| ABSTRACT:The small brown planthopper Laodelphax striatellus(Fallen)is a major pest of rice plant in China.It can not only suck rice sap directly,which causes severe damage to rice production,but also transmit rice stripe virus(RSV)and rice black-streaked dwarf virus(RBSDV).The damage of virus transmission is more serious than direct sucking.The electrical penetration graph(EPG)waves in relation to feeding behavior of L.striatellus were identified,and mechanism of RSV transmission was evaluated prelimitarily by using EPG technique.The results are as follows.1.Indentification of EPG waveforms of feeding behavior in L.striatellusThe relationship between EPG waveforms and feeding behavior of L.striatellus was evaluated using electrical penetration graph(EPG)technique.The EPG waveforms and its biological meaning were obtained.The EPG signals of L.striatellus were classified into seven different waveforms,NP,N1,N2-a,N2-b,N3,N4,and N5.They were almost similar to those in Nilaparvata lugens according to their shapes and frequencies.A new special waveform was first identified in the salivation phase of N2.It can be divided into two parts,including N2-a and N2-b.N2-a means salivation and stylet movement,and N2-b means sustained salivation.2.The comparasion of EPG variables among different instars and sex of L.striatellusThe EPG variables among different instars and sex L.stiatellus were compared.The results showed that EPG waveforms of L.striatellus were similar among different instars and sex.However,their feeding processes were different.Females showed higher probe frequency than that of males and young nymphs.The periods of extracellular movement of adults' stylets near the phloem region were longer than that of nymphs.3.The relationship between L.striatellus feeding phases and rice stripe virus transmissionThe EPG combined with real time interruption technique was used to study the relationship of L.striatellus feeding and virus transmission.The results indicated that virus could be acquired during salivation(N2),extracellular movement of stylet near the phloem region(N3)and phloem sap ingestion(N4).However,it could not acquire during stylet penetration(N1).There were no significant differences in virus acquisition rate of L.striatellus when feeding was interrupted at N2 and N3 phases,or at N3 and N4 phases.However,virus acquisition rate of L.striatellus whose feeding were interrupted at N4 phase was 42.86%,and was significantly higher than that of N2 phase(13.89%).Virus transmission mainly happened at salivation phase(N2),extracellular movement of stylet near the phloem region phase(N3),phloem sap ingestion phase(N4).Virus transmission rate of L.striatellus was not significantly different when feeding process was interrupted at different feeding phases.4.Feeding behavior and virus transmission efficiency of L.striatellus on rice varieties with different resistanceThe EPG technique was used to investigate the influence of variety resistance on feeding behavior and virus transmission efficiency.The results showed that there were no significant differences in durations of different feeding behavior(including:non-penetration phase(NP),penetration phase(N1),salivation phase(N2),extracellular movement of stylet near the phloem region phase(N3),phloem sap ingestion phase(N4)),ingestion in xylem phase(N5)),when uninfected L.striatellus were feeding on Wuyujing 3(susceptible varieties)and Yandao 8(resistant varieties).But the virus acquisition rate of L.striatellus feeding on Wuyujing 3 for 12 hours was 40%,which was significantly higher than that of Yandao 8(10%).The duration of N1,N2,N3,N5 phase of virus-infected L.striatellus feeding on Wuyujing 3(susceptible varieties)did not differ significantly from those on Yandao 8(resistant varieties.The duration of NP of infected L.striatellus feeding on Wuyujing 3 was(321.34±29.91)min,and was significantly shorter than that of Yandao 8(429.46±24.96)min.However,the duration of sustained ingestion(N4)on Wuyujing 3(241.44±35.54 min)was significantly longer than that on Yandao 8(108.25± 19.85)min.The virus transmission rate of L.striatellus feeding on Wuyvjing 3 for 12h was 100%,and was significantly higher than that on Yandao 8(63.33%).These results indicated that the rice disease-resistance could affect the virus acquisition and transmission efficiency of L.striatellus.Therefore,cultivation and planting resistant rice variety may be an important strategy for the control rice stripe virus transmission. |
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