Molecular Identification And Chemical Control Of Pepper Mosaic Disease In Hainan

Black pepper(Piper nigrum L.),known as "King of Spices",is an important commercial spice crop with its economic life for 20 to 30 years.At present,the harvest area and output of black pepper in China have ranked at sixth and fifth in the world,respectively.The area of Hainan pepper production accounts for more than 90%of the whole country.Pepper mosaic disease,caused by ccumber mosaic virus(CMV)is one of the important diseases on the production of pepper and the occurrence of the disease tends to be serious in Hainan.System researches about the distribution,variation and chemical control of the disease are still lack.The status of the pepper mosaic disease in Hainan was surveyed.The full-length cDNA sequences of genomic RNAs of 4 pepper mosaic disease isolates were determined by RT-PCR and sequence analysis.Virus artificial inoculation and chemical control were also studied.The main results are as follows:(1)A survey on the status of the pepper mosaic disease was carried out during 2014?2015 in Hainan Province.The results showed that the pepper mosaic disease had occurred in the above cities and the main symptoms were mosaic,yellowing,mottle,blade decrescent,narrow,winding shrivel,shorter internode,slow growth,etc..The incidence of the disease in most pepper plantations was about 10%?20%while it reached 87.5%in the serious pepper garden.The highest incidence was up to 36%in Qionghai and the lightest was 7.5%in Wanning.The incidence of the whole hainan area is 14.4%.The survey also found that the incidence of the pepper garden interplanted such as arecanut,litchi and lemon was 9.9%,and the incidence of the single mode of pepper garden was 16.8%.(2)The full-length cDNA sequences of genomic RNAs of CMV-WN,DA,FT and DS isolates were determined by RT-PCR and sequence analysis.The RNA1 of CMV-WN,DA,FT and DS RNA1 consisted of 3359?3361 nucleotides(nt),and encoded protein 1a.RNA2 consisted of 3042?3048 nt,and encoded protein 2a and 2b.RNA3 contained 2216?2224 nt,and encoded protein 3a and CP.The RNA sequence similarity of CMV-WN,DA,FT and DS isolates was highest with the corresponding RNAs from CMV-SD strain.The phylogenetic tree analyses of the RNA1,RNA2 and RNA3 showed the evolutionary relationship of the Hainan isolate and CMV IB was nearest,while the phylogenetic tree analyses of the RNA1 and RNA2 showed that CMV-WN,FT,DS and CMV-DA were in a different branch.Based on the 5'NTR structure of RNA3,the phylogenetic tree analyses of 5'NTR nucleotide sequences of RNA3 and CP amino acid sequences,CMV-WN,DA,FT and DS isolates were classified into CMV IB subgroup.The phylogenetic tree analyses of CP amino acid sequences also showed CMV-WN,FT,DS and the Yunnan isolate of pepper CMV-YNP gathered into the same cluster while CMV-DA and the Hainan isolate of pepper CMV-HNP were in a separate branch.(3)The healthy pepper seedlings were inoculated artificially by CMV.The results showed that all the processing had not appeared the disease symptom,and the ELISA results were negative.(4)The chemical experiments against CMV showed that the effectiveness of the four chemicals including 20%hydrochloric acid copper Moroxydine,8%Ningnanmeishu(mixed VitaCat,Anngro,Zn),Dufulin,Atailing was 47.0%,44.6%,48.1%,51.6%,respectively,and there was no significant difference among the four pesticides by Duncan's Multiple-Range test of SAS 9.2.