Grafting to manage infections of top stunting and necrogenic strains of cucumber mosaic virus in tomato

Abstract

Cucumber mosaic virus (CMV) lists among the most important etiological agents of tomato diseases. Some isolates of CMV function as helper virus for replication, encapsidation and transmission of satellite RNAs (satRNA), which may exacerbate symptoms induced by CMV in certain hosts. Outbreaks of CMV strains supporting hypervirulent variants of satRNAs are recurrent in tomato with devastating effects on crop production and efficient control measures are still unavailable. In this study, we examined the dynamics of infection of the CMV strains tomato top stunting (TTS) and 77 supporting replication of satRNA variants that codetermine top stunting (TTS‐satRNA) and necrotic (77‐satRNA) phenotypes in two tomato cultivars denoted Solanum lycopersicum Manduria (Sl‐Ma) and S. lycopersicum UC82 (Sl‐UC). Sl‐Ma but not Sl‐UC recovered from disease symptoms induced by CMV‐TTS while both the cultivars succumbed to the infection of CMV‐77 and its necrogenic satRNA. Ability to recover of the Sl‐Ma plants was transmitted by grafting to the susceptible genotype Sl‐UC. More interestingly, recovery was observed also against the challenge inoculation of CMV plus 77‐satRNA in plants grafted on Sl‐Ma and in self‐grafted plants of both the Sl‐Ma and Sl‐UC cultivars. Analysis of small RNAs and genes of the defence plant response based on RNA interference (RNAi) suggested that RNAi is involved in the recovery of Sl‐Ma against CMV with hypervirulent satRNAs and in scions grafted on this rootstock. The response of Sl‐Ma to the inoculation of CMV‐77 plus 77‐satRNA was compared with that of the transgenic tomato line S. lycopersicum transgenic line UCTC5.9.2 that expresses constitutively the benign variant of the satRNA denoted Tfn‐satRNA. Comparative analysis suggested that the response may operate via similar mechanisms, which involve RNAi, the graft and the presence of the satRNA.

BiodiverSO: A Case Study of Integrated Project to Preserve the Biodiversity of Vegetable Crops in Puglia (Southern Italy)

“…Spanò et al [25] For example, Pavan et al [12] used genotyping-by-sequencing (GBS) to characterize patterns of genetic diversity and genomic features within Cucumis melo L. Analyses of genetic structure, principal components, and hierarchical clustering supported the identification of three distinct subpopulations. One of them includes accessions of the local variety Carosello, referable to the chate taxonomic group.…”

“…A Wikipedia page about the PC was created from scratch (http://wiki.biodiversitapuglia.it/Carota_di_Polignano), receiving more than 15,000 page views in less than two years [25]. Moreover, a descriptive sheet was also realized and shared for users (https://biodiversitapuglia.it/varieta-orticole/carota-di-polignano/).…”

Grafting alters tomato transcriptome and enhances tolerance to an airborne virus infection

“…However, most of the economic losses are now compensated by the reduced number of plants required per cultivation area unit, noticeable increases in fruit yield, reduced use of chemical fertilizers, improved economic use of irrigation water, earliness of the produce and extension of the growing season. These traits rely mostly on the rootstock genotype and on the large and vigorous root systems of grafted plants that ensure the maintenance of good plant vigor and suitable levels of disease resistance or tolerance until late in the growing season [1][2][3][4][5][6] .…”

“…Ma is a rustic plant with a robust root apparatus, good resistance to drought and thick fruit skin, which ensure long shelf-life. These characteristics made Ma a promising rootstock to confer suitable levels of tolerance against two arthropod-transmitted viruses 5,6 listed among the top ten economically important plant viruses for which there are no efficient and environmentally friendly methods of control 7 .…”

“…Yet, the mechanisms through which such graft-induced systemic tolerance works have not been elucidated 8,13 . Some of us have shown that grafting on the Ma rootstock may induce tolerance in tomato against infections of a Sw-5 resistance breaking strain of TSWV 5 and of severe cucumber mosaic virus (CMV) strains supporting hypervirulent satellite RNAs (satRNAs) that co-determine stunting and necrotic phenotypes in tomato 6 . The evidences provided in both the studies suggest that the Ma rootstock may induce systemic tolerance to viral infection via the adaptive defense response based on RNA interference (RNAi), which is a sequence identity-dependent RNA degradation mechanism conserved in plants, invertebrates, fungi and oomycetes [14][15][16][17] .…”