Chemical Inactivation of Tobacco Mosaic Virus in Tobacco Seed.

Tobacco mosaic virus (TMV) affects all market classes of tobacco and is distributed worldwide.  The virus is localized in the nucellar layer of the tobacco seed coat and is recently demonstrated to be seed transmitted.  Chemical inactivation of TMV in the seed coat could reduce or eliminate seedling infection by the virus; thereby eliminating an early season source of primary infection.  The objective of these studies was to determine effective chemical treatments that eliminate seed transmission of TMV with no detrimental affects on germination.  Growth chamber experiments were conducted in a randomized complete block design with three replications.  Two tests were conducted twice and a third test was conducted four times.  Seed were collected from TMV infected and non-infected field grown ‘K 326’ flue-cured tobacco plants.  Presence of TMV was assessed by DAS-ELISA and biological activity was verified by infectivity assays on Nicotiana tabacum cv. Xanthi NN.  Treatment with 2% formaldehyde severely reduced germination by 97%.  Percent germination decreased with increased treatment time of the seed.  Presence of TMV in seedling samples was significantly reduced by 1% hydrochloric acid, whereas, trisodium phosphate and silver nitrate did not significantly reduce the number of TMV positive samples.  Most TMV positive seedling samples did not contain biologically active virus based on infectivity assays.  No chemical treatment eliminated TMV antigen in the seed coat of seed collected from a TMV infected plant based on ELISA, however, very few seed coat samples had biologically active virus based on infectivity assays.  These studies demonstrated that chemical seed treatments were effective in reducing, but not eliminating, seed transmission of TMV.