1339 AJCS 10(9):1339-1347 (2016) ISSN:1835-2707 DOI: 10.21475/ajcs.2016.10.09.p7857 Growth-promoting activity of indigenous Trichoderma isolates on wheat seed germination, seedling growth and yield Behzad Hajieghrari 1 , Mohammadreza Mohammadi 2 1 Department of Agricultural Biotechnology, College of Agriculture, Jahrom University, PO BOX 74135-111, Jahrom-IRAN 2 Department of Plant Protection, Faculty of Agriculture, Varamin Branch, Islamic Azad University, Varamin, Tehran-IRAN *Corresponding author: bheghrari@yahoo.com; b.hajieghrari@yahoo.com Abstract Apart from their biocontrol potential, Trichoderma rhizosphere-competent strains stimulate plants growth via several direct mechanisms that affect various growth parameters. In this study, effect of five indigenous isolates (T. harzianum T 969, T. harzianum T 447, T. hamatum T 614, Trichoderma sp. isolate T and Gliocladium virens G525.) on wheat (variety Moghan 3) seed germination, seedling vigor and plant growth was examined through seeds treatment by the conidia and culture filtrate of the isolates. In the field experiments various growth parameters including rootlet and shoot length, stem height and weight, root length and weight, total leaf area, head and tiller number and 1000 grain weight as well as the plant total chlorophyll content and stomata conductance response were evaluated. In overall, seed germination rate was increased. The highest seed germination rate (95.8%) was observed for T. harzianum T969 non-sterilized cultural filtrate treatment and after 96 hours. The isolate G. virens G525 spore treatment decreased the rate by 54.5%. Although all isolates colonized on rootlets but no significant effect on the seedlings growth was observed. Isolate T. hamatum T614 caused necrotic reaction on rootlets, revealing its parasitic rather than symbiotic activity. In the field experiments, the isolates had significant effect on parameters such as stomata conductance, 1000 grain weight, ear fresh and dry weights, ear length and stem and root dry weight but they showed no significant effect on other evaluated parameters. Some isolates improved the affected parameters and some had negative effects which are discussed. Keywords: Trichoderma; wheat; seed germination; seedling vigor; plant growth. Introduction Agricultural soils around the world are under increasing pressure by input of huge amounts of chemical fertilizers to ensure crops high productivity and yield for growing human population. However, considering the many negative environmental and health consequences attributed to the use of inorganic fertilizers in agriculture and in order to achieve a sustainable and environmental-friendly agriculture, the use of such substances should be reduced and other eco-friendly and nature-based substances should be developed for improvements in the crops growth and yield (Gentili and Jumpponen, 2006, Hermosa et al., 2012, Bhardwaj et al., 2014). Biofertilizers are one of the environmental-friendly alternatives to the chemical fertilizers that are being marketed with the aim to increase the soils fertility and the crops productivity and yield without causing harmful environmental effects. These products also play important role in organic farming (Mihov and Tringovska, 2010, Hermosa et al., 2012). Biofertilizers are based on the microorganisms (fungi and rhizobacteria) that are able to colonize rhizosphere of the plants and promote plants growth and enhance their tolerance to the biotic and abiotic stresses via various mechanisms (Fuentes-Ramirez and Caballero- Mellado, 2005; Naganada et al., 2010). The fungus Trichoderma (Teleomorph: Hypocrea, an ascomycete), a ubiquitous fungus and common inhabitant of all soils and rhizospheres, and also common symbiont of the plants roots, has been an important component of biofertilizers (Vinale et al., 2014, Sharma et al., 2012). It is a biocontrol agent that beside antagonistic capabilities in suppression and control of soil-borne plant pathogenic fungi has also shown promising plant growth promoting potential (Harman et al., 2004, Druzhinina et al., 2011, Raats, 2012, Martínez-Medina et al., 2014). As an effective biocontrol agent, Trichoderma has been an important component of biofungicides with the aim to promote plants health avoiding the many negative effects of chemical fungicides on environment and human health (Lu et al., 2004, Topolovec-Pintarić et al., 2013, Maag et al., 2014). However, the results of investigations have highlighted the fungus abilities in enhancing plants growth independent from its antagonistic potential in suppression of plant pathogens (Contreras-Cornejo et al., 2009, Topolovec- Pintarić et al., 2013). Beneficial effects of Trichoderma as plant growth stimulator and promoter are attributed to several discovered mechanisms which include root colonization as endophyte symbiont, solubilization of the minerals and increasing availability of insoluble nutrients and therefore plant nutrient uptake, secretion of siderophores, plant growth regulatory materials (phytohormons), vitamins and enzymes (such as phosphate-solubilizing enzymes) (Anke et al., 1991, Benítez et al., 2004, Harman, 2006, Gravel et al., 2007, de Santiago et al., 2011, Li et al., 2015). The plant growth promoting activity of Trichoderma has been demonstrated in