Fungitoxic effect of scopolin and related coumarins on Sclerotinia sclerotiorum. A way to overcome sunflower head rot

Abstract

The content of coumarins, as probable phytoalexins, was analysed in four sunflower genotypes that ranged in responses to head rot from highly susceptible to highly resistant. Low levels of all coumarins (scopolin, scopoletin and ayapin) were detected in the three most susceptible genotypes irrespective of time after inoculation. However, in the resistant genotype there was a clear time-dependent disease-induced increase of all coumarins that reached a maximum after 10-14 days. Detailed comparison of the most susceptible and the resistant genotype showed that in the resistant but not the susceptible, scopoletin peroxidase activity increased during the course of the experiment. Results confirmed a clear negative correlation between coumarin content and disease symptoms and in particular for scopolin. Furthermore we show for the first time that scopolin is inhibitory to Sclerotinia at similar doses to scopoletin. As scopolin is known to be less phytotoxic than ayapin and scopoletin, its accumulation may well confer head rot resistance with minimal plant damage and might be one of the bases for resistance to Sclerotinia.Abbreviations: EMT, esculetin methyl transferase; SGT, scopoletin glucosyl transferase; SP, scopoletin peroxidase

Effect of extracts from in vitro-grown shoots of Quillaja saponaria Mol. on Botrytis cinerea Pers.

“…The preliminary analysis by HPLC shows that in vitro quillay ethanolic extracts contain a series of secondary metabolites (Table 1), which have been reported as antifungal compounds on phytopathogenic fungi, such as saponins (Oleszek et al 1990;Osbourn et al 1996;Apablaza et al 2002;Chapagain et al 2007), and the phenolic compounds chlorogenic, caffeic, vanillic, and salicylic acids (Derek et al 1989;Harborne and Baxter 1993;NitaLazar et al 2004;Prats et al 2006), and the coumarin scopoletin (Uritani and Hoshiya 1953;Minamikawa et al 1992Minamikawa et al , 1964Murray et al 1982;Tanaka et al 1983;Gutiérrez et al 1995;Prats et al 2006). These results suggest that the antifungal activity of in vitro quillay culture could be explained, at least partly, by the presence of saponinas and phenolic compounds.…”

Benzothiadiazole and BABA improve resistance to Uromyces pisi (Pers.) Wint. in Pisum sativum L. with an enhancement of enzymatic activities and total phenolic content

“…Previously, there has apparently not been any report of BABA impairing the early stages of fungal development. Inhibition of the early stages of fungal development has been associated with the excretion of specific antifungal plant metabolites, including phenolics, to the leaf surface that interfere with fungal development (Prats et al 2006). Phenolics have been shown to play an Greek letters within a solid bar indicate significant differences (p <0.05) within the inoculated plants.…”

“…Penetration resistance is a key component of basal defence against pathogens and is associated with cell wall strengthening and specific development of papillae (cell wall appositions) under the site of attempted penetration (Hückelhoven 2007). Formation of cell wall appositions is achieved following signal transduction pathways, rapid reorganization of actin microfilaments, actin dependent transport of secretory products to the infection site and local activation of callose synthesis (Prats et al 2006;Hardham et al 2007). …”

“…Activity of total soluble peroxidase and scopoletin peroxidase were determined by measuring the appearance of pink/brown colour resulting from scopoletin oxidation in the presence of hydrogen peroxide at 470 nm (Prats et al 2006). Briefly, leaves were homogenated in Tris-HCl buffer (0.1 M, pH 7.4) 1:1 (v/w) with 30% of PVPP.…”

Analysis of Differential Transcript Expression Reveals Time-Dependent Leaf Responses to Sclerotinia sclerotiorum in Wild and Cultivated Sunflower

“…The role of phenolic and hydroxycinnamic acids in HelianthusSclerotinia interaction has been shown previously (Bazzalo et al 1985;Hemery-Tardin et al 1998;Prats et al 2003;Rodriguez et al 2004). Also coumarins have been mentioned to play a crucial role in pathogen defence and resistance to S. sclerotiorum in sunflower (Tal and Robeson 1986;Urdangarin et al 1999;Prats et al 2006). The upregulation of CCL at dpi 2 in the resistant genotype possibly contributes to the production of an increased pool of antifungal phenolic substances having an inhibitory effect on growth of the pathogen during early stages of pathogenesis.…”