Silicon-Induced Changes in Antifungal Phenolic Acids, Flavonoids, and Key Phenylpropanoid Pathway Genes during the Interaction between Miniature Roses and the Biotrophic Pathogen Podosphaera pannosa    

Abstract

Application of 3.6 mM silicon (Si+) to the rose (Rosa hybrida) cultivar Smart increased the concentration of antimicrobial phenolic acids and flavonoids in response to infection by rose powdery mildew (Podosphaera pannosa). Simultaneously, the expression of genes coding for key enzymes in the phenylpropanoid pathway (phenylalanine ammonia lyase, cinnamyl alcohol dehydrogenase, and chalcone synthase) was up-regulated. The increase in phenolic compounds correlated with a 46% reduction in disease severity compared with inoculated leaves without Si application (Si2). Furthermore, Si application without pathogen inoculation induced gene expression and primed the accumulation of several phenolics compared with the uninoculated Si2 control. Chlorogenic acid was the phenolic acid detected in the highest concentration, with an increase of more than 80% in Si+ inoculated compared with Si2 uninoculated plants. Among the quantified flavonoids, rutin and quercitrin were detected in the highest concentrations, and the rutin concentration increased more than 20-fold in Si+ inoculated compared with Si2 uninoculated plants. Both rutin and chlorogenic acid had antimicrobial effects on P. pannosa, evidenced by reduced conidial germination and appressorium formation of the pathogen, both after spray application and infiltration into leaves. The application of rutin and chlorogenic acid reduced powdery mildew severity by 40% to 50%, and observation of an effect after leaf infiltration indicated that these two phenolics can be transported to the epidermal surface. In conclusion, we provide evidence that Si plays an active role in disease reduction in rose by inducing the production of antifungal phenolic metabolites as a response to powdery mildew infection.

Identificación y alternativas de manejo de la cenicilla del rosal

“…Al respecto, Shetty et al (2012), reportaron que la aplicación de 3.6 mM de Si (100 ppm) suministrado en solución nutritiva, reduce la severidad de P. pannosa hasta un 48.9 % dependiendo del genotipo del hospedante, de igual forma Datnoff et al (2006), demostraron que la aplicación de Si reduce significativamente la severidad de la cenicilla hasta en un 57 % en rosas de maceta. Estos reportes sugieren que la aplicación de Si desempeña un papel importante en la supresión de la cenicilla del rosal, lo cual puede ser explicado por un incremento en la concentración de compuestos fenólicos antimicrobianos y flavonoides en respuesta a la infección por P. pannosa (Shetty et al, 2011).…”

“…Regarding this, Shetty et al (2012) reported that applying 3.6 mM of Si (100 ppm) in a nutrient solution reduces the severity of de P. pannosa in up to 48.9 %, depending on the genotype of the host, as Datnoff et al (2006), demonstrated that applying Si reduces the severity of powdery mildew significantly, in up to 57 % in roses in pots. These reports suggest that the application of Si plays an important part in suppressing powdery mildew in rose bushes, which could be explained by an increase in the concentration of antimicrobial phenolic compounds and flavonoids in response to the infection with P. pannosa (Shetty et al, 2011).…”

Silicon in plant disease control

“…These authors observed the complexation of phenolic compounds with silicon in the wall of epidermal cells so as to reduce and hamper the expansion of lesions and the disease intensity by making the cells more rigid, which was later confirmed by Rodrigues et al (2011). effect on disease reduction to the formation of both physical barriers, by deposition of Si (Sangster et al, 2001;Kim et al, 2002;Pozza et al, 2004;Carré-Missio et al, 2012b), and chemical barriers such as defense enzymes (Cherif et al, 1994;Fauteux et al, 2005;Cai et al, 2008;Shetty et al, 2011;Polanco et al, 2012). The joint action of these barriers in disease control in plants fertilized with Si was observed by Cai et al (2008) and Resende et al (2013).…”

“…Other crops such as strawberry, soybean, tomato and rose also showed promising results in reducing disease with Si application (Kanto et al, 2006;Carré-Missio et al, 2010;Lima et al, 2010;Ghareeb et al, 2011;Shetty et al, 2011). Conidia of Sphaerotheca aphanis var.…”

“…In its upward movement, via apoplast, from the roots to the leaves, silicon polymerization occurs in the extracellular spaces, accumulating on the walls of the epidermal cells of leaves and xylem vessels (Samuels et al, 1991;Fawe et al, 2001;Kim et al, 2002). There may also be increased activity of enzymes involved in plant defense such as peroxidase, polyphenoloxidase, phenylalanine ammonia lyase and lipoxygenase (Chérif et al, 1994;Fauteux et al, 2005;Cai et al, 2008;Shetty et al, 2011;Polanco et al, 2012), which, in this case, is considered as a chemical barrier. Therefore, Si application can contribute in the management of plant diseases, among other practices.…”