Effects of Trichoderma harzianum on the yield and fruit quality of tomato plants (Lycopersicon esculentum) grown in an unheated greenhouse

Trichoderma harzianum was applied to seedling growing media (a peat and soil-based mixture or greenhouse soil) at the time of sowing, at transplanting to vials and at planting. The factorial experiment using 2 seedling growing media, 2 cultivars and 4 dosages of T. harzianum at 0 (control), 4 g/m(2), 10 g/m(2) and 24 g/ m(2) showed that the Trichoderma dosage had no significant effect on the yield or fruit quality. None of the 3 factor interactions between the criteria studied, that is, total yield, marketable yield, early yield, individual fruit weight, total soluble solids and titratable acidity, were significant except for fruit diameter. The 3 factor combination of Peat x Belleveu F1 x 10 g/m(2) resulted in the highest total yield, marketable yield and early yield with 1552, 1373 and 681 g/plant, respectively. The interaction between media and cultivars was significant for all the yield characteristics studied. However, the main effect of T. harzianum on early yield was the highest at 4 g/m(2), producing 527 g/plant in comparison to the control with 374 g/plant. It was, therefore, hypothesised that the positive effect of T. harzianum, observed in the early yield, may be extended to the whole growing period by further applications, that is, by periodical renewal of the T. harzianum population at the root zone.