| Apple chlorotic leaf spot virus (ACLSV) and Apple stem grooving virus (ASGV) worldwidely infect apple, pear and many stone fruit trees. ACLSV and ASGV are the members of genus Trichovirus and Capillovirus, respectively. Xinjiang province has unique geographic conditions and long history for fruit production. There are a lot of local fruit germplasm with excellent features. Pyrus sinkiangensis is a special pear breed. In order to know the virus infection status of pears and apples in Xinjiang, ACLSV and ASGV in pears and apples from Xinjiang were detected by biological and molecular methods and their molecular characteristics were analysized. The results were described as followings.Fourty samples were collected from Korla pear, New pear no.7, Dangshan pear,Bartlett and Red Fuji apple. The crude extracts from young leaves of these samples were mechanically inoculated onto Chenopodium quinoa. The results showed that 16 samples induced symptoms, including chlorotic spots, necrotic spot and crinkle, on inoculated Ch. quinoa plants. The ACLSV and ASGV infection in these plants were tested by tube capture reverse transcription-polymerase chain reaction (TC-RT-PCR) and immunity capture reverse transcription-polymerase chain reaction (IC-RT-PCR). The results revealed that four samples were ACLSV positive and six were ASGV.The total RNAs were extracted from young leaves of different samples and used as the templates for amplification of the fragment near 3'-terminal genome of ACLSV by RT-PCR. The products with a expected size about 680 bp were amplified from eight samples. The products were cloned. One positive clone from each isolate was sequenced. Results showed that the sizes of these cloned fragments were 680bp-703bp, which included 3'-terminal of CP gene (506nt, accounting for 87% of the complete CP gene of 582 nt) and partial 3'-terminal no-coding region sequences.The cloned fragments of ACLSV from Korla pear (KI-2), New pear no.7 (XI-1) and Red Fuji apple(AFI-4) were analyzed by single strand conformation polymorphism (SSCP). The clones from each sample showed different SSCP types were sequenced. Sequence alignment analysis showed that these three isolates had different divergency levels. Three molecular variants (KI-2-6, KI-2-17 and KI-2-23) from Korla pear(KI-2) showed high molecular divergence, sharing similarities of 84.8-85.4%. Two molecular variants (XI-1-3 and XI-1-17) from New pear no.7(XI-1) and three molecular variants (API-4-4, API-4-21 and API-4-34) from Red Fuji apple (API-4) had high similarities of 99.8% and 92.5-99.8%, respectively.The phylogenetic tree was constructed based on nucleotide sequences of CP gene of detected ACLSV molecular variants and reference isolates. Results showed that seven molecular variants had lower genetic distances and clustered into a group with a isolate "kuerle", early reported from China, and an apple isolate P205 from Japan. Another molecular variants ACLSV-KI-2-6 was closer to an apple isolate ACLSV-C reported from China and they formed another group with some ACLSV isolates from stone fruit trees.No-coding region near the 3'end of ACLSV genome showed high variabilities among eight molecular variants from three isolates with the similarities ranging 80.6-100%. The results of nucleotide acid sequence alignment showd several gaps in some sequences, which contributed for the size differences of cloned fragments.The ASGV products with a expected size about 500 bp were amplified from 10 pear samples from XinJiang,2 samples of Pyrus pyrifolia and 3 Red pear samples from YunNan province by RT-PCR. All these amplified products were cloned and sequenced. Comparison of these sequences showed that the CP gene from these isolates shared similarities ranging 88.2-100%(nt) and 95.6-100%(aa), respectively. The CP gene of ASGV from P. sinkiangensis shared similarities ranging 88.2-99%(nt) and 95.6-99%(aa) with that from Red pear, and 89.8-97.1%(nt),96.9-99.4%(aa) with that from P. pyrifolia.
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