| White-blacked planthopper (WBP), S. furcifera is an important vector of Southern rice black-streaked dwarf virus (SRBSDV), and it is very important to determine transmission character and transmission efficiency the vector to transmitting SRBSDV for elucidation of epidemic regularity of this viral disease and establishment of the controlling methods. The results were as follows:1Transmission character of the vector WBPThe acquisition access period of the vector at the different development stage (e.g. the first instar nymphae, the third instar nymphae, the fifth instar nymphae, macropter and brachypter) were11-19min,6-12min,3-9min,2-8min and2-8min, respectively. At26℃, the circulative period of SRBSDV in the body of the vector at different development life stage (e.g. the first instar nymphae, the third instar nymphae, the fifth instar nymphae, macropter and brachypter) was7-11d,5-8d,3-7d,4-8d and3-6d, respectively. The shortest inoculative access periods of rice seedlings at the three-leaf stage by the SRBSDV-infected vector (e.g. the fifth instar nymphae, macropter and brachypter) was4min,5min and6min respectively while the longest inoculative access periods were8min,10min, and11min, respectively. The shortest inoculative period on rice seedlings at the early tillering stage by the SRBSDV-infected vectors including the fifth instar nymphae, macropter and brachypter was5min,7min and7min, while the longest time were10min,12min and12min, respectively. Once WBP is infected with virus, it will have the life-long capacity to transmit the virus, but it can not transmit virus through its egg. The maximum number of rice plants infected with SRBSDV by single WBP was87and the average was48.3±0.8.2Efficiency of the vector WBP to transmit SRBSDV among various species of host plantsSeven species of plants, rice plant, Echinochloa crusgalli, Zea mays, Paspalum distichum, Alopecurus aequali, Juncellus serotinus and Cyperus difformis, had been the host plants of SRBSDV in the rice fields and/or adjacent to the rice fields. The vector could had transmitted the virus among rice plants, E. crusgalli, Z. mays, P. distichum and A. aequali at the interspecific level, could had transmitted the virus among rice plants, E. crusgalli and Z. mays at the intraspecific level, could had transmitted the virus between P. distichum and E. crusgalli, and between P. distichum and A. aequali, couldn't transmit the virus between these plants in the family Gramineae and those plants in the family Cyperaceeae, and also couldn't transmit the virus between J. serotinus and C. difformis at the interspecific and instraspecific level. At15℃,20℃,25℃,30℃and35℃, the macropterous and brachypterous adult of S.furcifera could transmit SRBSDV from these plants (e.g. E. crusgalli, Z. mays and rice plants) infected with SRBSDV to the rice seedlings. As the temperature rises, its transmission efficiency first rises and then falls down, and it reach the peak at25℃. When the vector brachypter transmitted SRBSDV from E. crusgalli, Z. may and rice plants to rice seedlings, the respective rate of the rice seedlings infected with the virus at15℃was21.7%,13.8%and18.3%, the corresponding rate of rice seedlings infected with the virus at25℃was37.3%,48.6%and42.8%, and the rate of rice seedlings infected with the virus-at35℃Cwas17.4%,13.4%and10.2%, respectively. When the vector macropter transmitted SRBSDV from E. crusgalli, Z. may and rice plants to rice seedlings, the respective rate of the rice seedlings infected with the virus at15℃was26.2%,18.8%and23.7%, the corresponding rate of rice seedlings infected with the virus at25℃was56.6%,64.6%and53.6%, and the rate of rice seedlings infected with the virus at35℃was11.2%,10.2%and7.3%, respectively. Transmission efficiency of the brachypterous adults was higher than that of the macropterous adults at15℃,20℃and25℃, while at35℃transmission efficiency of the brachypterous adults was less than that of the macropterous (P<0.05). So S. furcifera can transmit SRBSDV among various species of plants in the family Cyperaceeae as mentioned above, ability of the vector to transmit SRBSDV was markably affected by temperature, at25℃transmission efficiency of the vector reached to the max., and ability of the brachypterous adults to transmit SRBSDV more than that of the macropterous adults above30℃.3Efficiency of the vector WBP to transmit SRBSDV in different factorsThe fifth instar nymph, macropter and brachypter could transmit SRBSDV among rice plants at different growth stage under the temperature range from18℃to34℃, and the transmission efficiency was from3.3%to41.2%. Transmission efficiency was affecting significantly by vector life stage, temperature, and rice growth stages (P<0.01), transmitting capacity of the vector in order was the fifth instar nymph> brachypter> macropter, transmission efficiency of WBP reached the maximum value at26℃, and then declined in turn at22℃,28℃,18℃and34℃, and infection rate of rice plants by the vector was declined with the plants being growing. Any two of three factors (e.g. vector life stage, temperature and rice growth stages) presented noted interaction effect on WBP to transmitting SRBSDV (P<0.01), the importance of these factors in order was temperature> rice growth stage> vector life stage> temperature×vector life stage> temperature×rice growth stage> vector life stage×rice growth stage. Five rice varieties exhibited different SRBSDV-infected rate, with the respective infection rate being41.7%on Lingliangyou,37.6%on Jinyou899,36.2%on Jinyou284,32.1%on Peiliangyou981, and29.3%on Weiyou644. Infection rate on Lingliangyou was remarkably higher than that of the other varieties (P<0.05), there was no significant difference between infected-rate on Jinyou899and that on Jinyou284(P<0.05), SRBSDV-infected rate on Weiyou644was lower than that of any other varieties (P<0.05). When fasting period was above12-hours, capacity of the macropter to transmit SRBSDV markedly declined (P<0.05). |
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