Identification Of Colletotrichum Population Associated With Maize In Sichuan Province

Maize anthracnose is mainly caused by the Colletotrichum species;however,the field symptoms produced by this disease are similar to Curvularia leaf spot and Bipolaris corn leaf spot.In 2015,we collected large number of samples showing typical above ground leaf spot disease symptoms and found that the isolates number of Colletotrichum were relatively higher,which attracted us to think about whether the Colletotrichum was the main pathogen of maize or the maize anthracnose is mixed with leaf spot disease complex.In current study,samples were collected from 20 counties of 12 cities in the main maize producing areas of Sichuan Province,from 2015 to 2017,in order to identify the population structure of Colletotrichum species associated with maize in Sichuan Province,and to provide a scientific foundation for the diagnosis and control of leaf spot of maize.A total of 99 isolates were obtained after tissue separation and single-spore isolation techniques.Morphological identification and multi-locus phylogenetic analyses were used for all isolates,including the nuclear ribosomal internal transcribed spacer(ITS)region,β-tubulin(TUB2),actin(ACT),glyceraldehyde-3-phosphate dehydrogenase(GAPDH)and calmodulin(CAL).Then total of 99 isolates were identified as 10 species: C.cliviae(24strains,24.2%),C.fructicola(18 strains,18.2%),C.karstii(16 strains,16.1%),C.siamense(13 strains,13.1%),C.boninense(7 strains,7.1%),C.kahawae(7 strains,7.1%),C.brevisporum(6 strains,6.1%),C.truncatum(5 strains,5.1%),C.gigasporum(2 strains,2.0%)and C.gloeosporioides(1 strain,1.0%).Among 10 species,C.cliviae was the predominant species.As a result of pathogenicity test,only C.siamense and C.truncatum could cause leaf spot on maize,so they were considered the pathogen of maize anthracnose.In addition,to the best of our knowledge,C.simense and C.truncatum were recorded for the first time as the cause of anthracnose on maize in China.The other 9 species could infect Pyrus pyrifolia and 6 of 9 species could infect Malus domestica Mill except C.boninense,and these results indicated that the other 9 species except C.boninense were non-host-specific.Among the other 8 species that could not infected maize were C.cliviae,C.fructicola,C.karstii and C.boninense and were isolated from healthy maize leaves,so we identified them as endophyte.