Drought, salinity and soil-borne fungi can constrain wheat establishment at the seedling stage. This greenhouse study examined whether Trichoderma viride improves wheat performance under separately imposed drought and salinity and limits damage associated with Fusarium infection. A four-factor factorial experiment was conducted in a completely randomized design with three replicate pots per treatment combination. The factors were three wheat genetic backgrounds, three pathogen treatments (a non-inoculated control, Fusarium oxysporum and F. graminearum), T. viride application (absence or presence) and three abiotic environments (a non-stressed control, salinity induced by 100 mM NaCl and drought maintained at 50% field capacity). Shoot dry weight, superoxide dismutase (SOD) activity and disease severity were measured. Drought imposes a greater limitation on shoot dry weight than salinity, with reductions of 36.6% and 25.3%, respectively. Across the tested environments, T. viride increases shoot dry weight by approximately 40% and raises SOD activity by 76.2% under salinity and 77.8% under drought. In Fusarium-inoculated plants, T. viride reduces disease severity by 46.2% for F. oxysporum and 69.2% for F. graminearum. Shoot dry weight, SOD activity and disease severity also differ significantly among the three wheat materials. Because each ploidy level was represented by a single material, these differences are interpreted as responses of the tested genetic backgrounds rather than independent ploidy effects. Under the conditions of this experiment, T. viride improved shoot growth and antioxidant activity while reducing Fusarium disease across the pathogen and abiotic environments examined.