Ergosterol as a Quantifiable Biomass Marker for
Diaporthe phaseolorum and Cercospora kikuchii.
H. Q. Xue, Crop Science Department, North Carolina State University,
Raleigh 27695; R. G. Upchurch and P. Kwanyuen, USDA-ARS Soybean and
Nitrogen Fixation Unit, Raleigh, NC 27695. Plant Dis. DOI:
10.1094/PD-90-1395. Accepted for publication 2 June 2006.
The ergosterol assay detects and quantifies the fungi-specific sterol
lipid molecule, ergosterol. We determined that the ergosterol assay could
be used to measure the extent of soybean seed colonization by Diaporthe
phaseolorum and Cercospora kikuchii. Ergosterol was shown to be
a reliable biomass marker for both fungi, since it was found to be highly
linearly correlated with fungal dry mass. Thus, ergosterol content was
positively correlated to the amount of pathogen colonizing experimentally
infected seed. Using the ergosterol assay, we determined that soybean
varieties differed with respect to the extent of seed colonization by
these fungi. Our results suggest that ergosterol content can be used to
quantify D. phaseolorum and C. kikuchii colonization of
soybean seed and that the method has potential to detect variety
differences in seed susceptibility to these two pathogens.
