| Heilongjiang and Yunnan are two main provinces in China where pumpkin growing namely, the former cultivates during spring, while the later cultivates all over the year. In recent years, with the continuous expansion of cultivating, virus diseases became more serious, causing enormous losses in yield and quality. The main viruses in pumpkin diseased samples from Heilongjiang and Yunan were identified and their coat protein (CP) genes were cloned and the pumpkin germplasm from Heilongjiang and Yunnan provinces were screened for resistance to those viruses,which will be a basis of breeding for resistance to virus diseases and also for the prevention and control of the virus diseases in pumpkin191 pumpkin diseased samples were collected from the main cultivating areas of Heilongjiang Province (149 samples) and Yunnan Province (42 samples). The morphological and cytopathological characters of the viruses were observed by electron microscopy(EM) The types of virus were identified with I-ELISA, DAS-ELISA, TAS-ELISA, RT-PCR and IC-PCR. The CP genes of the main viruses identified in this research were amplified by PCR, cloned into pGEM-T and sequenced. The pumpkin germplasm from Heilongjiang and Yunnan provinces was screened for resistance to the main viruses using friction and roots immersed inoculation.PRSV-W,CMV,ZYMV and WTG were found in pumpkin from Yunan,and their inflecting proportion were 52.4%,38.1%,11.9% and 2.4% respectively. WMV and CMV were found in pumpkin from Heilongjiang, their inflecting proportion were 24.2% and 17.5% respectively. Tospovirus particles could be observed clearly by EM both in pumpkin diseased samples from Yunnan and Heilongjiang provinces. Viruses could be co-inflected pumpkin under the natural condition. The result showed that PRSV-W and CMV were main viruses in Yunnan , but the main viruses in Heilongjiang were CMV and WMV.Cytopathological study on leaves of pumpkin infected with PRSV-W, WMV showed that there were large amount of inclusion in shape of pinwheel, lamina, and braid in the cells, and there were many linear virus particles fascicled or scattered in the cytoplasm, causing the cytopathological characters which was similar to typical potato virus Y (potyvirus). Virus particles assemble inside the globular shape membrane in the cytoplasm of pumpkin infected with CMV. There were no other reports on cytopathological research on virus disease ofpumpkin in China until now.The sequencing results showed that CP genes of PRSV-W isolates from Menzi (PRSV-MZ) and Shiping(PRSV-SP) in Yunnan had 873bp,coding for 291 amino acids, but the those from Eshan(PRSV-ES), Banna(PRSV-BN) and Bingchuan(PRSV-BC) were 867bp, coding for 289 amino acids. The CP genes of PRSV-MZ and PRSV-SP shared a homology of 98.75% in nucleotide sequence and 98.90% in amino acid. Compared with PRSV 17 sequences abroad and 2 sequences in China, the results showed that there were little difference between CP gene sequences of PRSV-W and PRSV-P, which was related to the geographical position.The sequencing result showed that CP gene of WMV isolate from Heilongjiang (WMV-HLJ) had 852 bp, coding for 284 amino acids. The results of sequencing and restrction analysis showed that homology of CP genes of WMV isolates from Heilongjiang and Shanxi was higher than that from Zhengzhou.The sequencing analysis of CP genes of CMV isolates from Yunnan (CMV-YN)and Heilongjiang(CMV-HLJ)showed that their CMV CP genes had 657 bp, coding for 219 amino acids. The CP genes of CMV-YN and CMV-HLJ shared a homology 96.8% in nucleotide sequence and 97.4% in amino acid. The homology of nucleotide sequence and amino acid between these two isolates and different isolates from abroad and China in subgroup I were higher than 89% and 93% respectively, but those between these two isolates and different isolates from abroad and China in subgroup II were lower than 69% and 71% respectively. This result showed that CMV isolates from Yunnan and Heilongjiang belonged to CMV subgroup I.11 pumpkin cultivars/lines from Yunnan were screene...
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