Melon broomrape and sunflower broomrape seeds germination induced by hemp (Cannabis sativa L.) plants.
Rhizosphere soils and plant tissues (roots, stems and leaves) from hemp (Cannabis sativa L.) plants were collected under pot experimental condition to study their allelopathic effect on stimulating seeds germination for both melon broomrape (Phelipanche aegytiaca Pers.) and sunflower broomrape (Orobanche cumana Wallr.) at different growth stages. The results showed that rhizosphere soil extract displayed a higher germination rate for melon broomrape than that of sunflower broomrape. The seeds germination rates, induced by methanol extracts of roots were higher than that of stems and leaves. Induction of broomrape seeds germination by methanol extracts were stronger than that of aqueous extracts. There was a significant positive correlation between the germination rates of melon broomrape, which were induced by root methanol extracts and the stem extracts (R2=0.833 6, P<0.05). There was also a significant positive correlation between the germination rates of sunflower broomrape, which were induced by hemp root methanol extracts and the stem methanol extracts (R2=0.544 4, P<0.05). Methanol extract of the roots at seedling stage indicated the highest germination rate for sunflower broomrape seeds germination (45.2%), while melon broomrape seeds germination were appeared at fast-growing stage (41.5%). Aqueous extracts of hemp roots induced the highest germination rates on both melon and sunflower broomrape seeds at the seedling stage, with germination rates of 53.6% and 23.7% respectively. It is indicated that hemp has potential to be used as a "catch crop" for broomrape. These results can provide a basis for the bio-control of the parasitic weeds.