| Tea-oil tree(Camellia oleifera Abel)is a unique edible oil woody plant in China and one of the four largest edible oil woody crops in the world.It has the reputation of "Oriental olive oil" and is widely distributed in the south of the Qinling and Huaihe Mountains in China,with high economic value,medicinal value,and irreplaceable ecological value.Anthracnose is one of the main threatening diseases of tea-oil tree in various regions of China,which seriously restricts the sustainable development of the Ca.oleifera industry.Currently,there are 11 species of pathogenic fungi of Ca.oleifera anthracnose have been reported,and there are significant differences in the species of pathogenic fungi of Ca.oleifera anthracnose in different regions.In order to clarify the species composition,distribution,and genetic structure of dominant populations of anthracnose in the main Ca.oleifera producing areas of Jiangxi Province,this article collected and isolated anthracnose from 11 main Ca.oleifera cultivation areas in Jiangxi Province,identified the pathogenic fungi through a combination of morphology and polygenic systematics,and analyzed the genetic structure of dominant populations,with a view to clarifying the species composition and distribution of anthracnose in Jiangxi Province,to elucidate the population genetic differentiation rules of dominant species of Ca.oleifera anthracnose,and provide theoretical basis for the rational prevention and control of Ca.oleifera anthracnose in Jiangxi Province.The main results of the study are as follows:(1)Identification of the pathogenic species of Ca.oleifera anthracnose in Jiangxi Province.A total of 271 strains of Colletotrichum fungi were isolated from 11 counties and cities in Jiangxi Province.The method of combining morphology with multiple gene sequences(ITS,GAPDH,TUB2,CAL,ACT,CHS-1)was used to identify Colletotrichum fungi.The results showed that the Colletotrichum causing Ca.oleifera in Jiangxi Province belonged to three types of complex species,of which 97.42% were C.gloeosporioides species complex,(Cgc),and 1.85% were identified as C.boninense species complex,(Cbc),0.74% of the isolates were C.orchidearum species complex(Coco).It was divided into 9species,among them,it belongs to C.fructicola(71.97%),C.siamense(18.18%),Ca.camelliae(6.44%),C.aenigma(0.76%),C.wuxiense(0.76%),C.horri(0.76%),and C.alienum(1.14%).In Cbc,it belongs to C.karstii(100%),Cox.C is C.plurivorum(100%),Among them,C.fructicola had the widest distribution and the highest isolation rate(70.11%),which belonged to the dominant species of Ca.oleifera anthracnose in Jiangxi Province.C.wuxiense,C.alienum and C.plurivorum were three new host species.Nine representative isolates of Colletotrichum were randomly selected to conduct pathogenicity experiments with isolated leaves and potted Ca.oleifera seedlings as inoculation materials.The results showed that all the nine representative isolates of Colletotrichum could cause disease on injured leaves,and the leaves of Ca.oleifera without injury were not diseased or the incidence was low,indicating those Ca.oleifera anthracnose were mostly weakly parasitic.(2)Analysis of genetic structure of C.fructicola population,which is widely distributed in Jiangxi Province.A total of 186 strains of C.fructicola isolated from samples of Ca.oleifera in Jiangxi Province were isolated based on three genes(internal transcribed spaces,ITS;465 bp),glyceraldehyde-3-phosphate dehydrogenase(GAPDH;216 bp),β-Tubulin(TUB2;427 bp)and a total of 1176-bp fragments were analyzed.The results showed that the sequence included 1069 conserved sites,44 polymorphic sites,3 parsimonious information sites,and 41 singleton sites,a total of 11 haplotypes were defined,haplotypes Hap1 and Hap2 are distributed in a star-shaped distribution.,and a haplotype diversity(Hd)is 0.45237.Nucleotide diversity(Pi)is relatively low,with a value of 0.00082.Analysis of molecular variance showed that 94.43 % of the variation was caused by within population differences.The test results of Fu and Li ’s D(-8.10550,P < 0.05)and Tajima ’s D(-2.617,P < 0.001)followed the neutral evolution model,and the population of C.fructicola conformed to the population expansion model.The genetic differentiation coefficient FST between populations was 0.0557,and the gene flow Nm was 4.24,indicating that there was moderate genetic differentiation between populations and frequent gene exchange.The results of correlation analysis between geographical distance and genetic distance showed that there was no significant correlation between the genetic diversity of C.fructicola strains and their geographical origin.In this study,the methods of morphology and multi-gene phylogenetic analysis were used to systematically identify the species of anthracnose infecting Ca.oleifera in Jiangxi Province,and three species were found to be new records of Ca.oleifera anthracnose.The results enriched and deepened the understanding of Ca.oleifera anthracnose in Jiangxi Province,and provided a theoretical basis for guiding the prevention and control of Ca.oleifera anthracnose and the development and utilization of resistant varieties of Ca.oleifera in the future. |
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