TRANSMISSION OF TOBACCO RATTLE VIRUS ISOLATE PPK20 BY ITS NEMATODE VECTOR REQUIRES ONE OF THE 2 NONSTRUCTURAL GENES IN THE VIRAL-RNA-2

Tobacco rattle virus isolate PpK20 is transmitted by the nematode Para trichodorus pachydermus. RNA 2 of the virus determines vector transmis sibility and encodes the viral coat protein and two non-structural pro teins with molecular masses of 29 . 4 kDa and 32 . 8 kDa. Deletions an d a frameshift in the two non-structural genes did not interfere with encapsidation or co-replication of RNA 2 with RNA 1 after mechanical i noculation of plants. Mutations that affected the 29 . 4K gene or both non-structural genes abolished nematode transmission, whereas a large deletion in the 32 . 8K gene had no effect on transmission by P. pach ydermus. It is concluded that the 29 . 4K gene but not the 32 . 8K gen e is involved in transmission of isolate PpK20 by this vector.