Graft-transmissible resistance of cherry pepper (Capsicum annuum var. cerasiforme) to powdery mildew (Leveillula taurica) is associated with elevated superoxide accumulation, NADPH oxidase activity and pathogenesis-related gene expression

Albert, Réka and Künstler, András and Lantos, Ferenc and Ádám, Attila and Király, Lóránt (2017) Graft-transmissible resistance of cherry pepper (Capsicum annuum var. cerasiforme) to powdery mildew (Leveillula taurica) is associated with elevated superoxide accumulation, NADPH oxidase activity and pathogenesis-related gene expression. ACTA PHYSIOLOGIAE PLANTARUM, 39. p. 53. ISSN 0137-5881

Text Graft_transmissible_PM_ResPepper_AlbertActaPhysiolPlant17_u.pdf Restricted to Repository staff only Download (6MB) | Request a copy

Abstract

We found that resistance to pepper powdery mildew (PM) ( Leveillula taurica ) develops in a sweet pepper ( Capsicum annuum ) cultivar (‘Tota ́ l’) when grafted on a resistant cherry pepper ( C. annuum var. cerasiforme ) rootstock (cv. Szentesi). Resistance is manifested both towards PM symptoms and pathogen accumulation. In healthy, uninfected plants PM-resistance can be predicted by enhanced accumulation of the reactive oxygen species (ROS) superoxide (O 2 . 2 ) and activity of NADPH oxidase, the enzyme mainly responsible for pathogenesis-related superoxide generation. In L. taurica -inoculated PM-resis- tant ‘Szentesi’ high levels of superoxide and NADPH oxidase activity are sustained even 45 days after inocula- tion, as opposed to PM-susceptible ‘Tota ́ l’. This is also true for ‘Tota ́ l’ grafted on resistant ‘Szentesi’ rootstocks, where PM resistance, enhanced superoxide production and NADPH oxidase activity is likely due to an unknown, graft-transmitted signal. To further elucidate the mecha- nisms of graft-transmissible PM-resistance we monitored expression of pathogenesis-related (PR) genes in healthy and infected plants. In healthy plants, expression of CaPR - 1 is several times higher in leaves of PM-resistant pepper than in sensitive plants, while high expression of CaPR - 2 (glucanase) does not entirely correlate with PM-resistance, being detectable only in PM-resistant ‘Szentesi’. However, during advanced stages of PM-pathogenesis (45 DAI) expression of CaPR - 1 and CaPR - 2 is by far the highest in PM-susceptible ‘Tota ́ l’. Our results suggest that the direct biochemical cause of graft-transmissible PM-resistance in pepper is the enhanced accumulation of NADPH oxidase- generated superoxide. To our knowledge, this is the first report on the role of ROS (superoxide) in graft-transmis- sible, pathogen-specific disease resistance.

Actions (login required)

Edit Item