| Abstract: Rice planthoppers, including Brown planthopper （BPH）, Nilaparvatalugens （Stal）, and White-backed planthopper （WBPH）, Sogatella furcifera （Horvath）,is one of the most important rice pests in China. The outbreak reasons of BPH andWBPH include earlier immigration time, more immigration events and numbers, andhigher reproductive rate. It caused a great threat to the rice production in China, andhas become one of the main factors that affected rice yield and quality. The riceplanthoppers are transported by wind during take-off and landing progress. Thus,atmospheric circulation and weather conditions directly determine the landing areaand time, and further determine the original population of these pests. Our studyfocused on how weather conditions influenced WBPH take-off behavior throughfield observation. Then we analyzed the potential source areas of WBPH and BPHimmigrated in Jiangxi province in May and June in2007, and weather conditionsthat driven the migration of WBPH and BPH in the air. By using the technology ofmolecular biology, we successfully cloned BPH heat shock protein gene hsp70cDNA fragment and laid the foundation for further study of the hsp70expressionand regulation of BPH, and also provided a new way to explain the physiologicalmechanism of autumn warm temperature on BPH later outbreak. Finally, we built asimulation model for climatic factors that influenced the occurrence area of WBPHand BPH. Our results provided useful information for the early warning of BPH andWBPH problems and gave suggestions for the establishment of integrated pestmanagement strategies in the rice production in related areas.Part I. Weather factors to influence the taking-off behavior of white-backedplanthopper （WBPH）The take-off behavior influenced by weather factors, such as light intensity,temperature, relative humidity and pressure etc., were well studied by manyscientists. Most studies suggested that WBPH take-off during down and dusk, andnone or very few through the night. However, how rainfall influenced the take-offbehavior of WBPH through night was unclear. We monitored the WBPH take-off behavior using Malaise trap during night at half-an hour basis till the capture numberof adult WBPH was close to zero. Then we analyzed the relationship betweenmeteorological factors such as precipitation, horizontal wind speed, wind direction,vertical wind speed, temperature, humidity, and BPH take-off number at night.Results showed WBPH took-off during night when it was raining, and ceasedwhen rain stopped. The adult taking-off number at night showed a highly significantpositive correlation(R=0.794**)with precipitation. The half-hourly taking-off numberwas significantly correlated (R=0.376**) with precipitation. It suggested that rainfallsomehow triggered the taking-off of WBPH during night. During day-time, WBPHhardly took-off when there was no precipitation. The half-hourly taking-off numberalso significantly correlated with air temperature ((R=-0.321**), air humidity(R=0.278**), and horizontal wind speed （R=-0.206*）. However, none significantcorrelation was found among standard deviation of vertical wind speed and winddirection. Results also showed that the taking-off behavior of WBPH has an obviousdaily rhythm-two take-off peaks appeared at dusk and dawn.Part II. The insect-source site and the weather condition of the progress of riceplanthopper moved to Jiangxi province in2007We analyzed the light catch data from multiple sites in Jiangxi province in2007.Move the trajectory simulation of the peak day in order to find the insect source.Combined with the analysis of meteorological conditions in migration period, weexpounded the early immigration insect source and promote its centralized landingmeteorological factors.Results showed that the early immigration insect source of Jiangxi province in2007is focus on Western Guangdong province、Eastern Guangxi province andHainan province. The main weather process that effect the migration was cold fronts,stationary front, the low-lever jet at the west and north side of subtropical highgenerated by the airflow convergence zone. Cause of insect landing was mainlybecause of precipitation, low-level jet, convergence zone, and the vertical motion ofthe flow. The results provided academic basis for different prediction andfountainhead management of rice planthopper. Part III. The cloning of brown planthopper heat shock protein gene hsp70cDNA clipsHeat shock protein HSP70plays an important role in the thermal adaptation ofinsects. We successfully cloned the heat shock protein gene70（hsp70） cDNAfragments of Brown Planthopper. We got two cloned fragments, by comparison withpart of the HSP70protein family. We found that both of them have the signaturesequence （IFDLGGGTFDVSIL, VLVGGSTRIP）. Thus, we supposed that both ofthem are the gene fragments encoding the HSP70protein. Comparing with theHSP70from other insects, we preliminary identified that X2encoded HSP70, whileX1encoded HSC70. Results provided a new way to explain the physiologicalmechanism of temperature on BPH outbreak in autumn. It also suggested that furtherstudy of the hsp70expression regulation of brown planthopper were needed to betterunderstanding the adaptive mechanisms to the heat conditions.Part IV. Prediction of rice planthopper occurrence areas based on theatmospheric circulation characteristicsSuitable atmospheric circulation is the power and carrier of rice planthopper andother insects during the migratory progress. We analyzed the historic data ofatmospheric circulation characteristics and the planthopper occurrence areas inChina. We selected the statistically significant related factors to establish the bestfitting models by using stepwise regression. The significant related factors, such asSubtropical high intensity index, Subtropical area index, North boundary ofsubtropical high, Polar vortex index, Polar vortex area index and etc., were used toestablish the forecasting model to predict rice planthopper occurrence area. Thisforecasting model will gave us a hint to predict the damage situations caused by riceplanthopper and give the potential early warning suggestions to the earlymanagement of rice pests in the rice production areas. |
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