ISHS Acta Horticulturae 386: XVI International Symposium on Fruit Tree Virus diseases
NUCLEOTIDE SEQUENCE AND SECONDARY STRUCTURE OF POME FRUIT VIROIDS FROM DAPPLE APPLE DISEASED APPLES, PEAR RUSTY SKIN DISEASED PEARS AND APPLE SCAR SKIN SYMPTOMLESS PEARS |
| Authors: | S.F. Zhu, A. Hadidi, X. Yang, R.W. Hammond, A.J. Hansen |
| Abstract:
Dapple apple viroid (DAVd) and pear rusty skin viroid (PRSVd) are members of the apple scar skin viroid (ASSVd) group. In order to study the degree of structural variation among DAVd, PRSVd, and ASSVd, each viroid was reverse transcribed in total nucleic acids from infected tissue and then amplified by polymerase chain reaction using ASSVd-specific primers. Gel-purified RT-PCR product of each viroid was directly sequenced or cloned into the vector pUC18 or pCRII, then sequenced. ASSVd from symptomless pears is 330 nucleotides in length and its sequence is almost identical to that of the prototype 330 nucleotides Japanese isolate of ASSVd from apples. DAVd from diseased apples is 331 nucleotides in length and is 97% homologous to ASSVd. PRSVd consists of 334 nucleotides and shares 92% homology with ASSVd. The sequence of each viroid can be arranged into viroid-specific rod-like structure. DAVd and PRSVd differ from the prototype isolate of ASSVd at 9 sites and 25 sites, respectively. Most of the changes in DAVd and PRSVd occur in regions corresponding to the pathogenicity and left terminal domains of ASSVd which are believed to control viroid pathogenicity. | |
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