Submitted to: Journal of Nematology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/29/2001
Publication Date: 2/1/2002
Citation: MOJTAHEDI, H., SANTO, G.S., THOMAS, P.E., CROSSLIN, J.M., BOYDSTON, R.A. ELIMINATING TOBACCO RATTLE VIRUS FROM VIRULIFEROUS PARATRICHODORUS ALLIUS AND ESTABLISHING A NEW VIRUS-VECTOR COMBINATION. JOURNAL OF NEMATOLOGY. 34:66-69. 2002. Interpretive Summary: Corky ringspot (CRS) is a devastating disease of potato that eliminates affected tubers from the market. CRS is characterized by arcs, concentric rings or diffuse extensive browning of tuber flesh that later dries into cork-like tissue, making the affected crop unsaleable. In recent years the disease has increased substantially in the PNW, which produces more than 50 percent of the potato crop in the U.S. In the Columbia Basin of Washington, more than 5,000 acres (representing $10 million in production costs) are now contaminated. CRS disease is caused by tobacco rattle virus (TRV), which is transmitted by Paratrichodorus nematodes. Although CRS may be controlled with Telone II fumigant (25 gal/A), which costs about $300/A, the control lasts only for one season. Alternative control measures should be developed that are both economical and safe to the environment. We have demonstrated in greenhouse experiments that TRV can be eliminated from the nematode by growing alfalfa or scotch spearmint. Although alfalfa and spearmint are hosts of the nematode vector, the nematode cannot acquire the virus from these crops. P. allius like other nematodes, molts four times in its life cycle, and loses its virus load after each molt when growing on a non-host plant free of TRV. Under greenhouse conditions, P. allius becomes virus-free after thriving on alfalfa or spearmint. We have also demonstrated the nematode can be reinfected with TRV and become viruliferous again by growing on plants that are hosts of TRV. Under field conditions, weeds in alfalfa and spearmint may serve as hosts for TRV and the nematode vector and may allow the TRV and nematode vector to persist in these crops.
Technical Abstract: We developed a reliable method to free viruliferous Paratrichodorus allius populations from native Tobacco Rattle Virus (TRV).This virus is vectored by P. allius in the Pacific Northwest and causes corky ringspot disease (CRS) on potato. The viruliferous nematodes that were reared on 'Vernema' alfalfa or '770' scotch spearmint for at least 3 mo could not transmit TRV to Samsun NN tobacco, a suitable indicator plant, and did not cause CRS symptoms on Russet Norkotah tubers. To introduce a new isolate of TRV to a virus-free population of P. allius, tobacco plants were first inoculated with a field population of viruliferous P. allius that transmitted TRV with distinct virulence on potato. The tobacco roots were then washed free from soil and dipped in 5.25 percent sodium hypochlorite to remove the initial nematode inoculum. After the bleached tobacco plants were recovered, the virus-free population of P. allius were introduced around the root system to acquire the new virus isolate from tobacco roots. The newly constructed virus-vector combination caused CRS symptoms on Russet Norkotah that were characteristic of the more virulent virus isolate, indicating that the virus-free P. allius population had become viruliferous again.