The Identification Of Alternaria On Vegetable And The Research Of New Diseases In China

Alternaria species are major pathogens causing vegetable diseases worldwide,especially the large-spored species,which can cause severe vegetable black spot diseases and lead to huge economic losses.At present,the identification of Alternaria species is still incomplete.The occurrence of diseases caused by Alternaria species in China was investigated,and the pathogens were identified through sporulation patterns and molecular biological assays.Simultaneously,the methods of identifying Alternaria species was improved so as to lay a foundation for the future classification and identification of Alternaria species.The main results were as follow:1.The pathogens of Alternaria species sampled from some provinces in China were clarified.From 2015 to 2017,more than 700 diseased samples of different vegetables caused by Alternaria species were collected from 15 regions of eight provinces including Tianjin,Shandong,Inner Mongolia,Beijing,Hebei,Gansu,Xinjiang and Henan.219 strains were isolated,of which 78 were small-spored species and other 141 were large-spored species.Seven different species of Alternaria were identified,namely A.brassicicola,A.brassicae,A.tenuissima,A.alternata,A.solani,A.tagetica and A.dauci.The field symptoms and pathogens of severe damaging diseases were described in detail.2.Six genes were revealed to be suitable for molecular identification of vegetable diseases caused by Alternaria species and the traditional morphology method of identifying the sporulation patterns of the Alternaria species was optimized,The sporulation patterns was observed following the optimized procedure below:when the colony covers 3/4 of the PCA culture dish,the surface mycelium was scraped off to stimulate spores.Then,the sporulated culture was smeared around a central hole of a filter paper to obtain the sporulation patterns.In this study,12 genes utilized in the taxonomic study of Alternaria including ITS,GAPDH,RPB2,endoPG,Alt α 1,TEF1,TEF2,OPA2-1,OPA10-2,OPA1-3,ATPase,and CAL were tested in the taxonomic study of Alternaria.Six genes of ITS,GAPDH,RPB2,TEF1,endoPG,and Alt α 1 were evaluated to be suitable for the identification of the pathogens of related diseases.3.The three new records of vegetable diseases and the causing pathogens were identified.Three new diseases include lettuce leaf spot disease caused by A.solani and A.brassicae,lettuce root rot caused by A.tagetica and A.brassicae,and okra leaf spot caused by A.alternata.Therefore,clarification of specific pathogenic species of vegetable diseases will serve an important role in the combat of vegetable diseases.