Identification the pathogen of alfalfa virus disease in some areas of Tibet

Medicago sativa viral diseases were surveyed in partial planting areas of Zhanang County, Dazi County and Nyingchi City in Tibet Autonomous Province. The results showed that viral diseases occurred in all the above regions with symptoms of mosaic, smaller leaves, mottle, shrinking, reddening and yellowing. To identify the disease plants’ potential pathogen, deep sequencing and RT-PCR technology were conducted on 211 symptomatic leaves samples collected in August 2020 and July 2021. Four viruses of alfalfa mosaic virus (AMV), M. sativa virus 1 (MsAV1), lucerne transient streak virus (LTSV) and cucumber mosaic virus (CMV) were found infecting these samples with a total detection rate of 31.8%. The detection rates of AMV, MsAV1, LTSV and CMV were 17.1%, 10.4%, 3.3% and 5.7% respectively. The complex infection occurred between two viruses with the detection rate of AMV + MsAV1 1.4%, AMV + LSTV 2.4%, CMV + MsAV1 and AMV + CMV 0.5%. This is the first report of AMV, MsAV1and LTSV in Tibet and CMV in alfalfa in China. These results will provide a reference for preventing and controlling alfalfa virus disease in Tibet.