Tobravirus Isolation and RNA Extraction

The tobraviruses have a genome consisting of two positive-sense, single-stranded RNA molecules. The two genomic RNAs, RNA-1 and RNA-2, are encapsidated separately in rod-shaped particles with lengths of 180–215 nm (L particles) and 46–115 nm (S particles), respectively (Fig. 1 ) (1 ,2 ). Both the RNAs are encapsidated by a single species of coat protein (CP) with a mol wt of approx 23 kDa. Tobraviruses can be divided into three serologically distinct subgroups: tobacco rattle virus (TRV), which is the type member, pea early browning virus (PEBV), and pepper ringspot virus (PRV). In the field, these viruses are transmitted by soil-inhabiting nematodes of the family Trichodoridae , and certain isolates are also transmitted through the seed. Tobraviruses can infect a wide range of plant species including economically important crops such as potatoes and ornamental bulbs.