烟草丛顶病研究进展

 烟草丛顶病是一类在局部地区产生严重危害的烟草病害,由烟草丛顶病毒和烟草扭脉病毒复合侵染引起。目前该病在我国仅云南有发生的报道,烟草丛顶病也是国内第一个报道的由幽影病毒属成员引起的病害。本文较为系统全面地综述了烟草丛顶病的发生与分布、病害症状学、病原物、与病害相关的dsRNA、病组织超微病变以及病害的流行及控制等方面的研究进展。     

Movement of aphid-transmitted Sugarcane yellow leaf virus (ScYLV) within and between sugarcane plants

Sugarcane yellow leaf virus (ScYLV) is distributed worldwide and has been shown to be the cause of the disease sugarcane yellow leaf syndrome (YLS). This study was an investigation of the transmission and spread of ScYLV in Hawaii. Several aphids are known to transmit the virus, but investigation of infestation and transmission efficiency showed Melanaphis sacchari to be the only vector important for field spread of the disease. The initial multiplication of ScYLV in a virus-free plant occurred exclusively in very young sink tissues. When a single leaf was inoculated on a plant, that leaf and all older leaves remained virus-free, based on tissue-blot immunoassay, whereas meristems and all subsequently formed new leaves became infected. Therefore, only after those leaves which had already developed before inoculation had been shed, did the complete plant contain ScYLV. Spread of the viral infection to neighbouring plants in the plantation fields via aphids was relatively slow and in the range of a few metres per year. No indication of long-distance transfer could be seen. This indicates that it may be possible to produce and use virus-free seed cane for planting of high-yielding but YLS-susceptible cultivars.     

The recombinant isolate of cucurbit aphid-borne yellows virus from Brazil is a polerovirus transmitted by whiteflies

The severe yellowing disease (amarelão) on melon plants is a serious problem in Brazil, although the causative agent remained unknown for a long time. Recently, recombinant isolates of cucurbit aphid-borne yellows virus (CABYV) were reported as the possible causative agents of this disease on melon plants. Although aphids are known to be the vectors of the common type of CABYV isolates, almost no aphid colony was observed in the major melon fields in Brazil with high incidence of the severe yellowing disease. In contrast, whiteflies are often abundant. Based on this observation, the hypothesis of the transmission of recombinant CABYV by whiteflies was evaluated. After thorough transmission experiments, we found that this recombinant CABYV isolate was transmitted by the whitefly Bemisia tabaci MEAM1, but not by Aphis gossipii. Furthermore, the host response by whitefly-based inoculation in cucurbits and other indicator plants showed differences in host range when compared to the common type of CABYV. Due to its transmissibility by the whitefly and the distant relationship of the P3/P5 protein to CABYV, the name “cucurbit whitefly-borne yellows virus” is proposed for this recombinant CABYV. This is the second report of polerovirus transmission by the whitefly B. tabaci, following the report of pepper whitefly-borne vein yellows virus.