Survey on alternative hosts of Corynespora cassiicola, the cause of the leaf and calyx spot, in the surroundings of roselle fields in Mexico

Corynespora cassiicola causes the leaf and calyx spot of roselle (Hibiscus sabdariffa) in Mexico. A survey was conducted to identify potential inoculum sources of this pathogenic fungus on cultivated plants and weeds in the main producing areas of roselle in Mexico. Identification of the fungus species was based on morphology and sequences of partial Actin and EF-1α genes. The fungus was found infecting Solanum lycopersicum, Chromolaena odorata, Senna alata, Hyptis suaveolens, Eugenia oerstediana, Passiflora viridiflora, Momordica charantia, Ricinus communis and Gossypium hirsutum. To our knowledge, all these plant species, with the exception of Solanum lycopersicum, are new records as hosts for C. cassiicola in Mexico, and the species Eugenia oerstediana and Passiflora viridiflora as new hosts worldwide. Pathogenicity tests showed that all C. cassiicola isolates of different plant species were able to induce lesions in roselle leaves and calyces. Disease management should include eradication of these alternative hosts.