3252

3161

كارشناسي ارشد

﴿ بيماري شناسي گياهي ﴾

اصفهان: دانشگاه صنعتي اصفهان، دانشكده ي كشاورزي

1384

سيزده، 84، [II]ص.: مصور، جدول

ص. ع. به فارسي و انگليسي

علي آهون منش ، هاله هاشمي سهي

حشمت اله رحيميان

امير مساح، رضا زارعي

1395/08/25

كتابنامه

كشاورزي

مهندسي كشاورزي

ID3161

به فارسي و انگليسي : قابل رويت در نسخه ديجيتالي

Abstract Exocortis is one of the most important citrus diseases which has spread to severalcitrus growing areas of the world Typical symptoms of the disease are bark scaling anddwarfing of citrus trees budded on trifoliate orange rootstock and stunting of the entirecitrus trees Exocortis like symptoms have been observed in several citrus orchards inMazandaran province The possible viroid etiology of the disease has beendemonstrated through graft and mechanical transmission of the agent into Etrog citron Lycopersicon esculentum cv Rutgers and Gynura sarmentosa as well as observedviroid like RNA bands following gel electrophoresis However the identity of theviroids occurring in citrus trees in Iran has remained undetermined Therefore molecular characterization and identification of exocortis disease agents in the north ofIran would help in better understanding the disease In response to presence of Citrustristeza virus CTV in Mazandaran there is an ongoing trend toward the use ofPoncirus trifoliata and its hybrids as rootstock in the north of Iran On the other hand these rootstocks are sensitive to exocortis disease Thus development of rapid andsensitive methods for detecting the exocortis and similar viroid in citrus trees would bevery useful for implementation of control measures In 2002 bark chips fromThompson navel and Sanguinella sweet orange trees grafted on P trifoliata rootstockswith exocortis symptoms were budded on Etrog citron Arizona 861 S1 seedlings andmaintained in the greenhouse at 25 30 C After 6 months the inoculated citron plantsshowed variable Mild to severe symptoms Ribonucleic acids were extracted fromyoung symptomatic leaves and subjected to Reverse transcription polymerase chainreaction using specific primer pairs for Citrus exocortis viroid CEVd Amplifiedproducts were analysed through electrophoresis on 2 agarose gels Although somesamples didn t show any relevant DNA band most did The CEVd DNA bands werepurified using High Pure PCR Product Purification Kit Roch Germany and subjectedto Single strand conformation polymorphism SSCP analysis Five samples from eachof the 5 different isolates which had different SSCP pattern were cloned in pBluescript SK At least one clone of each of the five CEVd isolates were sequenced in both directions Alignment of the nucleotide sequences by BLASTn NCBI program revealed markedidentity with other CEVd isolates deposited in GenBank A further study wasundertaken to recognize the nature of the variation observed for exocortis likesymptoms amid the fact that CEVd was not found in some of the samples RT PCRwas performed using specific primer pairs for Citrus bent leaf viroid Citrus viroid OS Citrus viroid I LSS Hop stunt viroid Citrus viroid III and Citrus viroid IV PCRproducts were electrophoresed on 2 agarose gels and sequenced Sequence analysis byBLASTn NCBI revealed the presence of the citrus viroids in these samples Becausethe presence of these citrus viroids in these samples was confirmed via sequenceanalysis the variability in the exocortis like symptoms in the inoculated Etrog citroncould be the result of differences in the number of viroid species present in infectedcitrus trees in the north of Iran Uniplex RT PCR Multiplex RT PCR and Dot blotassays using Digoxigenin labled RNA probe were compared for their comparativecapabilities in detection of CEVd Among these assays Uniplex RT PCR proved to bethe most sensitive method in identification of CEVd This is the first report of citrusinfection by the several citrus viroids in Iran

علي آهون منش ، هاله هاشمي سهي

حشمت اله رحيميان

امير مساح، رضا زارعي