Non-Feeding Transmission Modes of the Tomato Yellow Leaf Curl Virus by the Whitefly Bemisia tabaci Do Not Contribute to Reoccurring Leaf Curl Outbreaks in Tomato.

Simple Summary: Tomato yellow leaf curl virus (TYLCV) poses a serious constraint to tomato production in the Southeastern United States. Since its introduction, it has become endemic in states such as Georgia and Florida despite tomato-free periods. This study examined whether the endemic status of TYLCV is aided by the Bemisia tabaci B cryptic species' vertical and/or horizontal non-feeding modes of TYLCV (the Georgia variant of the Israel strain) transmission. The potential for 'non-feeding' transmission modes has been examined previously, with inconsistent results. The objective of this study was to determine the frequency of TYLCV transovarial and/or sexual (mating) transmission and the subsequent transmissibility of the virus to virus-free plants. The study utilized a series of virus transmission assays and detection and quantitation tools. Our results indicate that non-feeding transmission modes are a rare phenomenon in this pathosystem, and their significance is irrelevant for the observed endemic status of TYLCV in the southeastern United States. Tomato yellow leaf curl virus (TYLCV) causes significant yield loss in tomato production in the southeastern United States and elsewhere. TYLCV is transmitted by the whitefly Bemisia tabaci cryptic species in a persistent, circulative, and non-propagative manner. Unexpectedly, transovarial and sexual transmission of TYLCV has been reported for one strain from Israel. In this study, the potential contribution of the B. tabaci B cryptic species transovarial and sexual transmission of TYLCV (Israel strain, Georgia variant, Georgia, USA) to reoccurring outbreaks was investigated by conducting whitefly-TYLCV transmission assays and virus DNA detection using end point PCR, DNA quantitation via real-time PCR, and virion detection by immunocapture PCR. TYLCV DNA was detectable in four, two, and two percent of first-generation fourth-instar nymphs, first-generation adults, and second-generation adults, respectively, following transovarial acquisition. Post-mating between viruliferous counterparts, the virus's DNA was detected in four percent of males and undetectable in females. The accumulation of TYLCV DNA in whiteflies from the transovarial and/or sexual experiments was substantially lower (100 to 1000-fold) compared with whitefly adults allowed a 48-hr acquisition-access period on plants infected with TYLCV. Despite the detection of TYLCV DNA in whiteflies from the transovarial and/or mating experiments, the virions were undetectable by immunocapture PCR—a technique specifically designed to detect virions. Furthermore, tomato test plants exposed to whitefly adults that presumably acquired TYLCV transovarially or through mating remained free of detectable TYLCV DNA. Collectively, the extremely low levels of TYLCV DNA and complete absence of virions detected in whiteflies and the inability of the B. tabaci cryptic species B to transmit TYLCV to test tomato plants following transovarial and mating acquisition indicate that neither transovarial nor sexual transmission of TYLCV are probable or epidemiologically relevant for TYLCV persistence in this pathosystem. [ABSTRACT FROM AUTHOR]