The effect of inoculation with an attenuated mutant strain of tobacco mosaic virus on the growth and yield of early glasshouse tomato crops

In trials in 1973-5 at the Glasshouse Investigational Unit for Scotland, the yield of fruit from tomato cv. Eurocross BB inoculated at the seedling stage with the Mil-16 attenuated strain of tobacco mosaic virus was 5–8-9-4% greater than that from uninoculated plants which became naturally infected with a severe indigenous strain of the virus within 7–8 wk of planting. The increase in fruit yield, particularly of better grades, resulted in higher gross financial returns (up to 25p/plant) from inoculated plants. The yields from the Mil-16 protected plants were up to 14% greater than those from plants artificially inoculated at the seedling stage with the indigenous severe virus. Inoculation with Mil-16 had little adverse effect on early growth or the rate of fruit development on the first five trusses, but in 1973 the final yield of inoculated plants was depressed c. 5% compared with that from plants substantially free from infection for 14 wk after planting. In 1 year's test no benefit from inoculation with Mil-16 was recorded in cv. Cudlow Cross.