Formulations of the endophytic bacterium Bacillus subtilis Tu-100 suppress Sclerotinia sclerotiorum on oilseed rape and improve plant vigor in field trials conducted at separate locations.

Sclerotinia sclerotiorum causes serious yield losses in crops in the People's Republic of China. Two formulations of oilseed rape seed containing the bacterium Bacillus subtilis Tu-100 were evaluated for suppression of this pathogen in field trials conducted at two independent locations. The pellet formulation significantly reduced disease (incidence and disease index) and increased plant dry mass, while the wrap formulation significantly reduced disease incidence and significantly increased plant dry mass at both field locations. Mean seed yield per 120 plants with both formulations of isolate Tu-100 was significantly greater than the appropriate controls, but at only one of the locations. Both formulations provided stable B. subtilis Tu-100 biomass (≥10(5) CFU·g(-1)) and seed germination (≥85%) over a 6 month period at room temperature. Polymerase chain reaction and DNA sequence analysis identified ituC and ituD, and bacAB and bacD in the genome of isolate Tu-100. These genes are involved in the biosynthesis of iturin and bacilysin. Iturin was detected in culture filtrates from isolate Tu-100, with thin layer chromatography. Detection of bacilysin was not attempted. Experiments reported here indicate the commercial viability of B. subtilis Tu-100 for suppression of S. sclerotiorum on oilseed rape.

Microsensor in vivo monitoring of oxidative burst in oilseed rape (Brassica napus L.) leaves infected by Sclerotinia sclerotiorum.

Oxidative burst is the rapid and transient production of large amounts of reactive oxygen species, including superoxide anion, hydrogen peroxide (H(2)O(2)), and hydroxyl radical. A rapid and simple technique was employed for in vivo detection of oxidative burst in oilseed rape (Brassica napus L.) leaves, using a modified electrode. Platinum (Pt) micro-particles were dispersed on a Pt electrode, coated with a poly (o-phenylenediamine) film. This exhibited high sensitivity, selectivity and stability in H(2)O(2) detection. Amperometry was used to obtain satisfactory linear relationships between reductive current intensities and H(2)O(2) concentrations at -0.1 V potential in different electrolytes. This electrode was used in vivo to detect oxidative burst in oilseed rape following fungal infection. Oxidative bursts induced by infection of the fungal pathogen Sclerotinia sclerotiorum (Lib.) de Bary exhibited notably different mechanisms between a susceptible and a resistant glucose oxidase-transgenic genotype.

Expressing a gene encoding wheat oxalate oxidase enhances resistance to Sclerotinia sclerotiorum in oilseed rape (Brassica napus).

Sclerotinia sclerotiorum causes a highly destructive disease in oilseed rape (Brassica napus). Oxalic acid (OA) secreted by the pathogen is a key pathogenicity factor. Oxalate oxidase (OXO) can oxidize OA into CO2 and H2O2. In this study, we show that transgenic oilseed rape (sixth generation lines) constitutively expressing wheat (Triticum aestivum) OXO displays considerably increased OXO activity and enhanced resistance to S. sclerotiorum (with up to 90.2 and 88.4% disease reductions compared with the untransformed parent line and a resistant control, respectively). Upon application of exogenous OA, the pH values in transgenic plants were maintained at levels slightly lower than 5.58 measured prior to OA treatment, whereas the pH values in untransformed plants decreased rapidly and were markedly lower than 5.63 measured prior to OA treatment. Following pathogen inoculation, H2O2 levels were higher in transgenic plants than in untransformed plants. These results indicate that the enhanced resistance of the OXO transgenic oilseed rape to Sclerotinia is probably mediated by OA detoxification. We believe that enhancing the OA metabolism of oilseed rape in this way will be an effective strategy for improving resistance to S. sclerotiorum.