Effects of Two Citrus Tristeza Virus Isolates on Sweet Orange (Citrus sinensis) Propagated on a Citrus Tristeza Virus Tolerant Rootstock: A Metabolomics and Transcriptomics Approach

Citrus tristeza virus (CTV) was once the most economically important citrus pathogen in the world. In regions where CTV is endemic, CTV tolerant rootstocks have been widely adopted. Despite these changes, CTV can still affect plant health and fruit quality. To assess the impact of CTV infection on scions grown on CTV tolerant rootstock, Washington navel [Citrus sinensis (L.) Osbeck] scions grafted onto Carrizo rootstock (Poncirus trifoliate × Citrus sinensis) received grafts from citrus infected with a mild isolate (T30 isolate 07539) or a stem-pitting isolate (CCTEA-107) of CTV, and metabolomics and transcriptomics analyses were performed over a period of 10 months after grafting of CTV-infected material. The phenotypic response to either isolate was weak. The largest difference in the leaf metabolome was seen 10 months postgrafting for both isolates, with a stronger response observed for plants infected with the stem-pitting isolate. Analysis of differentially expressed genes revealed that plants infected with the milder isolate exhibited a difference in gene expression 4 months after infection, whereas plants infected with the stem-pitting isolate exhibited a difference in gene expression 10 months after infection. This study highlights differences and similarities in the metabolome and transcriptome response of Washington navel trees on Carrizo rootstock to two CTV isolates.