In vitro and in vivo antifungal activity of synthetic pure isothiocyanates against Sclerotinia sclerotiorum

Abstract

Sclerotinia sclerotiorum in the soil might be suppressed by the higher concentrations of allyl and benzyl ITCs released from decomposition of Brassica juncea, B. carinata, B. nigra and Sinapis spp.

Volatiles from biofumigant plants have a direct effect on carpogenic germination of sclerotia and mycelial growth of Sclerotinia sclerotiorum

“…sclerotia vs. mycelium. This variation in the ability of particular biofumigants to inhibit mycelial growth or carpogenic germination of S. sclerotiorum has also been observed by Kurt et al (2011) who found that different pure aliphatic and aromatic ITCs were effective against mycelial growth or carpogenic germination, but that the efficacy depended on whether they were used as vapour or contact phases. Aliphatic ITCs (derived from GSLs such as sinigrin, glucoerucin and glucoraphenin) were more effective than aromatic ITCs (derived from GSLs such as sinalbin) in the vapour phase, with the opposite being true when the ITCs were incorporated into PDA in contact phase.…”

“…juncea, was the most effective ITC in inhibiting carpogenic germination of S. sclerotiorum sclerotia (Kurt et al 2011). However, the HPLC analysis conducted here did not detect any GSLs in B. napus 'Temple', except for very small quantities of sinigrin.…”

“…Another relevant study examined the volatile effects of a range of pure ITCs on carpogenic germination of S. sclerotiorum sclerotia in vitro and showed that all of them with the exception of phenyl and 2-phenylethyl ITC at their lowest concentrations (42 and 34 µmol L −1 , respectively) significantly inhibited the production of apothecia over a period of 10 to 14 weeks (Kurt et al 2011). …”

“…GSL content can vary in the same crop grown in different years (Bangarwa et al 2011) and between tissues within a single plant, such as between leaves and seeds (Gupta et al 2012), or between leaves and flower buds. When a plant cell is ruptured as a result of pest or pathogen attack, or mechanical wounding, the GSLs and myrosinase come into contact and are hydrolysed in the presence of water to release various products, including isothiocyanates (ITCs) (Vig et al 2009) which have a wide range of biocidal characteristics (Kurt et al 2011) and are acutely toxic to several pathogenic fungi (Chew 1987). The definitive mode of action of ITCs inhibiting fungal growth and other microorganisms is uncertain, but some hypotheses include inactivation of intracellular enzymes by oxidative breakdown of sulphur bridges (Zsolnai 1966); inhibition of the coupling between the phosphorylation reactions and electron transport, therefore hindering the ATP synthesis (Kojima and Oawa 1971); inhibition of metabolic enzymes by the thiocyanate radical (Banks et al 1986); inhibition of Tumour Necrosis Factor proteins, involved in extrinsic apoptosis, or induction of intrinsic apoptosis, depending on the type of ITC (Molina-Vargas 2013).…”

“…For instance, Kurt et al (2011) found synthetic (pure) ITCs significantly reduced mycelial growth of S. sclerotiorum and sclerotial viability in vitro, with six of the seven ITCs tested providing complete suppression of sclerotial germination. B. juncea was found to be the only cruciferous plant tested to affect sclerotial viability of S. sclerotiorum in another study, delaying myceliogenic germination by seven days, although after ten days approximately 80 % of the sclerotia germinated (Smolinska and Horbowicz 1999).…”