Simulation modelling of potato virus Y spread in relation to initial inoculum and vector activity

Potato virus Y(PVY)is a non-persistent virus that is transmitted by many aphid species and causes significant damage to potato production.We constructed a spatially-explicit model simulating PVY spread in a potato field and used it to investigate possible effects of transmission efficiency,initial inoculum levels,vector behavior,vector abundance,and timing of peak vector activity on PVY incidence at the end of a simulated growing season.Lower PVY incidence in planted seed resulted in lower virus infection at the end of the season.However,when populations of efficient PVY vectors were high,significant PVY spread occurred even when initial virus inoculum was low.Non-colonizing aphids were more important for PVY spread compared to colonizing aphids,particularly at high densities.An early-season peak in the numbers of noncolonizing aphids resulted in the highest number of infected plants in the end of the season,while mid-and late-season peaks caused relatively little virus spread.Our results highlight the importance of integrating different techniques to prevent the number of PVY-infected plants from exceeding economically acceptable levels instead of trying to control aphids within potato fields.Such management plans should be implemented very early in a growing season.

Screening and Identification of Tobacco Mutants Resistant to Potato Virus Y( PVY)

[ Objective] This study aimed to screen and identify tobacco mutants resistant to potato virus Y （PVY）, thus laying the foundation for obtaining PVY resistance genes. [ Method ] At seedling stage, tobacco mutant materials were inoculated with PVY virus and preliminarily screened by naked-eye observation. Enzyme-linked immunosorbent assay （ELISA）, real-time fluorescence quantitative PCR and test strip assay were performed to further identify the pre-screened PVY- resistant seedlings. [ Result ] In 2011, two highly PVY-resistant tobacco mutants （MZE2-15 and MZE2-16） and three PVY-tolerant mutants （MZE2-70, MZE2- 207 and MZE2-228） were obtained, which were further screened and identified in 2012. According to the results, tobacco mutant materials MZE2-407 and MZE2- 428 were susceptible to PVY; mutant materials MZE2-16 and MZE2-15 were resistant to PVY. [ Conclusion] This study provide theoretical basis for the control of tobacco PVY disease.

Effects of Synergism Between PVY and PVX on Virus Titer and Cell Ultrastructure in Tobacco Plants

The viruses titer and the ultrastructure of infected cells in tobacco host (Nicotiana tabacum cv. Samsun), which doubly infected with potato virus Y necrosis strain (PVYN) and potato virus X (PVX), were studied under greenhouse conditions. The results indicated that PVYN and PVX interacted synergistically. and tobacco plants which doubly infected with PVX and PVYN could greatly increase symptom severity as compared with that induced by the single virus. As determined by triple antibody sandwich enzyme-linked immunosor-bent assay (TAS-ELISA), the titer of PVX in the tobacco leaves infected with both PVYN and PVX was up to 9.10 times higher than the plants infected with PVX only. No significant differences in PVYN titer were detected between singly and doubly infected plants. The enhancement of PVX titer in doubly infected plants was evident in greenhouse and was independent of the virus strains, tested seasons, intervals between PVYN and PVX inoculation. When sections of doubly infected leaves were examined with an electron microscope, it could be frequently found that cells contained pinwheels and large masses of PVX-like particles, pinwheels and laminate inclusions, or all three structures, most of them were swollen, and their chloroplast and other organella were destructed heavily. This suggested that doubly infected cells were involved in the enhancement phenomenon, which seemed to be the result of an increase in the amount of PVX synthesized in them.

青海省部分地区马铃薯病毒种类与Y病毒株系类型研究

【目的】了解马铃薯主要病毒对青海省部分地区马铃薯生产的危害,明确青海省部分马铃薯产区主要病毒类型及PVY株系类别,对马铃薯病毒病的防治和品种选育工作提供科学依据。【方法】利用DAS-ELISA和RT-PCR结合生物信息学分析方法对采自青海省大通县和互助县的181份疑似马铃薯病毒病样品进行病毒种类检测和Y病毒株系类型分析。【结果】181份样品中,PVY、PVS、PVM和PLRV病毒的检出率分别为17.68%、19.34%、4.42%和4.42%,其中,PVY单独侵染率最高,达14.92%,其次PVS为12.71%,样品中未检出PVX、PVA和AMV病毒。复合侵染中以2种病毒复合侵染为主,其中PVS+PVM、PVY+PVS和PVS+PLRV发生情况较为常见。DAS-ELISA检测PVY单独侵染结合RT-PCR混检获得20份PVY阳性样品,对其进行马铃薯Y病毒株系血清学检测分析发现,青海省部分地区马铃薯Y病毒株系以PVY^(O+C)血清型为主,其中PVY^(O+C)血清型阳性株系19份,占比为95%,PVY^(N)与PVY^(C)血清型阳性株系各1份,均占比为5%。为进一步明确PVY亚株系,根据血清学检测结果,对获得的19个PVY分离物的基因序列进行分析,发现PVY病毒核苷酸一致率为97.0%~100%,氨基酸一致率为95.8%~100%,且未发现重组位点,种群基因较稳定,PVY分离物系统发育分析发现,16个PVY分离物与PVY^(N:O)株系亲缘关系较近,3个PVY分离物PVY^(NTN-NW)株系亲缘关系较近,青海省部分地区马铃薯Y病毒株系类型以PVY^(N:O)、PVY^(NTN-NW)株系为主,与血清学检测结果一致。【结论】青海省部分地区主要马铃薯病毒种类有PVY、PVS、PVM和PLRV,PVY和PVS是青海地区马铃薯病毒的主要流行种类,其中Y病毒株系类型以PVY^(N:O)和PVY^(NTN-NW)株系为主,且同源性很高,PVY的种群基因较稳定。