| Potato is one of the important economic crops in XinJiang. Potato production was affected seriously by occasion of endemic phenomena on potato yellow dwarf in Production. For understanding its disease and damage, Potato yellow dwarf disease was investigated from the main potato croplands in north regions of Xinjiang (including Urumqi Xishan farm, Shawan, Qitai , Manas , Karamay , Kuitun , Altai ,Yili , Tacheng) during 2006-2007. The infection induces typical dwarfism symptoms of plant accompanied with apical cluster as well as yellow leaf from new to old, and smaller whereas light of diseased potato tuber which becomes surface chapping or uneven, resulting in the degeneration and reduction of tuber. The results showed the incidence rate of the disease is 22%-80%, and the disease index is 0.19-27.56. Besides, Investigation show that the virus disease incidence of potato yellow dwarf disease is connected with to cultivating measures.Meanwhile, the damage degree of potato yellow dwarf disease was understood and damage expectancy was made by what is analyzing the incidence of the disease and potato output in recent three years.PV-1 isolate was obtained from naturally infected potatao with symptoms of yellowing and dwarf in Yili and QiTai of northern Xinjiang, and was identified as the Potato leaf roll virus by RT-PCR amplification. PV-2 isolate was obtained throught three times of single spot isolation on chenopodium quinoa that was inoculated by disease sample from Urumqi Xishan,Yili and Altai of north regions of Xinjiang Tianshan, and was identified as PSTVd by symptoms on the test plants and RT-PCR amplification. PV-3 was obtained from Nicotianal rustica L after inoculating and the triple single spot separating that was inoculated disease sample form Urumqi Xishan, Qitai Yili and Tacheng basin of north regions of Xinjiang Tianshan, and was doubted identified as PSTVd by symptoms on the test plants,it still remains unclear. The correlation protein gene of PV-1 and PV-2 isolate was amplified from the extracted plant total RNA by using RT-PCR, and cloned into the pMD20-T vector and sequenced. From results, The cloned segment is 639 bps nucleotides and encodes 212 amino acid residues from virus isolate PV-1. Comparison of the nucleotide and amino acid sequences of the full length of CP gene of isolate PV-1 with the corresponding sequences of 19 the Potato leaf roll virus isolates reported showed that the homology are 95.03%—98.80% at nucleotide level , and 97.12 %—100 % at amino acid level ,respectively. Therefore, PV-1 isolate was identified as Potato leaf roll virus. the cloned segment was 363bp gene is coded a part of RNA correlation gene from PV-2 isolate. Comparison of the nucleotide of PV-2 isolates with various countries in the world the corresponding sequences of the part of the PSTVd isolates reported showed that the homology are 92.2 %～99.8 % at nucleotide level , respectively. Therefore, PV-2 isolate was identified as Poato spindle tuber viroid.Detection of causal virus species was carried out by multiple RT-PCR for potato yellow and dwarf virus disease in northern Xinjiang. The detection results indicated that in detection of 700 disease sample of potato planting areas in northern Xinjiang, PVY was the most common virus and infectious frequencies was 32.28%, and the infectious frequencies by PVX ,PVS,PSTVd,PLRV and PVA were 18.92%,17.07%,15.03%,8.53%,8.16%, respectively. the complex infection of Potato virus were 23%.
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