Viruliferous rate of small brown planthopper is a good indicator of rice stripe disease epidemics.

Rice stripe virus (RSV), its vector insect (small brown planthopper, SBPH) and climatic conditions in Jiangsu, China were monitored between 2002 and 2012 to determine key biotic and abiotic factors driving epidemics of the disease. Average disease severity, disease incidence and viruliferous rate of SBPH peaked in 2004 and then gradually decreased. Disease severity of RSV was positively correlated with viruliferous rate of the vector but not with the population density of the insect, suggesting that the proportion of vectors infected by the virus rather than the absolute number of vectors plays an important role in RSV epidemics and could be used for disease forecasting. The finding of a positive correlation of disease severity and viruliferous rate among years suggests that local infection is likely the main source of primary inoculum of RSV. Of the two main climatic factors, temperature plays a more important role than rainfall in RSV epidemics.

One-step reverse transcription loop-mediated isothermal amplification for the rapid detection of cucumber green mottle mosaic virus.

Cucumber green mottle mosaic virus (CGMMV) has caused serious damage to Cucurbitaceae crops worldwide. The virus is considered one of the most serious Cucurbitaceae quarantine causes in many countries. In this study, a highly efficient and practical one-step reverse transcription loop-mediated isothermal amplification (RT-LAMP) was developed for the detection of CGMMV. The total RNA or crude RNA extracted from watermelon plants or seeds could be detected easily by this RT-LAMP assay. The RT-LAMP assay was conducted in isothermal (63°C) conditions within 1h. The amplified products of CGMMV could be detected as ladder-like bands using agarose gel electrophoresis or visualized in-tube under UV light with the addition of a fluorescent dye. The RT-LAMP amplification was specific to CGMMV, as no cross-reaction was observed with other viruses. The RT-LAMP assay was 100-fold more sensitive than that of reverse-transcription polymerase chain reaction (RT-PCR). This is the first report of the application of the RT-LAMP assay to detect CGMMV. The sensitive, specific and rapid RT-LAMP assay developed in this study can be applied widely in laboratories, the field and quarantine surveillance of CGMMV.

[QTL analysis for rice stripe disease resistance gene using recombinant inbred lines (RILs) derived from crossing of Kinmaze and DV85].

Rice stripe disease transmitted by small brown planthopper (Laodelphax striatellus Fall.) is one of the most serious viral diseases in East Asia. The disease is severely epidemic in most rice growing areas where the main cultivars are susceptible or moderately susceptible to rice stripe virus. In this research, a recombinant inbred lines (RILs) population of 81 lines derived from a cross of Kinmaze (japonica)/DV85(indica) by the single seed descent method was used to detect quantitative trait loci (QTL) conferring resistance to rice stripe virus(RSV). The response of the two parents and 81 RILs to RSV were investigated by inoculating seedlings with viruliferous small brown planthopper insects, and scored by the disease rate index. The quantitative trait loci for rice stripe disease resistance were analyzed by QTL Cartographer software. Three QTL controlling RSV resistance were detected on chromosomes 1, 7 and 11, respectively. Individual QTL accounted for 19.8%-30.9% of the phenotypic variance in the RILs population. The direction of the additive gene effects at two loci qStv7 and qStv11 coincided with that predicted by phenotypes of the parents. At these two loci, the DV85 alleles increased the resistance to RSV, while at qStv1, the Kinmaze alleles increased the resistance to RSV.