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Plant Pathology

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 psohocarpi (Rac.) Gaumann., found on no plant genus other than Psophocarpus.

Synchytrium psohocarpi 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 Psophocarpus grandiflorus growing in Zaire, Uganda and Southern Ethiopia.

P. grandiflotus, Uganda
Synchytrium psophocarpi

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 Central Africa. This evidence was taken as additional support for the hypothesis that winged bean more closely resembles Psophocarpus grandiflorus than it does P. scandens.

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