A NOVEL LUTEOVIRUS FROM SWEET-POTATO, SWEET-POTATO LEAF SPECKLING VIRUS

A virus obtained from accession DLP 1541 of the International Potato C enter (CIP) sweet potato germplasm collection was shown to induce a cu rling and a white speckling of the leaves of infected plants. We propo se to name it sweet potato leaf speckling virus (SPLSV). It was found in samples from 15 of 77 accessions tested and also in samples from fa rms at Chiclayo and Trujillo in northern Peru. SPLSV was transmissible by grafting, but not mechanically, and was transmitted in a persisten t manner by Macrosiphum euphorbiae but not by Myzus persicae, Aphis go ssypii or whiteflies. Isometric particles were purified from infected plants by procedures designed to purify luteoviruses. Reverse transcri ption and polymerase chain reaction amplification of RNA from SPLSV-in fected plants using degenerate primers designed to amplify sequences e ither in luteovirus RNA or in potato leafroll virus (PLRV) RNA yielded c. 500 bp and c. 600 bp DNA fragments respectively. The nucleotide se quence of these fragments encoded two polypeptides characteristic in s equence of luteovirus proteins, which suggests that SPLSV should be cl assified in the genus Luteovirus. The amino acid sequence of the putat ive coat protein was 70% identical to that of PLRV. On the basis of th e coat protein sequences, SPLSV is more similar to PLRV than is any ot her luteovirus. However, SPLSV particles did not react with antibodies to PLRV in ISEM or ELISA tests.