Study On Seedling Induction Mechanism For The Inhibition Of Sunflower Broomrape,Orobanche Cumana

Orobanche cumana is a complete parasitic plant,which has a serious impact on the production of sunflower.Jinmiao Target is a new kind of anti broomrape induced resistant agent.In this thesis,the optimal concentration and period for the application of Jinmiao Target.These perimeters were selected under laboratory conditions using petri dish and filter paper system.The effects of parasitic inhibition were verified by watering in pot.The inhibitory effect of Jinmiao Target on sunflower parasitism was studied in the field with drip irrigation.The optimum application period and concentration of Jinmiao Target for sunflower broomrape control under drip irrigation were applied.Finally,the inducer mechanism of different resistant cultivars of sunflower to Jinmiao Target was studied.The results of this research are as follows:1.Under laboratory conditions using petri dish filter paper system,the root system was irrigated before tubercles formation,the number of tubercles formed after 10 days showed that 1:500 dilution had the best inhibition effect with an average number of 2.33tubercles per dish.Compared with the control,the number of tubercles was 59,a decrease of 96.05%.The average number of tubercles per dish after watering 1:1000,1:2000,and 1:3000 dilutions showed a trend of decreasing inhibition rate with the increase in dilution multiples compared with the control.The results of root irrigation after tubercles formation showed that the best inhibitory effect was 1:500 dilution with88.56%reduction in the broomrape tubercles.The next treatment group was 1:1000,1:2000,1:3000 which decreased nodulation by 52.25%,47.14%and 43.24%respectively.The inhibitory effect of root irrigation of broomrape after young stems emerges differed between the 1:500 treatment group and the control group only.There were no significant differences between the other concentrations and control.The changes in the number of O.cumana after the above treatments were also confirmed by the statistical results relating to the browning rate of O.cumana.The browning rate of O.cumana was seen to increase with different treatment concentrations,but the 1:500 treatment concentration had the most obvious effect.Due to cost and high dilution concentration which turned new leaves brown or dead after root irrigation,it is recommended to use 1:2000 dilution concentration for treatment before the formation of tubercles.2.Based on the above results,the effect of Jinmiao Target on the inhibition ofseedlings of sunflower broomrape parasitism was studied under greenhouse conditions.Compared with the control,the number of tubercles decreased by 95.5 after treatment with LD5009+Jinmiao Target,the fresh weight and dry weight of tubercles decreased by 0.35 g and 0.08 g respectively.The height and stem diameter of sunflower increased by 2.09 cm and 0.52 cm respectively.However,the number of tubercles in JK103+Jinmiao Target reduced by 37.5,the fresh weight and dry weight of tubercles decreased by 0.33 g and 0.043 g respectively.The height and stem diameter of sunflower increased by 2.07 cm and 0.39 cm respectively.There were significant differences between the two treatment groups and the control groups.3.Under field conditions combined with drip irrigation,the application of Jinmiao Target and biocontrol agent（Bacillus subtilis chitin）inhibited the parasitic effect of broomrape.The parasitism rate of broomrape after using Jinmiao Target and Jinmiao Target with B.subtilis chitin decreased by 38%and 27.34%respectively,compared with the control,parasitism also decreased by 4.03 and 7.21 respectively.After application of B.subtilis chitin complex alone little effect was seen on the number of broomrape parasites.The growth and yield indexes of sunflower under Jinmiao Target,Jinmiao Target and B.subtilis chitin complex under drip irrigation were significantly higher than those under water irrigation.4.In this thesis,the mechanism of the inhibition of broomrape on sunflower JK103and LD5009 was studied under greenhouse conditions.The results showed that after root irrigation,the content of H₂O₂after 24h reached the maximum,3.53μmol/g and2.68μmol/g respectively.The most significant increase was recorded in the susceptible variety LD5009,an increase of 208.05%.After irrigation the corpus callosum deposition in the roots was increased.However,the JK103 showed the most significant increase after 48h.The activities of four different ROS scavenging enzymes（SOD,CAT,POD and PPO）showed an initial trend of increasing and then decreasing after treatment.The maximum value was reached at 48h after treatment,the maximum values were 69.77U/g,5.44U/g·min,1.88U/g·min and 527U/g·min respectively.Transcriptional analysis of related resistance genes indicated that the resusceptible variety was induced in different degrees after target treatment.However,induction degree of LD5009 with Jinmiao Target was the most obvious,especially CAT.Mn-SOD and XTH6.The relative expression levels were more than 50 times higher than the control.