| Camellia oleifera anthracnose is one of the most diseases that could cause heavy leaves and fruit drop and lead to a significant reduction of seed production.Therefore,it causes huge economic losses to farmers.Traditionally,Colletotrichum gloeosporioides was recognized as the pathogen that causes Camellia oleifera anthracnose.In recent years,three new pathogens(C,fructicola、C.siamense and C.boninense)were found that may cause Camellia oleifera anthracnose.In this study,pathogens species constitution of Camellia oleifera and other host plants in oil-tea plantations were isolated and identified to confirm whether the anthracnose pathogens of other hosts could be a potential primary infection source of Camellia oleifera anthracnose.Finally,the genetic diversity of C.siamense from different hosts was analysed.The resules are as follows:(1)The isolation and identification of anthracnose pathogens in Hainan Province.A total of 34 strains were isolated from four oil-tea plantations in Hainan Province.Combining morphology,pathogenicity and multigene sequences indicated that the 34 strains were grouped into three species:C.fructicola(19 strains),C.siamense(14 strains)and C.camelliae(1 strain),and C.camelliae was the first report on Camellia oleifera.The biological characteristics of three pathogens were indicated that they adapt to the wide range of temperature and pH.The hyphae could grow in 10-35 ℃ and pH4.0-11.0 and growing fastest at 28 ℃.The most appropriate temperature and pH of the three pathogens are 25-30℃ and 6.0 respectively.Different light conditions are suitable for the growth of three pathogens.The light/dark treatment colony diameter is bigger than continuous illumination and continuous darkness’s.As a whole,C.siamense grows fastest,followed by C.fructicola,and C.camelliae grows the slowest.In addition,the conidium production of C.fructicola is maximum,followed by C.siamense,and C.camelliae is minimal.(2)The potential primary infection source of Camellia oleifera anthracnose in Hainan province.A total of 102 strains were isolated from different hosts of four oil-tea plantations in Hainan province.The 102 strains are grouped into four species,which are C.fructicola(66 strains),C.siamense(32 strains),C.gloeosporioides(3 strains)and C.cliviae(1 strain).Other hosts share the same pathogens(C.fructicola and C.siamense)with Camellia oleifera.The pathogenicity test indicated that those strains isolated from other hosts could infect Camellia oleifera.This showed that others hosts around oil-tea plantations were potential primary infection source of Camellia oleifera anthracnose.(3)The genetic diversity of C.siamense from different hosts.The analysis of genetic diversity of C.siamense from different hosts indicated that 68 strains sequence identified 14 haplotypes,and the major haplotype(H5)distribute in all of the host plants.It shows that C.siamense can asexual by diffusion between Camellia oleifera and other hosts in the same plantation or not in the same plantation.AMOVA analysis showed that the genetic variation mainly took place within the population,accounting for 81%of the total genetic differentiation.The analysis of genetic differentiation(Fst)indicated that there was a certain genetic differentiation between strains of different hosts of population.And mismatch distribution analysis suggested that C.siamense of Camellia oleifera and others hosts might experience large-scale population expansion.The phylogenetic analysis indicated that C.siamense from different hosts scattered distribution in the phylogenetic tree.Results of this study showed that the C.siamense natural population had rich genetic diversity and there was effective gene flow between the C.siamense natural population among different oil-tea plantations and different hosts.And it revealed that the pathogen could transfer between Camellia oleifera and other hosts. |
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