In vitro antifungal activity of brassinin, camalexin and two isothiocyanates against the crucifer pathogens Alternaria brassicicola and Alternaria brassicae

Abstract

In vitro assays investigated the responses of Alternaria brassicicola and A. brassicae isolates towards two crucifer phytoalexins and two isothiocyanates (ITC) by evaluating their potential toxic effects on different fungal growth parameters. Although variable responses towards each compound was observed within the species A. brassicicola , the results obtained confirmed the antifungal effects of camalexin, brassinin, allyl-(AlITC) and benzyl-(BzITC) isothiocyanates, at different developmental stages of both Alternaria species. Irrespective of the tested isolate, the phytoalexin camalexin exhibited the greater inhibitory effect with mean EC 50 values ranging from 34 µ m (germ-tube elongation) to 183 µ m (mycelial growth). Germ-tube elongation was more sensitive compared to conidial germination and mycelial growth, with mean EC 50 values of the former of 81 µ m , 520 µ m and 870 µ m for brassinin, BzITC and AlITC, respectively.

Innate Immune Responses Activated in Arabidopsis Roots by Microbe-Associated Molecular Patterns

“…The best-characterized phytoalexin in Arabidopsis is camalexin, an indolic compound derived from Trp that is important for resistance against necrotrophic fungi such as Botrytis cinerea and Alternaria brassicicola (Thomma et al, 1999;Ferrari et al, 2003;Kliebenstein et al, 2005). In vitro, purified camalexin inhibits the growth of B. cinerea, Alternaria brassicicola, Alternaria brassicae, and P. syringae as well as the root pathogenic fungus Rhizoctonia solani (Rogers et al, 1996;Pedras and Khan, 2000;Ferrari et al, 2003;Kliebenstein et al, 2005;Sellam et al, 2007). In addition, camalexin is synthesized and exuded by Arabidopsis roots infected by the root-pathogenic oomycete Pythium sylvaticum (Bednarek et al, 2005).…”

Complex Genetics Control Natural Variation inArabidopsis thalianaResistance toBotrytis cinerea

“…In particular, the indole-derived phytoalexin camalexin contributes to A. thaliana resistance to the necrotrophic fungal pathogens such as B. cinerea and A. brassicicola (Thomma et al 1999;Ferrari et al 2003). These necrotrophic pathogens possess intraspecific variation in the inhibitory effects of camalexin on both conidial germination in vitro and pathogen growth in planta (Kliebenstein et al 2005;Sellam et al 2007). While genes responsible for several steps in the camalexin biosynthetic pathway have been identified, the signaling components required for induction of camalexin biosynthesis are relatively uncharacterized, although salicylic acid, glutathione, and reactive oxygen species all contribute ( Jirage et al 1999;Zhou et al 1999;Denby et al 2005;Qutob et al 2006;Nafisi et al 2007;Parisy et al 2007).…”

In Vitro Antioxidant and Anti-rhizopus Activity of Methanolic Seed Extract of Camelina Sativa L.

“…The first studied phytoalexin is a camalexin that was firstly isolated from the leaves of the crucifer C. sativa, which provides an exceptional model for the investigation of phytoalexins in defence responses 12 . Several in vitro studied showed the antimicrobial activity of camalexin against various pathogens [22][23] . Actually, camalexin disrupts cell membrane of bacterial and fungal pathogens 24 .…”