| Castor is one of the top ten oil crops in the world,which has high economic and medicinal value.In recent years,with the continuous development of castor industry,the castor planting area in the world is increasing year by year,and castor diseases and pests also occur one after another.It not only affects the normal growth of castor,but also seriously affects the sustainable development of castor industry.At present,there are few researches on castor fungal diseases in China.Therefore,it is of great significance to master the types of castor diseases for accurate diagnosis and scientific control of castor diseases in the future.In this paper,the castor diseases were investigated and studied in Zhanjiang City,Guangdong Province,and the samples from Shandong and Inner Mongolia were identified.The main findings are as follows:1.Disease investigation.From 2018 to 2020,a five-point sampling method was used to investigate the disease in the seedling greenhouse of Guangdong Ocean University,the west campus of the campus,and the castor planting base in Huguang Town,Zhanjiang City,Guangdong Province.According to the investigation,9 kinds of diseases with different symptoms were found,including 1 disease at seed bud stage,1 disease at seedling stage,1 disease at root stage,2 diseases at stem stage and 4diseases at leaf stage.2.Identification of pathogen species.The isolate was obtained by conventional tissue separation method,and the pathogenicity was determined according to Koch’s method.At the same time,combined with morphological characteristics and ITS,TEF-1α,TUB,ACT,TUB,RPB2,GAPDH and other gene sequences for analysis.Neighbor-joining method in Mega 7.0 was used to construct phylogenetic tree for pathogen classification and identification.The results showed that the pathogen causing castor seed bud rot,castor seedling damping-off and castor root rot were all Fusarium solani;the pathogen causing castor branch blight was Lasiodiplodia theobromae;the pathogen causing castor stem blight was Diaporthe ueckeri;the pathogen causing castor Cladosporium leaf spot was Cladosporium tenuissimum;the pathogen causing castor anthracnose leaf spot was Colletotrichum siamense;the pathogen causing castor Corynespora leaf vein spot was Corynespora cassiicola;the pathogen causing castor Phyllosticta leaf spot was Phyllosticta capitalensis.At the same time,the pathogen causing castor Fusarium wilt in Shandong was identified as F.oxysporum;the pathogen causing castor stem rot in Inner Mongolia was Alternaria alternata and Trichothecium roseum.3.Hazard degree.Among the 9 fungal diseases,seedling damping-off,anthracnose leaf spot,seed bud rot,root rot and branch blight are the most common and severely harmful diseases,with incidence rates of 40.5%,38.0%,28.1%,26.0%and 24.0%,respectively,which are the main diseases on castor.The other Corynespora leaf vein spot,Phyllosticta leaf spot,Cladosporium leaf spot and stem blight are less harmful,with incidence rates of 21.6%,18.3%,18.0% and 14.0%,respectively,which are the secondary diseases on castor.Cladosporium leaf spot,anthracnose leaf spot and Corynespora leaf vein spot were reported for the first time in China,while the other six diseases were new diseases on castor,which were reported for the first time in the world.4.Laboratory control experiment of diseases caused by F.solani.In this study,the chemical control experiment of F.solani was carried out.The castor seeds were soaked or not soaked with 11% spermatophore pyrimidine fungicide produced by Baolu company,and the pot experiment was carried out with or without irrigation after the disease at seedling stage.The results showed that the incidence rate of seed buds and castor seedlings treated with 11% spermatophore pyrimidine fungicide was lower than that treated with no pesticides,which could reduce the occurrence of disease and prevent the castor seed bud rot and castor seedling damping off caused by F.solani. |
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