Quantitative Distribution and Transmission of Tea Plant Necrotic Ring Blotch Virus in Camellia sinensis

Abstract

Tea plant necrotic ring blotch virus (TPNRBV), which carries four positive-sense single-stranded RNA segments, causes discoloration spots and multiple necrotic ring blotches in tea trees. To understand the distribution and transmission of TPNRBV in tea trees and prevent its spread, a SYBR Green real-time quantitative polymerase chain reaction (RT-qPCR) method for detecting the four virus segments was developed. The limit of detection of RT-qPCR was 3.81, 4.73, 3.58, and 4.64 copies/μL for the four strands of TPNRBV, which was 100-fold more sensitive than conventional PCR for RNA1 detection, 10-fold for RNA2 and RNA3, and 1000-fold for RNA4 detection. Visual observation and RT-qPCR of different tea plant tissues showed that symptomatic mature leaves contained the highest TPNRBV load; the concentrations of the four RNAs in other tissues decreased or were undetectable with increasing distances from symptomatic leaves. TPNRBV did not spread efficiently through seeds, cuttings, or mechanical inoculation, but was transmitted to some tea cultivars, particularly light albinistic varieties such as ‘Zhonghuang 1’ and ‘Huangjinya’, under field conditions. Our TPNRBV detection method is useful for determining the distribution and transmission characteristics of TPNRBV and selecting tissues with the highest viral load for early diagnosis, monitoring, and management of the disease.