Abstract
BackgroundLate blight seriously threatens potato cultivation worldwide. The severe and widespread damage caused by the fungal pathogen can lead to drastic decreases in potato yield. Although grafting technology has been widely used to improve crop resistance, the effects of grafting on potato late blight resistance as well as the associated molecular mechanisms remain unclear. Therefore, we performed RNA transcriptome sequencing analysis and the late blight resistance testing of the scion when the potato late blight-resistant variety Qingshu 9 and the susceptible variety Favorita were used as the rootstock and scion, respectively, and vice versa. The objective of this study was to evaluate the influence of the rootstock on scion disease resistance and to clarify the related molecular mechanisms.ResultsA Kyoto Encyclopedia of Genes and Genomes pathway enrichment analysis revealed that the expression levels of genes related to plant–pathogen interactions, plant mitogen-activated protein kinase (MAPK) signaling pathways, and plant hormone signal transduction pathways were significantly up-regulated in the scion when Qingshu 9 was used as the rootstock. Some of these genes encoded calcium-dependent protein kinases (CDPKs), chitin elicitor receptor kinases (CERKs), LRR receptor serine/threonine protein kinases (LRR-LRKs), NPR family proteins in the salicylic acid synthesis pathway, and MAPKs which were potato late blight response proteins. When Favorita was used as the rootstock, only a few genes of late blight response genes were upregulated in the scion of Qingshu 9. Grafted plants using resistant variety as rootstocks inoculated with P. infestans spores showed significant reductions in lesion size while no significant difference in lesion size was observed when susceptible variety was used as the rootstock. We also showed that this induction of disease resistance in scions, especially scions derived from susceptible potato varieties was mediated by the up-regulation of expression of genes involved in plant disease resistance in scions.ConclusionsOur results showed that potato grafting using late blight resistant varieties as rootstocks could render or enhance resistance to late blight in scions derived from susceptible varieties via up-regulating the expression of disease resistant genes in scions. The results provide the basis for exploring the molecular mechanism underlying the effects of rootstocks on scion disease resistance.
Highlights
Late blight seriously threatens potato cultivation worldwide
Resistance of potato to late blight after grafting At 35 days after grafting, the F/F, F/Q, Q/Q, and Q/F scion leaves were collected for an in vitro inoculation assay, with leaves from ungrafted F and Q plants serving as controls
When using the highly resistant variety Q as rootstocks, the proportion of diseased spots in susceptible variety was reduced by 51.03% and 39.31% respectively compared with the ungrafting and selfgrafting, which were significant (P < 0.05)
Summary
Late blight seriously threatens potato cultivation worldwide. Late blight has drastically decreased potato yields, including losses of up to 100% in some cases. Annual direct economic losses due to late blight infections worldwide are as high as US $6.7 billion, which corresponds to 15% of the total potato output [3]. Favorita, which is a highyielding potato variety that produces high-quality tubers, was introduced to China from the Netherlands in 1981 by the China-owned Assets Supervision and Administration Bureau of the Central Ministry of Agriculture. Favorita is a high-yielding potato variety that produces high-quality tubers and was introduced to China from the Netherlands. An outbreak of late blight will seriously impact the yield and quality of Favorita potatoes [4]. There is a critical need for enhancing the late blight resistance of Favorita
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