As new sources of resistance genes are
identified to rust caused by Uromyces appendiculatus, we
need to know if these genes or others incorporated in the bean
germplasm will become susceptible to the pathogen when the
resistant varieties are widely grown. We have used a mobile
nursery of bean lines/varieties with different rust resistance
genes to answer this question. This nursery, composed of sixday-
old bean plants, is placed in a rusted bean field for two to
three hours, misted for 15 hours in a controlled environment
and incubated in a screened house for eight to ten days.
Readings for rust uredinia (pustule) size on the plant leaves
are then recorded. Data on disease reaction can be used to
evaluate the pathogen virulence and predict gene deployment
pathotypes by inoculation in the greenhouse and allows
results to be known during the growing season as opposed to
a few months later. The mobile nursery concept may be
especially useful in countries where greenhouses are rare and
may be used in other crop-pathogen systems.