The Studies Of Tomato Disease Caused By Virus And Phytoplasma In Xinjiang

The study on tomato disease caused by virus and phytoplawmas had been done:Three types of viral symptoms showing mosaic, fern leaf and necrotic streak were found on processingtomato in Xingjiang through field investigation. Tomato necrotic streak disease causes the most seriousdamage although it occurs at the latest. Effect of sowing date on tomato virus disease was investigated inShihezi in2007-2009. The results showed that there are significant differences among three sowing dates.The incidence rate(67.94%) and disease index(43.47) of processing tomato sowing on May20th(latesowing period)are higher than those of processing tomato sowing on April5th (early sowing period) or onApril25th (proper sowing period).15processing tomato cultivars resistance to virus diseases wereinvestigated. The result showed there existed definite differences in resistance among cultivars, althoughall tested cultivars had no obvious resistance to virus diseases. Four cultivars of ‘Lige-87-5’,‘Shifan15’,‘Tunhe4’ and ‘Shifan18’ showed relatively high disease index (64.03～65.77) in the field while the fourcultivars of ‘Xinfan9’,‘Xinfan4’,‘Q027’ and ‘Shifan3’ showed relatively low disease index (44.02～45.47) in the field.Detection method for Tobacco mosaic virus (TMV), Tomato mosaic virus (ToMV), Cucumber mosaicvirus (CMV), Potato virus Y (PVY) and Broad bean wilt virus (BBWV) was established, respectively.Seeds of15processing tomato cultivares were used to detect for the five viruses. The results showed thatonly ToMV can be detected from11cultivares seeds. It concluded that seed-borne ToMV is one of theprimary infection sources. More than400infected plants collected from fields were detected for species ofvirus during2009-2012. It showed that plants infected by ToMV (88.75%) were more than that infected byTMV (2.50%) and processing tomato virus diseases mainly resulted from the mixed infection of ToMVand other two viruses (CMV+PVY、CMV+BBWV、PVY+BBWV).Isolate XJT-1of ToMV、isolate XJ14-3of BBWV2and isolate SFQT1-2of CMV were obtained bybiological method from processing tomato plant showing necrosis streak symptoms. Genome sequences ofthe three isolates were cloned and sequenced. Genomic complete sequences of isolate XJT-1wascomprised of6383nucleotides (FN915865)and had the highest nucleotide sequence identities(98.7%-99.3%) with sequence of ToMV from Genebank. Genomic RNA1and RNA2of isolate XJ14-3were determined. RNA1consisted of5955nucleotides (FN985164) encoding a polyprotein with1870amino acids residues and shared78.6%-92.4%nucleotide sequence identities with RNA1of other BBWV2.RNA2consisted of3635nucleotides (HQ283389) encoding a polyprotein of1064amino acids residues andshared79.9%～97.4%nucleotide sequence identities with RNA2of other BBWV2. The genome of CMVisolate SFQT1-2contained three positive single stranded RNA. RNA1consisted of3356nucleotides(HQ283392) encoding1a protein and had the highest sequence identities with typical strain which belongsto CMV subgroup Ⅰ A. RNA2consisted of3042nucleotides (HQ283391) encoding2a protein and2bprotein. RNA3contained of2219nucleotides (HQ283393) encoding movement protein (MP) and coat protein (CP). RNA2and RNA3of isolate SFQT1-2shared high sequence identities with typical strainwhich belongs to CMV subgroup Ⅰ B.Phylogenetic analysis of CP revealed that SFQT1-2belongs to CMVsubgroup IB．Tomato plants with yellow leaf curl symptom collected from greenhouses in Kaishi were detected byPCR using universal primers of geminivirus to determine virus species. Amplified products about500bpwere amplified from8tomato samples, and KS2-5was chosen to clone and sequence. The sequencesconsisted of543nucleotides. It shared99.5%nucleotide sequence identities with DNA-A of Tomatoyellow leaf curl virus (TYLCV). Isolate KS2-5was chosen to determine complete sequence of DNA-A, itcomprised2781nucleotides (JQ807735)and had typical genomic organization of begomoviruses.Sequence comparison showed that DNA-A of KS2-5had98.6%-99.5%sequence identities with those ofTYLCV isolates, while less than75.4%identities with other begomoviruses. It was concluded that tomatoyellow leaf curl disease was caused by TYLCV in Xinjiang Kashi.Two tomato plants (SYC-1，ZYT-3) showing arbuscular, little leaf and floral organ deformity weredetedcted for phytoplasmal16S rRNA genes using PCR with universal primers R16mF2/R16mR1. DNAfragments of about1400bp were amplified from the two pants and sequenced. The results showed theyshared99.8%nucleotide sequence identities each other and had the highest nucleotide sequence identities(98.4%) with Clover proliferation group (16SⅥ). The16S rRNA gene of tomato phytoplsama had identicalpatterns with typical strain (AY39021) of subgroup16SⅥ-A with online analysis of iPhyClassifier forgenomic of16S rRNA. Phylogenetic analysis with genomic of16S rRNA gene showed they were locatedthe same branch with subgroup16SⅥ-A. All these results indicated that the phytoplsama associated withtomato belongs to the subgroup A of ‘Clover proliferation group’(16SⅥ).