determined for the 15 Colletotrichum species isolated in this study to eight fungicides.Among the 15 species,C.truncatum was the least sensitive to fungicides and was especially insensitive to tebuconazole and myclobutanil.The other 14 species were sensitive to most of the fungicides.Among the eight fungicides,prochloraz was most effective for inhibition of Colletotrichum species.The frequency distributions of five dominant species of Colletotrichum sensitivity to five DMIs(as indicated by EC50 values)were all unimodal curves and indicated that there was no reduced sensitivity subgroup in the field.Amplification and comparison of the cyp51 gene from C.truncatum with C.gloeosporioides and C.scovillei,showed that 14 different amino acids were found.It can be inferred that the differences might contribute to the low sensitivity of C.truncatum to tebuconazole and myclobutanil.393 B.cinerea isolates of 28 populations throughout China from tomato,cherry and nectarine were obtained and analyzed.The analysis based on 14 microsatellite markers identified high intra population genetic diversity,clonal spread,no evidence of sexual recombination and genetic differentiation,but population differentiation according to host of origin was present.No correlation was found between population genetic distance and geographic distance.Closely phylogenetic relationship was found between 2011 and 2012 populations of Liaoning province,which indicated that population of B.cinerea had a slowly variant rate in this region.However,it was contrary for Fujian and Shanghai populations,which showed fast variant rate.