Allelopathic effect of Plant extract from Ambrosia artemisiifolia on inhibition of Orobacnhe aegyptiaca seed germination and plant host interaction

Abstract

Orobanche species are a root holoparasitic plant lack of chlorophyll and completely depending on the host to complete their life cycle. They are classified as the most important parasitic plants in the world because of economic and financial losses in crops that may reach 100%. Due to the lack of sufficient information available to farmers, and the non-viability of traditional, chemicals and anti-herbicides to eliminate this herb. And also the possibility of killing the host plants instead of the parasitic one. For these reasons new biocontrol ways were developed. Ambrosia artemisiifolia plant leaf extracts can be a promising biocontrol herbicide. Because Orobanche seeds can stay dormant for long period, seeds were incubated for 7 days in dark to break their dormancy. During this period plant, leaves were collected and 10% (w\v) extract was prepared. Extract (10%) was experimented on seeds germination and using growth regulator (GR24) instead of root exudates. This step confirmed that Ambrosia artemisiifolia plant leaf extracts inhibited seed germination, while seeds with GR24 grew normally. Seeds were treated and incubated for 5 days with different extract dilutions (0.0, 0.5, 1.0, 1.5, 2, 2.5, 5 and 10%) to estimate their germ tubes length and to calculate 2 germination percentages, where germination percentages at 2.5%, 5 % and 10% were 0% without germ tube elongation, and the highest germination percentages were 94% at 0.5%, and other germination percentages were: 84% at 1%, 32% at 1.5% and 24%at 2%. Then different solvent were used to dissolve plant extract (water, ethanol, and methanol), water was detected the appropriated one where it completely inhibit seed germination. After comparing the effect of the pesticide (Chlorsulfuron) with the effect of the extract, it was found that the effects of the extract on preventing seed germination were higher than the effects of the pesticide, which proves that plant extract has a huge ability to compete with the chemical herbicides. To prove this, a potting experiment was conducted to study the effect of the extract (2.5% and 5%) on the germination of Orobanche seeds, in addition to studying its effect on the germination of model plant. It was noted that the extract had the ability to prevent seed germination by a percentage, but at the same time, it did not affect the growth of the model plant.