Effects And Mechanisms Of Crop Rotation Regime On Controlling Orobanche Spp.

Broomrape(Orobanche spp.)is a category of root parasitic weed that harms agricultural production in the world.At present,there is no method that can be used alone to effectively control the harm of root parasitic weeds in the long time and it is still a difficult operational problem about the control of broomrape.Among many control measures,the method of control broomrape by using the trap crops and host crops of broomrape in rotation has characteristics of recycled,safety and environmental protection,which can be effective to some extent in reducing the broomrape seed bank and the harm to crops,and this method,has attracted more and more attention.Xinjiang is one of most seriously area threatened by the Orobanche spp.in China.The Xinjiang Production and Construction Corps in Yanqi Agricultural Areas expect to reduce the harm of broomrape by planting sugar beets,wheat,peppers and host crop of Orobanche spp.in rotation,but the harm of Orobanche spp.is constantly increasing.At present,there is still a lack of scientific demonstration on the control effect and mechanism of this rotation regime,and there is no scientific guidance on the selection of crop rotation in practical production.According to different regions,climates and broomrape types,it is necessary to combine with the actual agricultural production to explore a better method.In this study,sunflower broomrape and Egyptian broomrape were selected as the control objects and the experimental materials were selected from the local cultivars in Yanqi Agricultural Areas.The seed germination assay in Petri Dishes was conducted to explore the germination effects of broomrape seed on the secretion of sugar beet,wheat and pepper.The simulated rotation pot experiment was conducted to demonstrate the control effect of the crop rotation in Yanqi Agricultural Areas on Orobanche spp.and the effect on the growth of the sunflower and processing tomato.In addition,the soil physical and chemical characters were also analyzed to explore the effects of crop rotation on control mechanism.The main conclusions of this study are as follows:(1)The tested varieties of sugar beet,wheat and pepper had the potential to control O.cumana,but could not stimulate the germination of O.aegyptiaca seeds.The tested varieties of sugar beet,wheat and pepper can effectively stimulate the germination of O.cumana seeds and had the potential to control O.cumana,but could not effectively stimulate the germination of O.aegyptiaca seeds.The results of seed germination assay: the root exudates,root exudates of ethyl acetate extract and aboveground methanol extract of sugar beet,wheat and pepper can effectively stimulate the germination of O.cumana seeds,but can not stimulate the germination of O.aegyptiaca seeds.The germination rates of O.cumana seeds stimulated by root exudates were all above 50.0%,and the germination rates of O.cumana seeds stimulated by aboveground methanol extract were all above 59.0%,among which the pepper "Qingdao xinlilai" had the best stimulation effect.However,the germination rate of O.aegyptiaca seeds stimulated by root exudates were all below 15.0%,and the germination rate of O.aegyptiaca seeds stimulated by aboveground methanol extract were all below 12.0%,which showed that there was no significant difference compared with negative control of distilled water.Therefore,the tested varieties of sugar beet,wheat and pepper had the potential to control O.cumana,but could not stimulate the germination of O.aegyptiaca seeds.(2)Experimental varieties of sugar beet,wheat and pepper can be added to the rotation system as the trapping crops of O.cumana to reduce the harm of O.cumana,but they cannot be included in the rotation system to control O.aegyptiaca.Experimental varieties of sugar beets,wheat,and peppers were rotated with sunflower,respectively.We found that the number of parasitic O.cumana on the sunflower were significantly reduced.There was no parasitic O.cumana on sunflower when sugar beet "0143" and pepper "Zijinshan" as a preceding crops in rotation with sunflower,so the control effect is most obvious.However,the the number of parasitic O.aegyptiaca on processing tomato reduced indistinctively and had no difference compared with control group after prodessing tomato rotated with these same varieties,so this crop rotation system could not control O.aegyptiaca effectively.Crop rotation significantly improved the growth of sunflowers and processing tomatoes.The maximum biomass growth rate of overground and underground parts of both sunflowers and processing tomatoes were more than 150.0%,and the maximum flower dish weigh of sunflowers were up to 123.1%.(3)Changes of soil physical and chemical character after rotation: Compared with the control group,the soil pH values were all decreased after the rotation.The soil pH value of the sugar beet "Ruima" and the pepper "Jinghong" reached 7.6 after the rotation,but the soil of pepper "Qingdao xinlilai" after the rotation showed acidity.Compared with the control group,the soil organic matter content,the soil nitrogen content and the soil available phosphorus of rotated soil were all increased after the rotation with these varieties.The increase of soil fertility and nutrients will further inhibite the germination of Orobanche spp.seeds in soil and contribute to the control the Orobanche spp.