中文摘要：

为了研究旱地马铃薯脱毒种薯退化原因，对不同脱毒级别的种薯进行病毒检测，播种后统计田间发病情况。结果表明，随着脱毒种薯脱毒级别的升高，种薯侵染的病毒种类明显增加，‘陇薯3号’原原种仅被2种病毒（PLRV和PVX）侵染，原种、一级种和二级种都被4种病毒（PLRV、PVX、PVS和PVM）侵染；‘陇薯6号’原原种未被病毒侵染，原种和一级种各被1种病毒（PLRV或PVX）侵染，二级种被2种病毒（PLRV和PVS）侵染，‘陇薯3号’抗病毒弱，较‘陇薯6号’易被病毒侵染。种薯播种出苗后，卷叶病和花叶病的发病率和病情指数随着种薯脱毒级别的升高而显著升高。随着马铃薯种薯脱毒级别的升高，收获后马铃薯腐烂率显著增大，商品薯率有降低趋势。除原原种外，马铃薯的产量随种薯脱毒级别的升高而显著降低，‘陇薯3号’和‘陇薯6号’的产量由高到低的顺序依次为原种〉一级种〉二级种〉原原种。

英文摘要：

For the purpose of investigating the reasons of virus-free seed potato degradation, the viruses of virus-free seed potatoes in different grades were detected, and the occurrence of virus diseases on plants grown from different grades of seeds was recorded. The results showed that the amount of the virus species that infected seed potatoes significantly increased with the virus-free seed grade increasing. ‘Longshu 3＇ pre-elite was only infected by two viruses （PLRV and PVX）. ‘Longshu 3＇ elite, certified I and 1[ seeds were infected by four viruses （PLRV, PVX, PVS and PVM）. ‘Longshu 6＇ pre-elite was not infected by viruses. ‘Longshu 6＇ elite and certified I seeds were both infected by one virus （PLRV or PVX）. ‘Longshu 6＇ certified II seeds were infected by two viruses （PLRV and PVS）. ‘Longshu 3＇ was easier to be infected by virus than ‘Longshu 6＇. When potato seeds germinated, the disease incidence and index of leaf roll and mosaic had significantly raised with the virus-free seed grade increasing. In addition, potato rotting rate had significantly increased, and marketable potato percentage had showed decreasing trend with the virus-free seed grade increasing. Except for pre-elite seeds, other potato yields decreased as the virus-free seed grade increasing. The order of ‘Longshu 3＇ and ‘Longshu 6＇ yields from high to low was elite seeds, certified I, certified II and pre-elite.