First report of sclerotinia stem rot caused by Sclerotinia sclerotiorum on Brassica carinata in Florida.
In late February 2012, symptoms typical of sclerotina stem rot were observed in Brassica carinata trials (cultivars 090867 EM and 080814 EM) at the University of Florida. Stems had white mycelia growing on the outside, plants were lodging and spherical to cylindrical, 3 to 8 mm, and black sclerotia were found outside and inside bleached stems. Fungal cultures consisting of white mycelia and medium-sized (mean 4mm), black, irregular sclerotia were consistently recovered and identified as Sclerotinia sclerotiorum based on morphological characteristics. Sequence analyses were conducted on mycelium by extracting fungal DNA. PCR amplification was performed using primers ITS1 and ITS4. The BLAST search revealed that the sequence (GenBank Accession No. JX307092) had 99 and 100% sequence identity with S. sclerotiorum (GenBank Accession Nos. JN013184.1 and JN012606.1). Pathogenicity was determined by inoculating six 1-month-old B. carinata plants that were grown in greenhouse pots. Symptoms similar to those observed in the field were evident after 3 days on inoculated plants and S. sclerotiorum was reisolated. This is thought to be the first report of sclerotinia stem rot of B. carinata caused by S. sclerotiorum in Florida.