Improvement of growth and yield of wheat in competition against the weeds in the ‎presence of mycorrhizal fungus

To investigate the effects of mycorrhizal fungus on competitive relations between wheat (Triticum aestivum) and weeds, two separated factorial experiments based on a completely randomized design were carried out at greenhouse conditions in Karaj, during 2017-2018. The factors of the 1st experiment were wheat and six weed species and two levels of mycorrhiza inoculation (with and without fungus) and that of the 2ndexperiment were pure stand of wheat, wild oat and rye and mixed cropping of wheat with wild oat and wheat with rye, and two levels of mycorrhiza inoculation (with and without fungus). In the 1stexperiment, mycorrhizal growth response of shepherd's purse (Capsella bursa-pastoris), bunchgrass (Phalaris minor), Londonrocket (Sisymbrium irio), perennial ryegrass (Lolium rigidum) and wheat were 18, 19.5, 23, 38 and 41 percentage, respectively and that of Rey (Secale cereale) and wild oat (Avena ludoviciana) were -29.28 and -22.40 percentage, respectively. In the 2nd experiment Rye and wild oat competition in non-fungus inoculated treatment reduced wheat dry weight by 41.58% and 51.4%, respectively. In the presence of fungus, wheat dry weight in competition with rye and wild oat, increased by 43.10% and 47.11%, respectively. In pure stand of wheat in the presence of fungus, wheat yield was 5.51 g/plant, which increased by 51.79% in comparison with non-application of fungus. The results of this research indicate that if the dominant weeds in the wheat fields, are non-mycorrhizal, or their mycorrhizal growth response is negative, the application of mycorrhizal fungi can reduce the damage of those weeds.