Preliminary Study On Different Varieties Of Cotton Allelopathic Effect On Orobanche Spp.

In this study,43cotton varieties (lines) were used as donor plants, sunflower broomrape(Orobanche cumana) and small broomrape (Orobanche minor) were used as receptor plants.Hydroponic, pot and field experiments were conducted. Sunflower broomrape and smallbroomrape germination rates were applied for identification of different cotton variety’sallelopathic potentials.Hydroponic experiment was conducted to collect cotton root exudates, which was used togerminate small broomrape and lettuce seed germination. Cotton exist allelopathy effect toboth small broomrape and lettuce. There were significance difference of different varieties ofdifferent concentrations of root exudates induced to small broomrape and lettuce seedgermination. Small broomrape was a better receptor crop compared with lettuce.Pot experiment was conducted on fifteen cotton varieties and sunflower broomrape.Rhizosphere soil and cotton plant (root, stem and leaf) were obtained. The methanol andwater extracts induced the germination of sunflower broomrape seeds. The results showedthat the germination rate of cotton existed strain regularity. The germination rate of cottonroot extracts was higher than stem extracts and the germination rate of stem extracts washigher than leaf extracts. Furthermore, there was a significant linear correlation among therhizosphere soil, stem and leaf. The correlation coefficient was0.3622between rhizpspheresoil and stem extracts, the correlation coefficient was0.3070between rhizosphere soilextracts and leaf extracts, the correlation coefficient was0.5237between root extracts andstem extracts.Pot experiment was conducted to study on the effect between cotton and sunflowerbroomrape. Fifteen cotton varieties in seedling stage (two-leaf, four-leaf and six-leaf period)were obtained, of which extracts induced sunflower broomrape seeds germination, the resultsshowed that seedling of cotton in six-leaf stage performed the highest germination rate amongthe three stage. The effect of different cotton varieties on sunflower broomrape was similarwith the small broomrape. Field experiment was conducted to study on the effect of fifteen cotton varieties andsunflower broomrape. Cotton in growth period of root, stem and leaf methanol extractsperformed similar regulation with the pot experiment. The results showed that secondarymetabolites in root were more than in stem, and the stem was more than in leaf. The results ofthe pot experiment were further proved in the field experiment. The high concentration cottonroot extracts stimulating sunflower broomrapes with high germination rate and the lowconcentration of cotton root extracts with low germination rate. The methanol extracts ofcotton rhizosphere soil stimulating sunflower broomrape seeds with the highest germinationrate and the rates were stable in bud period. The root extracts which stimulating sunflowerbroomrape germination rates performed the highest in the six-leaf stage among the seedingstage, the stem and leaf extracts performed strong stimulation in the seeding stage generally.In conclusion, cotton rhizosphere soil and organs with high activity in the seeding stage.