Effects Of Southern Rice Black-Streaked Dwarf Virus On Performance Of Its Vector, Sogatella Furcifera (Horvath)

Southern rice black-streaked dwarf virus (SRBSDV) was discovered in2001and since then, occurrence of the virus had spreaded throughout southern China, Vietnam and even Japan. SRBSDV is a new species in genus Fijivirus, family Reoviridae, vectored by white-backed planthopper (WBPH), Sogatella furcifera. To elucidate the interaction among rice, WBPH, and SRBSDV, this study investigated influence of SRBSDV on the performance of WBPH, including growth, development, reproduction, feeding behavior, and nutritional composition.1. Influence of SRBSDV on the performance of WBPH.To elucidate the influence of SRBSDV on performance of WBPH, life parameters of viruliferous and non-viruliferous WBPH feeding on infected or uninfected rice seedlings were measured in a factorial design. It was found that, regardless of infection status of rice seedlings, viruliferous WBPH nymphs took longer time to develop from nymph to adult than the non-viruliferous nymphs. Viruliferous WBPH females deposited fewer eggs than non-viruliferous females, while on infected rice seedlings, both viruliferous and non-viruliferous WBPH females laid fewer eggs than on uninfected seedlings. Longevity of WBPH females was affected by a significant interaction between infection status of rice plant and WBPH. Non-viruliferous WBPH females feeding on infected rice seedlings lived longer than viruliferous and non-viruliferous females on uninfected rice seedlings. However, the sex ratio, adult weight and wing form ratio of WBPH were irrelevant with the infection status of both rice seedling and WBPH. These results indicate that performance of WBPH is partially affected by SRBSDV either directly (by infection of WBPH) or indirectly (by infection of rice plant).2. Influence of SRBSDV on the feeding behavior of WBPH.The detailed feeding behaviors of WBPH were monitored by EPG (electrical penetration graph) during SRBSDV transmission (from viruliferous WBPH to uninfected rice plant) and acquisition (from infected rice plant to non-viruliferous WBPH), with non-viruliferous WBPH feeding on uninfected rice plant as the control. During virus transmission, total probing frequency, total duration and frequency of N2waveform, frequency of N4-a and N4-b waveform were higher in virus-transmitted WBPH than in virus-not-transmitted ones, while total duration of N4-a and N4-b waveform were not different among the treatments. During virus acquisition, average duration per probing was longer in virus-acquired WBPH than in the control WBPH. Initial np (non-penetration) duration of virus-acquired WBPH was significantly shorter than virus-not-acquired WBPH. Total duration and frequency of N2, N3, and N4-a were significantly reduced in virus-acquired WBPH as compared with the control, while total duration and per probing duration of N4-b were longer in virus-acquired WBPH than in the control and virus-not-acquired WBPH. 3. Influence of SRBSDV on concentrations of free amino acid and sugar in WBPH honeydew and rice ploem sap.Honeydew was collected from viruliferous and non-viruliferous WBPH fed on infected or uninfected rice seedlings, phloem sap was from infected and uninfected rice seedlings with or without WBPH feeding. Amino acid concentration in phloem sap of infected rice seedling was higher than that of uninfected rice seedling. When the rice plants were exposed to feeding by WBPH, phloem sap amino acid concentration decreased in uninfected rice seedlings but increased in infected rice seedlings. Without WBPH feeding, phloem sap sugar concentration was lower in the infected than in the uninfected rice seedlings, but increased significantly in both infected and uninfected rice plants after being fed by WBPH. In honeydew of non-viruliferous WBPH, amino acid concentration was about1fold higher when the insects were fed on uninfected rice seedlings than on infected seedlings. For honeydew of viruliferous WBPH, amino acid concentration was higher when the insects were on infected seedlings than on uninfected seedlings. Amino acid concentration of non-viruliferous WBPH fed on infected rice seedlings was the lowest. Regardless of infection status of rice seedlings, honeydew sugar concentration was higher in viruliferous WBPH than in non-viruliferous WBPH. Regardless of infection status of WBPH, daily honeydew excretion was more on infected seedlings than on uninfected seedlings. On uninfected rice seedlings, viruliferous WBPH excreted more honeydew than non-viruliferous WBPH.