In 1992, a pycnidial fungus isolated from diseased amaranth plants was foun
d to be the causal agent of the observed stem and leaf blight. Inoculations
performed in the greenhouse revealed that this organism caused a disease c
haracterized by a general blight. The isolate was tentatively identified as
a member of the genus Phomopsis and its morphological characteristics were
compared to those reported in the literature for Phomopsis species collect
ed from amaranth. The Florida isolate, ATCC 74226, was found to produce ext
remely large alpha conidia. Beta conidia were produced, as well as a third
type of conidium of intermediate shape. Phylogenetic analysis, based on the
sequences within the internal transcribed spacer regions of the ribosomal
DNA, revealed that isolate ATCC 74226 differed substantially from the other
Phomopsis species tested, including those that are known to produce the th
ird type of conidium. Based on the morphological characteristics and DNA se
quence information the isolate is described here as a new species of Phomop
sis.