PURIFICATION AND PROPERTIES OF CLOSTEROVIRUS-LIKE PARTICLES ASSOCIATED WITH A WHITEFLY-TRANSMITTED DISEASE OF SWEET-POTATO

A virus causing sunken veins on 'Georgia Jet' sweet potato, and yellow brittle leaves and stunting on Ipomoea setosa, was purified and a spe cific antiserum was prepared. Flexuous particles with a normal length of 850 nm and a diameter of 12 nm with an open helical structure typic al of closteroviruses were observed. The virus particle protein has an apparent mol. wt of c. 34 kD. Double-stranded RNA isolated from SPSVV -infected I. setosa and subjected to electrophoresis in agarose consis ted of one major band with an estimated M(r) of 10.5 kbp and two minor bands with M(r) of 9.0 and 5.0 kbp. Fibril-containing vesicles in phl oem cells were observed in ultrathin sections of infected leaf tissues . The virus was transmitted by the whitefly Bemisia tabaci in a semi-p ersistent manner and by grafting, but not mechanically. The virus coul d be transmitted to various Ipomoea species, to Nicotiana clevelandii, N. benthamiana and Amaranthus palmeri. The virus did not react with a n antiserum to lettuce infectious yellows virus. Based on particle mor phology, serology and symptom expression, the virus appears unique and different from all other reported whitefly-transmitted closteroviruse s. We propose it be named ''sweet potato sunken vein virus'' (SPSVV).