Tracking The Source Regions Of Southern Rice Black-Streaked Dwarf Virus Transmitted By Sogatella Furcifera (Horváth) In Zhejiang, Jiangxi And Anhui

The southern rice black-streaked dwarf virus (SRBSDV) is a new species of the Fijivirus in Reoviridae, which was first observed in Yangxi county, Guangdong province,2001, and spread widely in the north of Vietnam and the southern rice yield of China recently.White-backed planthopper (WBPH, Sogatella furcifera(Horvath)) is the main vector of SRBSDV, once it catches the virus, it will be poisoned for life. Both the nymph and the adult can transmit this virus, but cannot go down through egg. From 2002 to 2008, this virus mainly harmed rice fields in South China. The strong migration trait of WBPH leads to fast spread, difficult prevention and hazard loss on rice. In 2009, the virus harmed more than 300 thousand hectares in 9 provinces of South China and 42 thousand hectares in 19 provinces of North Vietnam, some fields failed. In 2010, it spread more quickly, more than 1.3 million hectares in 13 provinces of South China and more than 60 thousand in 29 provinces of North-central Vietnam had been infected by this virus. From the beginning to the Early March in 2011,50 thousand hectares winter rice in Hainan and 38 provinces of Vietnam had been showed poisoning. This virus would damage more than 2 million hectares rice in south China.Recently, although some reports about SRBSDV itself have existed, but the macroscopic research hasn't been noticed. For this reason, Zhejiang, Jiangxi and Anhui as the representative research object had been chosen for the analysis of the virus source areas spatio-temporal rule of SRBSDV transmission by using the light-trapped data as the research basis, combined with the SRBSDV incidence area data, related atmosphere data, geographic data, GIS,GrADS,MICAPS etc. applied software, and the overlapping tech of the SRBSDV incidence areas and the WBPH emigrants source areas under the ArcGIS software system. This research also found out the kinetics rule of the concentrate landing of WBPH through the systematic analysis of the relationships between the migratory processes and the synoptic meteorology. It will provide technique and basic parameters for the announcement of relationships between WBPH migration and transmission of SRBSDV in China. The major findings were as follows:1. The setting methods of all the main parameters in trajectory simulationThe main biological parameters in trajectory simulation of WBPH are the starting height, the starting moment, the continuous flight time and the interval time for simulation. After the trajectory simulation of 9 heights included in WBPH spring and summer flying heights, 1000m,1500m, and 2000m heights were determined as the starting heights for back-trajectory simulation. Because the WBPH takes off at dusk and dawn, combined with the sunrise and sunset time calculation software,19 o'clock and 5 o'clock are the taking-off time of WBPH. The longest sustained flight time of WBPH is 30h, the landing time in insect gathering area is from 19 o'clock to next 6 o'clock (the lighting time of lure insects light). For this reason, the longest continuous flight time of the dust taking-off type is 30h, and the time of the dawn taking-off type is 25h. Besides, after evaluating the density of the trajectory lines and the coverage area,2h interval is the most suitable time for back-trajectory simulation.2. The virus source distribution range and the main poisoning period of Zhejiang and AnhuiIn 2009, SRBSDV was first found in the late rice in Wuyi, Zhejiang, and the seeding period was the key period for catching this virus. Through the overlapping analysis of the virus incidence area and the possible source regions of WBPH through backward trajectory simulations, the virus source areas of Wuyi were mainly distributed in Guangdong, Guangxi, southern Fujian and southern Jiangxi provinces. The insects from source fields were carrying under the horizontal airflow such as the southwest wind and the southerly wind to Wuyi, and then land intensively under rain or downdraft. Late rice in Wuyi caught this virus, showed dwarf and no heading. During the seeding period of late rice, the peak period of WBPH was from June 28th to 30th in 2009, Wuyi. The virus sources distributed in south Jiangxi, northeast Guangxi and northwest fields in Guangdong. At the end of June, all these rice fields had records of WBPH massive emigration swarm, and the prevailing southwest airflow was useful for the northwards migration of WBPH, later on, the strong rain fall process from the Middle-lower Yangtze area to the eastern part of southwest area was the main pressure for this descending. From June 28th to 30th was the major period of catching SRBSDV in 2009, Wuyi.In 2009, the virus source areas of Huizhou were mainly distributed in Guangdong, Guangxi, Hunan and Jiangxi. From July 20th to 23rd and July 26th to 28th were the main periods for catching virus WBPH landed in Huizhou. Southwest Jiangxi and Eastern Hunan were the main source fields provided SRBSDV. The seeding period was the key period for catching virus WBPH landed and transmitted virus in Huizhou.3. The virus source incidence analysis of SRBSDV in JiangxiTake Jiangxi province as the model of regions South Yangtze rice field, through the comprehensive analysis of the light-traped data in Shangyou, Yongfeng and Nancheng from 2009 to 2010, and the overlapping analysis tech of the virus incidence area and the possible source regions of WBPH getting from backward trajectory simulations, south Jiangxi and north Jiangxi regions were determined as the virus source areas. The results showed that the circumstances of virus source distribution were similar in 2009 and 2010. South Jiangxi could provide catching virus WBPH to middle-north Jiangxi, the main poisoning periods in different rice fields were different.Shangyou located in the south of Jiangxi, the virus source areas distributed in southern Guangdong, southeastern Guangxi and Hainan. The major descending period of WBPH was from middle May to middle June, the early rice there has passed jointing period and the late rice of double planting just started to sowing or raise seedling, both of these periods were not suitable for SRBSDV to infect. But only the single late rice was the seeding stage, which was the most favorable period for the catching virus WBPH to descend and transmit SRBSDV.Yongfeng located in the west of mid north Jiangxi, the virus source fields were southern Jiangxi, Guangdong, Guangxi, Fujiang, Hunan and Hainan. The main immigration period was at middle and late ten days of July, during these times the early rice has reached the period of reaping, and the single rice was booting during this time. Only the double late rice has been transplanted during the late July, which was the most suitable period for catching SRBSDV to transfecting. As a result, the seeding period was the key period for the whole year prevention of SRBSDV.Nancheng located in the east of mid north Jiangxi, the virus source fields were the same as Yongfeng, the main immigration period of it was early June and from late June to early July. In early June, the early rice has reached jointing period, the double planting late rice was just sowing, both of which were not suitable for SRBSDV to infect. But the single late rice was in the period of seeding, or transplanting and tillering, it was easy to catch the virus. However, from late June to early July, the single rice has reached jointing period, the double late rice was still seeding, which were the key periods of catching SRBSDV. For this reason, the seeding period in both seeding bed and rice fields of single rice, and the seeding period of late rice were the key periods for prevention of SRBSDV in Nancheng.