Now, University of Illinois researchers have developed two techniques to determine whether these spores are viable.
The first technique uses two dyes: carboxyfluorescein diacetate and propidium iodide. Viable spores stain green with CFDA; non-viable spores counterstain red with PI. The second technique uses a two-color fluorescent viability probe that causes cylindrical vacuolar structures to form within living spores, which then fluoresce red
. Non-viable spores show only faint fluorescence. Soybean rust, which first appeared in Japan at the beginning of the 20th century, is a foliar infector that reduces plant photosynthetic activity and causes defoliation, premature death, and high yield loss.
An obligate pathogen, it grows only on plants and dies when the plant dies or is harvested. The fungus is concentrated in the southern states where it is able to overwinter on kudzu.
USDA Agricultural Research Service scientist and crop sciences professor Glen Hartman, Ramya Vittal, a postdoctoral researcher in the Laboratory for Soybean Disease Research, and James Haudenshield, a USDA-ARS research plant pathologist did the development work.