Plant pests and diseases can give clues to
plant origins. An important disease of winged bean is the false
rust caused by the fungal organism Synchytrium
Gaumann., found on no plant genus other than Psophocarpus.
has been recorded on winged bean in Papua
New Guinea, Indonesia, Philippines, Malaysia, and to a minor
extent in Bangladesh, but not in Myanmar or India. Some Indonesian
varieties tested in Bogor, West Java, have been shown to have
genetic resistance to false rust, but all other varieties tested,
appear susceptible to the disease.
In 1987, and again in 1988, symptoms of false
rust were observed on widely dispersed natural populations of
growing in Zaire, Uganda and Southern Ethiopia.
Symptoms of false rust visible
on the leaves of Psophocarpus
grandiflorus in Lake Bunyonyi,
South West Uganda.
Subsequent tests suggested the strong likelihood
that this false rust was caused by the same organism Synchytrium
psohocarpi responsible for false rust in winged bean.
The interesting thing about this, was that no symptoms of false
rust were observed on P. scandens populations
growing in similar locations in
Africa. This evidence was taken as additional support for the
hypothesis that winged bean more closely resembles Psophocarpus
grandiflorus than it
does P. scandens.