The 2012 ASHS Annual Conference

Sorrel (Hibiscus sabdariffa var. sabdariffa L.), also known as ‘Roselle’, ‘Jamaican Sorrel’, or ‘Florida Cranberry’, is an annual plant belonging to the family Malvaceae.  It is cultivated in tropical and subtropical regions for stem fibers, paper pulp or edible calyces, leaves and seeds. Sorrel is an important crop in the Caribbean and South Florida, where traditionally the fleshy calyces are used for the preparation of a drink during the Christmas season. Dried calyces are exported from the Caribbean to West Indian communities in the UK and North America. Sorrel is grown as a fall and winter season crop because most lines are photoperiodic and induce flowers in October.  Over the past couple of years several sorrel producers on the island of St. Croix have reported a high mortality of plants in their fields. Plants wilted at any point during growth and production. Internally, conspicuous vascular discoloration was evident in these plants from the roots into the canopy.  Surface-disinfested 5 mm² infected sorrel pieces of vascular tissue plated on one-half-strength potato dextrose agar (PDA), produced salmon-colored fungal colonies. On banana leaf agar, single-spored strains produced the following microscopic characters of Fusarium oxysporum: copious microconidia on monophialides, infrequent falcate macroconidia and terminal and intercalary chlamydospores.  Sorrel seedlings were inoculated with isolates recovered from diseased plants by placing a mycelial plug (5 mm², PDA) over a small incision 5 cm above the soil line and then covering the site with Parafilm. Parafilm was removed after 1 week and plants were incubated under ambient temperatures (20 °C to 32 °C) in full sun for an additional 5 weeks (experiment 1) or 7 weeks (experiment 2). Compared with mock-inoculated (wound + Parafilm) control plants.  In addition, the DNA of Fusarium oxysporum isolates collected from diseased sorrel samples in St Croix is currently in storage.  The next step will be to generate partial, elongation factor 1-α (EF1-α) sequences and compare with those previously reported for this gene.