Incidence and distribution of insect-transmitted cereal viruses in wheat in China from 2007 to 2019

Diseases caused by insect-transmitted viruses are the predominant constraint to wheat production worldwide. However, detailed knowledge of virus incidence and dynamics in China in recent years is very limited. Here, major wheat-growing regions of China were surveyed over 10 years for insect-transmitted viruses, and 2,143 samples were collected (in 2007 to 2015) and analyzed by molecular hybridization or multiplex reverse-transcription PCR for barley yellow dwarf viruses (BYDVs: BYDV-GAV, -GPV, and -PAV) and wheat dwarf virus (WDV). In a 4-year survey (2016 to 2019), the incidence of eight insect-transmitted viruses (BYDVs, WDV, wheat yellow striate virus [WYSV], barley yellow striate mosaic virus [BYSMV], northern cereal mosaic virus [NCMV], and rice black-streaked dwarf virus [RBSDV]) was investigated, and BYDVs and WDV were widely distributed across China. BYDV-GAV (29.0% of the tested sample) was the most abundant, followed by BYDV-PAV (23.2%) from 2007 to 2015. From 2016 to 2019, however, BYDV-PAV had become the predominant species (39.5% positive of 952 samples tested), while the incidence of BYDV-GAV (13.4%) had declined. During the entire survey, the incidence of BYDV-GPV was very low in some locations in northwestern and northern China, and all eight viruses caused only local epidemics, not large-scale outbreaks throughout China. Two new cereal-infecting rhabdoviruses, leafhopper-transmitted WYSV and planthopper-transmitted BYSMV, were also found in China in recent years.