Physiological response of Poncirus trifoliata rootstock to infection by an RB of Citrus tristeza virus isolate

Abstract

In citrus growing areas where Citrus tristeza virus (CTV) is endemic, Poncirus trifoliata is commonly used as a rootstock to prevent tree decline. However, resistance breaking (RB) CTV isolates, capable of systemically infecting P. trifoliata, have been identified. Never-theless, their effects on the rootstock remain understudied. Therefore, the aim of this work was to evaluate the physiological response of P. trifoliata to infection by a local RB isolate (RB-UY1), and determine its effects on grafted scions, using Navel orange (N/P. trifoliata) and Mexican lime (ML/P. trifoliata) as models. Growth parameters, symptoms expression, photosynthetic activity, and oxidative stress were periodically recorded. The results showed that the photosynthetic activity was not affected by the RB-UY1 isolate in P. trifo-liata nor in grafted scions. Oxidative damage was not detected in any treatment, despite higher levels of hydrogen peroxide and superoxide radicals in RB-inoculated plants. Nonetheless, a decline in growth was recorded in P. trifoliata and ML/P. trifoliata, but not in N/P. trifoliata. In response to the RB-UY1 infection, there was a significant increase in total phenol concentration in the rootstock and N/P. trifoliata; however, enzyme activity of catalase and ascorbate peroxidase did not differ among treatments. In conclusion, infection by the RB-UY1 isolate affected growth rootstock over time, but did not compromise the physiological performance of N/P. trifoliate scion. These findings demonstrate a clear host-viral isolate interaction and underscore the need for further studies to elucidate the underlying mechanisms of host response to RB-CTV isolates.