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Authors requiring further information regarding Elsevier’s archiving and manuscript policies are encouraged to visit: http://www.elsevier.com/copyright Author's personal copy Crop Protection 41 (2012) 71e76 Contents lists available at SciVerse ScienceDirect Crop Protection journal homepage: www.elsevier.com/locate/cropro Transmission characteristics of Southern rice black-streaked dwarf virus by rice planthoppers Lingling Pu, Guohua Xie, Chunyan Ji, Bing Ling, Maoxin Zhang, Donglin Xu, Guohui Zhou* College of Natural Resources and Environment, South China Agricultural University, Wushan, Tianhe District, Guangzhou, Guangdong 510642, China article info abstract Article history: Southern rice black-streaked dwarf virus (SRBSDV) is a recently proposed distinct species in the genus Received 23 November 2011 Fijivirus, family Reoviridae. During the past decade, SRBSDV has spread throughout southern China and Received in revised form northern Vietnam, and has become one of the greatest threats to rice production in these regions. 17 April 2012 We evaluated three common planthopper species affecting rice: white-backed planthopper (WBPH, Accepted 22 April 2012 Sogatella furcifera), brown planthopper (BPH, Nilaparvata lugens) and small brown planthopper (SBPH, Laodelphax striatellus) to determine their virus transmission abilities. It was confirmed that WBPH was an Keywords: efficient persistent-transmitting vector for SRBSDV. Neither BPH nor SBPH were viral vectors, although Southern rice black-streaked dwarf virus Brown planthopper a small proportion (3.7%) of tested SBPH acquired the virus from diseased rice. We characterized the Small brown planthopper virus transmission properties of WBPH. 83% of the tested insects fed on virus-infected rice plants became White-backed planthopper viruliferous. The minimum virus acquisition and inoculation access periods were 5 and 30 min, respectively, for both WBPH nymphs and adults. The circulative transmission periods of the virus in WBPH ranged from 6 to 14 days, and most viruliferous individuals transmitted the virus in intermittent periods ranging from 2 to 6 days. A single individual of WBPH could infect 8e25 rice plants with the virus in a 5-day period. WBPH could transmit SRBSDV from rice to maize seedlings, but it was barely able to acquire the virus from infected maize. These results improve our understanding of the epidemiology of SRBSDV, and will be useful for development of disease control strategies. Ó 2012 Elsevier Ltd. All rights reserved. 1. Introduction Research Institute, personal communication). According to our previous study (Zhou et al., 2008), SRBSDV can be transmitted A new rice dwarf disease caused by Southern rice black-streaked efficiently by white-backed planthopper (WBPH, Sogatella furci- dwarf virus (SRBSDV), a recently proposed novel species in the fera). The small brown planthopper (SBPH, Laodelphax striatellus) genus Fijivirus, family Reoviridae, was first discovered in Guang- transmits SRBSDV only under experimental conditions with a rela- dong Province, China, in 2001 (Zhang et al., 2008; Zhou et al., 2008; tively low efficiency. However, few studies have been conducted on Wang et al., 2010a). In the past decade, the disease has rapidly the transmission properties of the virus by rice planthoppers. spread throughout southern China and northern Vietnam, and A better understanding of the vectoreSRBSDVehost interaction SRBSDV has become one of the most important rice pathogens in system is important for control of the disease. these regions (Guo et al., 2010; Hoang et al., 2011). The virus infects The genus Fijivirus includes eight recognized species: Fiji disease a group of Poaceae species including rice, maize, Chinese sorghum virus (FDV), Oat sterile dwarf virus (OSDV), Garlic dwarf virus (GDV), (Coix lacryma-jobi), Echinochloa crusgalli, and Pennisetum flaccidum Nilaparvata lugens reovirus (NLRV), Mal de Rio Cuarto virus (MRCV), (Zhou et al., 2008). In 2009, it was estimated that up to 315,000 ha Pangola stunt virus (PaSV), Maize rough dwarf virus (MRDV), and Rice of rice growing in nine Chinese provinces were infected, and more black-streaked dwarf virus (RBSDV). Except for GDV, whose vector is than 6500 ha of rice crops were completely destroyed. In 2010, still unknown, all fijiviruses propagate in vivo in their hopper SRBSDV infection had spread to 13 provinces in southern China, 28 vectors in a persistent manner (Milne et al., 2005). These viruses in northern Vietnam and one in central Vietnam, with 1,601,600 ha move from the gut lumen to hemolymph or other organs in their