A potyvirus causing severe mosaic symptoms was isolated from Senna occ
identalis (syn. Cassia occidentalis) in the Yemen Republic and Ethiopi
a. It was transmitted mechanically and by Myzus persicae in a non-pers
istent manner. The flexuous, rod-shaped particles had a mean length of
830 nm, and pinwheels and scrolls were observed by electron microscop
y of thin sections of infected Nicotiana clevelandii leaves. Its host
range was narrow with only a few legume species, Nicotiana clevelandii
and N. benthamiana susceptible to experimental infection. This virus
was purified from N. clevelandii and the coat protein had a molecular
mass of 34.5 kDa. It reacted positively in ELISA With monoclonal antib
ody 197 that is specific for potyviruses, but was not decorated by ant
ibodies to any other potyvirus tested when examined by electron micros
copy. The virus has been tentatively named cassia severe mosaic potyvi
rus.