Sulphur Deficiency Causes a Reduction in Antimicrobial Potential and Leads to Increased Disease Susceptibility of Oilseed Rape

Abstract

The reduction of atmospheric sulphur dioxide pollution is causing increasing problems of sulphur deficiency in sulphur-demanding crop plants in northern Europe. Elemental sulphur and many sulphur containing compounds such as cysteine-rich antifungal proteins, glucosinolates (GSL) and phytoalexins play important roles in plant disease resistance. The aim of this work was to analyse the effect of inadequate sulphur supply on disease resistance of oilseed rape (Brassica napus). Compared with fertilized oilseed rape, healthy looking S-deficient plants showed increased susceptibility to the blackleg fungus Leptosphaeria maculans, to the generalist necrotroph Botrytis cinerea and to the oomycete Phytophthora brassicae. To analyse possible causes of the increased disease susceptibility of S-deficient plants, protein extracts and methanolic extracts of secondary metabolites of plants grown with and without adequate sulphur supply were tested for antimicrobial activity. None of the protein extracts showed antimicrobial activity. However, extracts containing secondary metabolites from normally grown plants showed a strong antimicrobial activity in in vitro tests with various fungal and bacterial pathogens. This activity was almost totally lost in extracts derived from S-deficient plants. The antimicrobial activity did not appear to be based on the activity of phytoalexins because it was present in healthy plants and was not increased by a previous inoculation with Botrytis cinerea. The loss of antifungal activity in S-deficient plants correlated with a strong reduction of various GSL, thus suggesting a reduced level of GSL as a possible cause of the reduced antimicrobial potential. However, limited tests of commercially available GSL or their degradation products did not demonstrate a causal link. Our results show that S-deficiency of oilseed rape negatively affects disease resistance and suggest that this effect is at least partially caused by a reduction of sulphur-dependent phytoanticipins.

Evidence for Proteomic and Metabolic Adaptations Associated with Alterations of Seed Yield and Quality in Sulfur-limited Brassica napus L

“…Even though the cultivar studied is a double low oilseed rape, GLS accumulation still strongly decreased in S-limited seeds, indicating that the GLS content in these seeds is principally regulated by their synthesis in pod walls during seed development, probably through a reduction in S supply and the regulation of S assimilation. The inhibition of myrosinase also highlights the importance of maintaining GLS in mature seeds, probably for its role in defense against pathogens, as demonstrated in leaves (44), which could be significant during germination or seedling establishment. We could then assume that S-limited seeds, particularly LS53 and LS32 seeds, are more susceptible to pathogen attacks.…”

Sulfur Nanoparticles Improves Root and Shoot Growth of Tomato

“…For plants sulfur is necessary in the formation of proteins, amino acids, enzymes, vitamins, and chlorophyll. Also sulfur helps the plant's resistance to disease (Cooper et al, 1996;Dubuis et al, 2005). Recently, great effort has been focused on finding approaches to synthesis sulfur nanoparticles (SNPs) with well-defined shapes and nano-sizes.…”

Defence mechanisms of Brassicaceae: implications for plant-insect interactions and potential for integrated pest management. A review

“…Oilseed Brassica species are also an important commodity in the world economy, as they are an important source of nutrition in developing countries (Rana, 2005). Amidst oilseed brassicas, oilseed rape has become a major crop in Europe, and one of the significant oil crops worldwide (Graner et al, 2003;Dubuis et al, 2005). The rapeseed and rapeseed oil production in 2007 from different countries that ranked in the first twelve worldwide are listed in Table I.…”