Quantitative analysis of Rice stripe virus in a transovarial transmission cycle during the development and reproduction of its vector, Laodelphax striatellus.

The amount of Rice stripe virus (RSV) maintained through transovarial transmission was analyzed during the development and reproduction of its vector, Laodelphax striatellus. Reverse transcription quantitative PCR analysis was used to quantify RNA expressed from the RSV coat protein (CP) gene as an estimate of RSV content in nymphs and adults of L. striatellus at various developmental stages. The 18S ribosome RNA gene of L. striatellus was chosen as the reference for calculating RSV CP expression using the comparative Ct method. Based on the CP transcript levels, the amount of RSV did not differ significantly throughout the nymphal stage or between adult females of different ages; however, RSV content tended to increase slightly as males became older. The average RSV content in males was 1.30-2.49 times that in females. The amount of RSV in L. striatellus adults was compared between generations. The RSV content of female adults did not differ significantly between the parent and progeny populations three of three different females. L. striatellus grown to adults on a susceptible cultivar and five RSV-resistant cultivars were compared to analyze whether the amount of RSV varied among cultivars. Although the amount of RSV in L. striatellus adults differed significantly among the six rice cultivars evaluated, the difference seemed independent of whether resistance genes were present. In addition, the percentage of viruliferous insects was similar among cultivars.