The Effect of the Trichoderma harzianum Strains on the Growth of Tomato Seedlings

An experiment was performed with commercial and noncommercial Trichoderma harzianum strains to test whether they have any effect on the growth of tomato seedlings. The tomato (Lycopersicon esculentum Mill. cv. ‘Caruso’) seedlings were grown in a greenhouse and watered daily by hand. 18-day old seedlings were inoculated with Trichoderma harzianum strains Plantshield, T22, and T95 (10conidia plus mycelial fragments/ml) and transplanted into plastic pots filled with Pro-Mix potting mix. Randomized complete block design was used and treatments were replicated three times. At six weeks, the seedlings were sampled for growth comparisons on seedling emergence, number of true leaves, fresh and dry weights of roots and shoots, stem caliper and shoot height. The data were subjected to ANOVA and the means tested by LSD. The results demonstrated that Trichoderma harzianum strains improved tomato seedling growth. There were differences between the untreated control and the treatments for all of the growth parameters at 4 weeks after inoculation with the exception of root fresh and dry weight. INTRODUCTION Tomato is one of the most important vegetable crops in the U.S.A. According to the agricultural statistics in 1997, total area in which tomato has been grown is 185,353 hectares. Total production of fresh and processing tomatoes is approximately 13 million tons and the estimated value of production is $ 1.6 billion in 1996 (Anonymous, 1997). In tomato production, the U.S.A. ranks second in the world after China. Dollar value of the production could be much higher than the amount above if we can reduce the losses due to poor growing media, poor seedlings, plant diseases and the cost for chemicals to control diseases. Plant diseases, especially root diseases, cause significant losses in tomato production. For example, soil-borne plant pathogens cause seed rot, damping-off, root rot, wilt and fruit rot, which result in an annual $4-5 billion in the United States alone (Jewell, 1987). To remain competitive with the leading countries in tomato production, growers in United States must increase yields and offset production costs. Growing quality tomato transplants offers a number of benefits, in more economic production and convenience, to both commercial vegetable growers and home gardeners. To produce and market profitable crops, growers often depend on earliness, which can best be achieved by setting out well-grown and properly aged transplants. Transplant production in containers using potting media reduces plant mortality during field establishment and gives early and uniform crop yields (McKee, 1981). By using quality transplants, producers can insure a good stand of vegetable plants without the uncertainty of direct seeding (Courter et al., 1984). The fungus Trichoderma harzianum is a biological control organism against a wide range of soil-borne pathogens and has plant growthpromote capacity. It has been shown that T. harzianum stimulated the growth of tomato plants (Chet, 1990; McGovern et al, 1992; Datnoff and Pernezny, 1998). The purpose of current experiment was to determine the effects of Trichoderma harzianum strains on growth of tomato seedlings under greenhouse conditions Proc. XXVI IHC – Managing Soil-Borne Pathogens