Heuchera root rot, a new disease for Plectosphaerella cucumerina

Abstract

AbstractA Plectosphaerella sp. was isolated from an undescribed root rot of the herbaceous ornamental Heuchera sanguine (Coral Bells) in Massachusetts. Morphological examination and phylogenetic analysis using DNA sequences derived from internal transcribed spacer (ITS) of rDNA, large subunit (LSU) of rDNA, calmodulin (CaM), β‐tubulin 2 (Tub) and transcription elongation factor 1 (Ef‐1α) loci identified the fungus as a member of Plectosphaerella cucumerina. A test of Koch's postulates on an isolate of P. cucumerina indicated that it was a pathogen causing root rot in Heuchera sp. The pathogen caused greatest damage to small transplants (1–4 g) as opposed the larger transplants (9–13 g) and in separate studies was found to infect seedlings of cucumbers, melons and pumpkins. Plectosphaerella cucumerina is reported for the first time in Heuchera sp. Given the importance of Heuchera to the ornamental industry, and the rapid dissemination that can occur with propagated material in the horticultural trade, caution should be exercised to prevent the spread of P. cucumerina.