Detection of Sclerotinia sclerotiorum in soybean seeds by conventional and quantitative PCR techniques

Sclerotinia sclerotiorum, the etiological agent of the "white mould" in soybean, is responsible for severe losses in this crop and soil contamination. The introduction and dissemination of the disease can made through the use of seed lots contaminated with sclerotia and by seeds infected by mycelium. Therefore, seed health quality is one aspect to be monitored by means of health testing before to sowing time. In this study conventional and quantitative PCR techniques were used to assess their viability to detect S. sclerotiorum in artificially and naturally infected soybean seed samples. For that, seeds were inoculated by osmotic conditioning technique for 0, 24, 48 and 72 hours of contact of the seed with the fungal colony and mixed with healthy seeds generating incidence levels of 1, 2, 10, 20 and 100% for each incubation time. The cPCR was sensitive to detect S. sclerotiorum in samples with at least incidence 1% inoculated for 72 hours while the qPCR detected the pathogen in all incidence/inoculum potential combinations. The conventional PCR was able to detect 0.25% of the incidence of S. sclerotiorum in soybean seed lots naturally infected added a preincubation step.