of rice infected (Guo et al., 2010). Recently, the virus has been vectors, and finally enter the salivary glands, from which they are detected in Japan and Korea (Heong K.L., International Rice inoculated into plant hosts by the vectors during feeding (Gray and Banerjee, 1999). The planthopper vectors of fijiviruses belong to * Corresponding author. Tel.: þ86 20 85280306. several genera in the Delphacidae family: the genus Perkinsiella for E-mail address: [email protected] (G. Zhou). FDV, Javesella for OSDV, Delphacodes for MRCV, Laodelphax for 0261-2194/$ e see front matter Ó 2012 Elsevier Ltd. All rights reserved. doi:10.1016/j.cropro.2012.04.026 Author's personal copy 72 L. Pu et al. / Crop Protection 41 (2012) 71e76 RBSDV and MRDV and Sogatella for PaSV. Under experimental 2.5. Acquisition access period (AAP) of WBPH conditions, fijiviruses can be transmitted by some other plan- thoppers at low efficiency (Milne et al., 2005). NLRV propagates in The 3rde4th instar WBPH nymphs were collected from infected brown planthopper (BPH, Nilaparvata lugens) but not in rice, the rice plants and transferred to virus-free rice seedlings at the 2e3-leaf only host plant of BPH, and only NLRV among the fijiviruses can be stage (two or three insects per plant) in glass culture tubes. The insects transmitted via eggs (Nakashima and Noda, 1995). Previous data were killed 24 h later. RT-PCR detectionwas conducted at 10 days post have revealed that SRBSDV is transmitted by WBPH at a high rate inoculation (dpi), and the seedlings positive with the virus were used and by SBPH at a relatively low rate. The virus does not appear to be for the following tests. transmitted by BPH or seeds (Zhou et al., 2008; Wang et al., 2010b). The non-viruliferous 3rde4th instar WBPH nymphs starved for In this study, we investigated the transmission of SRBSDV by 1e2 h were transferred to the SRBSDV-infected rice seedlings. The three potential vectors, WBPH, BPH and SBPH under artificial nymphs fed for 5, 10, or 30 min or 3 or 24 h were respectively conditions. We determined the transmission characteristics of transferred to virus-free rice seedlings at the 3-leaf stage in glass SRBSDV by WBPH in rice and maize. The results improve our culture tubes (one insect per tube). The seedlings inoculated with understanding of the epidemiology of SRBSDV, and will ultimately nymphs were maintained for 15 days at 27 C, relative humidity of be useful for development of disease control strategies. 60e75%, under a 16-h light/8-h dark photoperiod. The insects still alive at 15 dpi were collected and tested for the 2. Materials and methods presence of the virus by RT-PCR. The AAP of WBPH was calculated from the RT-PCR results. 2.1. Tested host plants and planthopper species 2.6. Inoculation access period (IAP) of WBPH The seeds of rice (cultivar “Qiuyou 998”) and maize (cultivar “ ” super sweet ) were purchased from the Guangdong Academy of The second-generation WBPH nymphs of 3rde4th instar or Agricultural Sciences, China, and sown in pots. The plants were adults propagated on infected rice plants were collected and maintained in insect-proof cages under greenhouse conditions at starved for 2 h, then transferred to the virus-free rice seedlings at e 20 28 C. Non-viruliferous individuals of WBPH and BPH were 2e3-leaf stage. The insects were allowed to feed on the seedlings fi collected from rice elds in Guangzhou, Guangdong Province, for 5, 10 and 30 min and 3, 12 and 24 h respectively, and individ- China, and SBPH was kindly provided by Dr. Yijun Zhou (Jiangsu ually detected by RT-PCR to confirm whether they were viruliferous Academy of Agricultural Sciences, Nanjing, Jiangsu Province, or not. The seedlings inoculated with confirmed viruliferous WBPH China). The three species of planthoppers were separately main- were grown for 15 days under the conditions described above. e tained in insect-proof cages at 26 28 C and relative humidity of The IAP of WBPH was determined from the results of RT-PCR e 60 75%. Adult male or female hoppers were transferred to new detection of the tested plants at 15 dpi. cages with healthy rice seedlings when the plants they fed came to late growth stage, and the insects were allowed to propagate for 2e3 generations before being used. 2.7. Circulative transmission period of SRBSDV in WBPH Thirty nymphs at the 3rde4th instar stage were fed on infected 2.2. Virus resource rice plants for 24 h and transferred to virus-free rice seedlings in glass culture tubes (one plant per tube). The tested plants were SRBSDV was obtained from infected rice field samples in replaced by healthy ones every two days until the insects died.