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Systemic induction of salicylic acid-related plant defences in potato in response to Rhizostonia solani AG3PT.

The necrotrophic pathogen Rhizoctonia solani affects potato (Solanum tuberosum) quality worldwide. The pathogen infects below-ground parts of potato during growth. Very little information is available on the extent of colonization of roots by R. solani AG3PT and especially on the defence responses in roots following sprout inoculation with the pathogen. It was hypothesized that infection of the primary sprout results in colonization of the roots by the pathogen, and that R. solani as a necrotroph induces jasmonic acid/ethylene (JA/ET)-related defence responses in sprouts and in the root. Seven well-described genes of general defence responses against fungal pathogens were selected for this study. The expression of these genes was investigated at the transcript level and, for four genes, at the protein level in roots and sprouts at 3, 6 and 13 days post-inoculation (dpi). In addition, the density of colonization of roots with R. solani AG3PT was analysed. Roots were quickly colonized by R. solani following sprout inoculation; however, the rapidly growing root was not further extensively colonized by the pathogen. Furthermore, an increase in transcript and protein levels of the defence-related genes associated with JA/ET- (PR-2) and SA-dependent pathways (PR-1, PR-3 and PR-10) was detected in roots and sprouts at 3 and 6 dpi. However, the susceptible potato cultivar was not able to maintain the elevated transcript level of defence-related genes in roots and sprouts. The results underline that not only the JA/ET- but also the SA-dependent pathway plays a role during interaction of the necrotrophic pathogen R. solani AG3PT with its host potato.

*Genzel, F.; Franken, P.; Witzel, K.; Grosch, R. 2017. Systemic induction of salicylic acid-related plant defences in potato in response to <i>Rhizostonia solani</i> AG3PT. Plant Pathology.

DOI: 10.1111/ppa.12746