Rootstock‐induced scion resistance against tobacco mosaic virus is associated with the induction of defence‐related transcripts and graft‐transmissible mRNAs

Abstract

AbstractGrafting is a common horticultural practice used to confer desirable traits between rootstock and scion, including disease resistance. To investigate graft‐conferred resistance against viral diseases a novel heterografting system was developed usingNicotiana benthamianascions grafted onto different tomato rootstocks.N. benthamianais normally highly susceptible to tobacco mosaic virus (TMV) infection. However, specific tomato rootstock varieties were found to confer a range of resistance levels toN. benthamianascions inoculated with TMV. Conferred resistance was associated with delays in virus accumulation and the reduction in virus spread. RNA sequencing analysis showed the enrichment of transcripts associated with disease resistance and plant stress inN. benthamianascions grafted onto resistance‐inducing tomato rootstocks. Genome sequencing of resistance‐ and nonresistance‐conferring rootstocks was used to identify mobile tomato transcripts withinN. benthamianascions. Within resistance‐inducedN. benthamianascions, enriched mobile tomato transcripts were predominantly associated with defence, stress, and abscisic acid signalling when compared to similar scions grafted onto nonresistance‐inducing rootstock. Combining these findings suggests that graft‐induced resistance is modulated by rootstock scion transcriptional responses and rootstock‐specific mobile transcripts.