Transcriptome Analysis of Grafted Potato Rootstock for Improvement of Scion Late-Blight Resistance

Late blight seriously threatens potato cultivation worldwide. Damage caused by the fungus, which is severe and widespread, can lead to drastic reductions in potato yield and even total loss. Although grafting technology has been widely used to improve crop resistance, the effects and associated molecular mechanisms of grafting on resistance to potato late blight are unclear. In this study, we therefore performed RNA transcriptome sequencing of the scion when potato late blight-resistant variety Qingshu 9 and susceptible variety Favorita were used as the rootstock and scion, respectively, and vice versa. Using the sequencing results, we analyzed the influence of the rootstock on scion resistance and related molecular mechanisms. Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis revealed that plant–pathogen interactions, the plant MAPK signaling pathway, and genes on the SA pathway were significantly up-regulated in the scion when Qingshu 9 was used as the rootstock. When Favorita was used as the rootstock, β-ketoacyl-CoA synthase-related genes in the scion, Qingshu 9, were significantly down-regulated. Resistance to late blight on scion leaves were also tested in vitro, which results consistent with those obtained by sequencing. All the generated evidence indicates that the use of resistant and susceptible varieties as rootstocks can respectively increase and reduce resistance to late blight. Our sequencing results further elucidate the molecular mechanism underlying the post-grafting effects of rootstocks on late blight resistance and provide a theoretical basis for the transfer of resistance genes between scions and rootstocks after grafting.