Identification Of Sources Of Resistance To Orobanche Aegyptiaca In Xinjiang 31 Muskmelon Varieties And Resistance Mechanism Of Resistant Varieties

Objective: According to that parasitic Orobanche aegyptiaca for different resistance of muskmelon?s growth,physiological and biochemical effects and organizational structure,identify the resistance level of Orobanche aegyptiaca resistant on 31 varieties of muskmelon in Xinjiang.Analysis the resistant mechanism of resistant and parasitic varieties of the Orobanche aegyptiaca.Provide reference for planting rational distribution of varieties and Orobanche aegyptiaca-resistant breeding.Method: Rhizotron,pot,and field experiments were performed to evaluate the resistance of 31 selected muskmelon varieties in Xinjiang to Orobanche aegyptiaca population.By using field plot test,determining the impact of plant morphology,biomass and biomass distribution pattern to different resistance of muskmelon,when Orobanche aegyptiaca be parasitized.By using Rhizotron test,determining the changes of root ROS and protective enzyme activity for different muskmelon varieties when Orobanche aegyptiaca be parasitized.Using the technique of tissue cytology and different staining methods,analysis the relationship of resistant and parasitic Orobanche aegyptiaca on varieties of muskmelon and its organization structure relationship.Results:1.1.Only the ?Jintianmi17? contain the resistance to Orobanche aegyptiaca.In rhizotron experiments,the notable developmental arrest of the inoculated seedlings during stage Ⅱ of Orobanche aegyptiaca seeds,was observed in ?Jintianmi17?.In pot and field experiment,Orobanche aegyptiaca parasitism rate on ?Jintianmi17? was 33.33% and 50.00%,the parasitic degree was 0.33 and 1.67.There were 4 melon cultivars such as ?Yazhoumi17?in the second category,which had a tolerance to Orobanche aegyptiaca.In rhizotron experiments,the notable developmental arrest of the inoculated seedlings during stage Ⅲ of Orobanche aegyptiaca seeds,was observed in 4 melon cultivars.In pot experiment,the parasitism rate of Orobanche aegyptiaca on these four varieties was 71.43%~75.00%,parasitic degree was 1.29~4.25.The other 26 muskmelon varieties were sensitive to the broomrape.In rhizotron experiments,which did not inhibit the normal growth of broomrape.In pot and field experiment,the highest Orobanche aegyptiaca parasitism rate on 26 muskmelon varieties were 100%,and the highest parasitic degree were 13.00 and 17.50 respectively.2.The effect of parasitism on the root length of muskmelon was the greatest.The susceptible varieties,?Naxigan? is 52.18% less than the control;the resistance variety,?Jintianmi17? is 21.53% less than the control.Moreover,the greatest impact for muskmelon is root biomass,less effect for muskmelon is leaf biomass.The impact of biomass for ?Naxigan? was higher than that of ?Jintianmi17?.Orobanche aegyptiaca infection could cause changes in Muskmelon biomass distribution pattern.When the muskmelon is be parasitized by Orobanche aegyptiaca seeds,resistance variety,?Jintianmi17?,which root-top ratio decreased by 12.50% compared with the control;the susceptible varieties,?Naxigan?,which root-top ratio decreased by 37.30% compared with the control.3.When be parasitized by inoculated seeds of Orobanche aegyptiaca,the susceptible varieties,?Naxigan?,whose ROS and MDA content increased significantly;the resistance variety,?Jintianmi17?,whose ROS and MDA content rising slowly and below the sensibility.At the same time,the activity of antioxidant enzymes increased significantly in the resistance varieties.The activities of POD,SOD and CAT in the resistant varieties were all higher than those of the sensibility varieties,which indicated the degree of activation of the ROS scavenging mechanism may determine the resistance of Muskmelon.Furthermore,when Orobanche aegyptiaca infected,the PAL activity in ?Jintianmi17? is higher than ?Naxigan?,which indicated lignin accumulation may also contribute to muskmelon resistance to Orobanche aegyptiaca.4.Through paraffin section observation,it was found that the density of cortex cells in root cortex of resistant melon variety ?Jintianmi17? was higher than that of ?Naxigan?.In qualitative experiment,there were obvious phenomena of lignin and phenolic deposition in root system of resistant cantaloupe.In quantitative experiments,the content of lignin and phenols in resistant varieties was higher than that in susceptible varieties.These structural differences and morphological changes may be one of the ways to resist and delay the invasion of Orobanche aegyptiaca.