1978 Volume 44 Issue 4 Pages 504-508
L11A, an attenuated tomato strain of TmV which has been efficiently used for the protection of tomato plants against mosaic disease, proved to be inffective for protecting the existing TmV-resistant tomato cultivars having Tm-1 gene, possibly because the strain hardly multiplies in these cultivars, consequently the plants are readily infected by a virurent strain, e.g., CH2. For the purpose of obtaining another attenuated strain enough effective for protecting these cultivars, a new attenuated strain of TmV, L11A237, was isolated by successive passages of L11A through TmV-resistant GCR237 tomato (Tm-1/Tm-1). The new strain, alike L11A, causes no symptoms in tomato and Samsun tobacco, but differs in that it multiplies much faster than L11A in the existing TmV-resistant tomato cultivars (Tm-1/+) and sometimes causes necrotic rings on Xanthi nc in the environment in which L11A causes necrotic spots.
In cross protection tests in resistant tomato cultivars, L11A237 interfered more strongly with the multiplication of CH2, a virulent tomato strain of TmV infective to resistant tomato cultivars (Tm/+), than L11A did.
In the experiment in a plastic greenhouse the inoculation of resistant tomato seedlings (cv. Tanomo, Tm-1/+) by L11A237 resulted the good control of mosaic disease, and an higher yield than the yield of a plot which had not been inoculated with this attenuated virus.
In the plastic greenhouse of a tomato grower the effectiveness of L11A237 and L11A was compared using Tanomo tomato plants. The hundred-times diluted saps of L11A237-and L11A-infected tomato leaves were mixed with 1 per cent 800 mesh carborundum and inoculated to tomato seedlings at the distance of 10cm by working pressure of 5kg per cm2 with a motive sprayer. About 10 days later L11A237 and L11A garanteed 67 and 7 per cent infections and tomato plants inoculated showed mosaic symptoms of wild virus by 1 and 25 per cent after 5 months respectively.
These results indicate that L11A237 is very effective for the protection of the ordinary TmV-resistant tomato cultivars (Tm-1/+) from the infection by a virulent strain like CH2.