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.