Comparison of allelopathic effects of Amaranthus retroflexus L. different organs extracts on germination and initial growth of Alvand and Zarrin wheat cultivars

Allelopathic effects of aqueous extract of pigweed, Amaranthus retroflexus L., different organs were evaluated on germination and initial growth of two common wheat cultivars (Alvand and Zarrin) in Iran. Experiments were conducted as factorial based on completely randomized design with three replications in laboratory and greenhouse of Islamic Azad University, Miyaneh Branch. Experimental factors comprised two wheat cultivars (Alvand and Zarrin), pigweed organs (leaf, root and stem) and concentration of aqueous extract of pigweed organs at three levels (2.5, 5 and 10%) and distilled water was considered as control. Traits including germination rate, plumule and stem length, fresh weight and dry weight of seedlings were measured. Results of variance analysis showed significant effects of experimental factors on all traits studied. Germination and initial growth of both wheat cultivars were affected by extracts of pigweed organs in all concentrations tested. Higher allopathic effects of pigweed extracts was observed on measured traits as extract concentration increased. According to the results, pigweed leaf extract was more toxic for wheat germination than extract of other organs. Leaf, stem and root extracts of pigweed reduced wheat germination up to 74%, 69% and 55% in Alvand and 67%, 50% and 49% in Zarrin, respectively. Based on the results, Zarrin was more tolerant to pigweed extracts than Alvand in germination. However, extracts caused the same statistical effect on growth related traits of both wheat cultivars at all tested concentrations. In conclusion, both Alvand and Zarrin were recognized as susceptible wheat cultivars to extracts of all weed organs, especially at higher concentrations (5% and 10%), and so, extension of their farming most probably may result in an increased yield loss duo to allopathic effects of pigweed.