Serenomyces associated with palms in southeastern USA: isolation, culture storage and genetic variation

Serenomyces is a genus belonging to the family Phaeochoraceae, which is known to occur only in association with the plant family Arecaceae (palms). It is presumed to be one of the causes of a leaf disease referred to as either rachis blight or petiole blight, depending on the palm species affected. The fungus is not readily observed, with few reports in the literature; it cannot be readily isolated from tissue, with only one known instance of it being cultured on artificial media and has no DNA sequences deposited in GenBank. Over an 8 y period, leaves symptomatic for rachis or petiole blight were obtained from Florida and South Carolina, USA. The fungus was induced to produce ascospores, and single-spore isolates were obtained in culture and, in some instances, induced to produce ascospores in culture. Based on ascospores size and ITS sequencing, Serenomyces from Phoenix canariensis and P. dactylifera form one group, Serenomyces from Thrinax radiata form a second group and Serenomyces from Sabal palmetto form a third. All three groups are most similar morphologically to Serenomyces phoenicis. Due to the observed instability of Serenomyces in culture, we have suggestions regarding the storage of this fungus.