INFLUENCE OF TRICHODERMA VIRIDE-INOCULATED GROWING SUBSTRATE ON THE GROWTH AND YIELD OF LETTUCE (LACTUCA SATIVA L.)

The effect of a rhizosphere-competent biocontrol agent – T. viride on the growth and yield of lettuce plants was investigated under the greenhouse conditions. A T. viride strain T6-RC isolated in the Department of Biochemistry, University of Tartu, was used to inoculate commercially produced fertilized peat. T. viride peat preparation was mixed with fertilized peat to obtain concentration of 10⁶ colony-forming units (CFU) per gram in growing substrate. Trichoderma increased the seedling emergence percentage and number of leaves, but did not affect fresh weight, dry matter content and total leaf area of transplants. Lettuce plants treated with Trichoderma had 43% longer roots compared to the control plants; at the same time average diameter of roots was smaller. The effect can be explained with the fact that plants from Trichoderma treatment had less roots with diameter over 1.5 mm and more roots with diameter up to 0.75 mm. Inoculation of growing media with Trichoderma increased also the average yield of lettuce plants at harvest.