Researches On The Relationship Between Root Exudates Of Different Flue-Cured Tobacco Varieties And Resistant Of Black Shank Disease (Phytophora Parasitica Var. Nicotiana)

Four different varieties of flue-cured tobacco (Nicotiana tobacum L.) including Yun85(highresistance, HR), K326(middle resistance, MR), Jingyehuang(middle susceptibility, MS) andHonghuadajingyuan(high susceptibility, HS) were selected as experiment materials. Compositiondifference of phenolic acids and organic acids of root exudates of different flue-cured tobacco varietiesand correlation between the difference and varieties resistance were studied with solution culture,difference of rhizosphere microorganism in difference varieties were studied with pot culture, and effectof root exudates and phenolic acids on seedling growth were studied with imitating condition ofcontinuous cropping. And main results were as follows:1. Analysis condition of30%methanol-0.2%acetic acid system and phosphate system with reversedphase chromatography were suitable for qualitative and quantitative detection of phenolic acids andorganic acids of root exudates. These methods were convenient, high accuracy and goodreproducibility.2. Four phenolic acids were detected in different growth stage of different flue-cured tobacco varieties,and P-hydrobenzoic and syringic acid were main compounds. And there were difference in speciesand content for growth stage and vareties resistance. P-hydrobenzoic acid was less or none detectedin root exudates of resistance varieties and there was significant positive correlation between totalphenolic acids during whole stage and disease index. In addition, secretions of phenolic acids werepromoted after inoculation, and content of P-hydrobenzoic and syringic acid showed an increasingtendency in root exudates of difference varieties. Moreover, secretion of susceptible varieties wasgreater than resistant varieties, and there was significant or very significant positive correlationbetween P-hydrobenzoic, syringic acid and total phenolic acids and disease index. However, addingdifference phenolic acids had promotive or inhibitory effect on colony growth and sporangium yieldof phytophora parasitica var. nicotiana, and mode of action and strength depend on actionconcentration. And sporangium yield were all restrained by ferulic acid in each concentration andwere completely restrained by vanillic acid, coumaric acid and ferulic acid in high-concentration.Promotive effect of P-hydrobenzoic, syringic acid and coumaric acid and inhibitory effect ofvanillic and ferulic acid were greatly in same concentration. Zoopore release was mainly promotedby adding different phenolic acids, and the higher concentration, the action strength increase.3. Seven organic acids were detected in different growth stage of different flue-cured tobacco varieties,and oxalic, lactic and maleic acid were main compounds. And there were difference in species andcontent for growth stage and vareties resistance. Maleic acid of resistance varieties and lactic acidof susceptible varieties was mainly detected, and total organic acids of susceptible varieties werebigger than resistance varieties. In addition, secretions of organic acids were promoted afterinoculation and the inoculation time extension, the secretion increase. Detectable amount of organicacids of susceptible varieties were bgger than resistance varieties except tartaric acid. Total organic acids of susceptible varieties were greater than resistance varieties. Colony growths of phytophoraparasitica var. nicotiana were restrained by adding organic acids, and the higher concentration, theinhibitory increase. Sporangium yield and zoopore release were promoted or restained by addingmaleic acid, lactic and fumaric acid, and mode and strength of action depend on actionconcentration. While sporangium yield and zoopore release were restrained by oxalic acid, tartaricand succinic acid in each concentration, and were completed restrained by acetic acid.4. Mycelium growth of phytophora parasitica var.nicotiana were inhibited as well as mycelium growthand biomass liveweight by resistant cultivar root exudates, but mycelium growth and biomassliveweight were stimulated by susceptible cultivar root exudates in all stage. Meanwhile, exceptrapid growing stage, sporangium yield and release zoospore rate of other stage were stimulated bysusceptible cultivar root exudates, but sporangium yield were relatively small stimulated byresistant cultivar root exudates and release zoospore rate were inhibited in rapid growing stage. Sothe whole results show that different resistant cultivar root exudates are related to cultivar resistance.And stimulation of susceptible and inhibition of resistant cultivars focus on rapid growing stage andflower budding stage.5. Seed germination and seeding growth was obvious inhibited, chlorophyll content and root activityreduced, relative conductivity of leaves and root increased and pH value of root and rhizospheredecreased. And the negative influence was enhanced with concentration increasing. In addition,SOD, POD and CAT activity all presented trend of first increased and then decreased exceptkeeping hot activity and presenting increase trend all the time in leaves POD activity. Meanwhile,MDA content of leaves and root was increased.6. Germination percentage and seeding height were restrained by phenolic acid. And impact ofphenolic acid on above-ground FW and under-ground FW were difference for species andconcentration of phenolic acid. At the same time, total chlorophyll and root activity were inhibitedand pH, relative conductivity of root and MDA content were increased by treatment of phenolicacid. The effect of treatment on enzyme activity was difference. POD activity of root all presentedincrease at low concentration and then decrease at high concentration in different treatment ofphenolic acid. And SOD activity of treatment of vanilic acid and syringic acid respectivelypresented continue rise and down trend, other treatment all presented trend of fist increase and thendecrease. CAT activity were changed little at low concentration and then rapid promoted andmaintained high activity, and CAT activity of others presented trend of fist increase and thendecrease.7. Bacterial numbers of different cultivars are first increased and then decreased with the growingprocess, while fungal numbers are reverse. Meanwhile, the trend inflexions of bacteria and fungiare all happened at the flower budding stage, and that of actinomyces is relatively stable. There arepositive correlations between rhizosphere microorganism counts of bacteria and actinomyces and cultivar resistance, and a negative correlation between fungal number and cultivar resistance at therosette stage and the rapid growing stage. In addition, growth of bacteria is stimulated inrhizosphere environment of the resistance cultivars, while the growth is relatively restrained in thesusceptible cultivars. And growths of fungi and actinomyces are promoted in all experimentmaterials. The analysis results of the Biolog method show that there are some differences in totalutilization ability of carbon source and functional diversity in different growth stages of differentcultivars, and the average well color development (AWCD), Shannon index and Mclntosh index ofthe resistance cultivars are more than that of the susceptible cultivars in different growth stages ofdifferent cultivars. At the same time, AWCD values and functional diversity of the susceptiblecultivars are decreased after inoculating phytophora parasitica var. nicotiana.