Studies On The Infection Process Of Burkholderia Glumae And Host Resistant Response To Bacterial Panicle Blight Of Rice

Bacterial panicle blight of rice(BPBR)caused by Burkholderia glumae is an emerging rice disease and threatens the high and stable-yield production of rice seriously.In this paper,the inoculation methods for resistant identification of rice to BPBR were tested.The bacterial population after seeds inoculation in different rice growing stages was measured.The infection process of B.glumae in roots,leaf sheaths,leaves and spikelets of rice was also observed.Meanwhile,the biochemical and physiological changes and the expression of defense response related genes were detected in both seedling stage and booting stage of rice.In addition,the inhibitory effect of some bactericides on B.glumae was tested.The main results were as follows:1.The optimal inoculation method for resistant identification of rice to BPBR was injection into panicle buds in booting stage,and the optimal concentration of bacterial suspension was 7×108 CFU/mL.The resistance of 15 rice varieties to BPBR was investigated by using the inoculation method of injection into panicle buds in booting stage.Results showed that Eyi 105,Wuyujing 3 and Shuhui 527 presented partial resistance to BPBR.Youyou 12,Mianhui 725 and Fuhui 838 were highly susceptible to BPBR.2.The results of detection on the bacterial population in different rice growing stages after seeds inoculation showed that B.glumae migrated from seeds into leaves,stems and panicles along with the growth of plants.The proliferation of pathogens at two-leaf stage and booting stage was the greatest during the growth period of rice.3.The result of observation on infecting process of the pathogen in rice roots,leaf sheaths and leaves inoculated with gfp labelled B.glumae showed that the pathogens entered vascular bundle through lateral roots and injured cells.The pathogens in vascular bundle laterally dispersed towards the epidermal cells and reached epidermal cells at 4-5 days after inoculation(DAI).The infection manner of the pathogens in leaf sheaths and leaves was similar.Leaf hairs and epidermal hairs were the initial infection sites.Pathogens could invade host through wounds or stomas,and then entered into adjacent vascular bundle.4.After panicles inoculation with gfp labelled B.glumae,the pathogens initially colonized in sterile lemma and the base of glume hairs.Bacterial population rose around glume hairs,broke into the palea and lemma,and spread into the gynoecium and stamens.Pathogens could also infect gynoecium and stamens through the crack of glumes.The spread in stamens mainly occurred through the connective tissue of anther,which caused the deformity of pollens.The SEM observation also confirmed that glume hair was the initial position for the colonization of pathogens.B.glumae broke into glume cells at 2-3 DAI.5.The TEM observation showed that the infection of B.glumae caused blurring of grana lamellae in chloroplast,and spinal core contusion in mitochondria of glume cells.The damage of the pathogens to ovary cells was mainly including the destruction of nuclear embrane and the autolysis of nucleolus.The infection of pathogens also caused empty and deformed pollens.6.The results of semi-quantitative and quantitative PCR detection showed that after inoculated with pathogens,the expression of resistance related genes(PBZ1、Rcht and PRIOb)were rapidly induced in both partially resistant variety and highly susceptible variety.And the expression of these resistance related genes was higher in partially resistant variety and booting stage of rice.The detection on the expression of genes related to systemic acquired resistance signaling pathways showed that the key enzyme gene PAL in salicylic acid signal transduction pathway was highly expressed in both two varieties.And the expression in partially resistant variety was higher than that in highly susceptible variety.However,the expression of key enzyme genes LOX and AOS in jasmonic acid signal transduction pathway was very low in both two varieties.It could be deduced that salicylic acid signal transduction pathway was mainly induced during the interaction between rice and B.glumae.7.After inoculated with pathogens in seedling stage of rice,the activities of O2·-and ·OH and the content of H2O2 in highly susceptible variety(Fuhui 838)were higher than that in partially resistant variety(Eyi 105),while the activities of antioxidant enzymes were lower than that in partially resistant variety.After inoculated with pathogens in booting stage,the activities of O2 " and ·OH and the content of H2O2 and antioxidant enzymes in highly susceptible variety were much lower than that in partially resistant variety.Compared with seedling stage,the increase of activities of O2 " and ’OH,content of H2O2,and activities of antioxidant enzymes in booting stage were earlier and stronger.8.Benziothiazolinone and zhongshengmycin showed relatively high inhibitory activity against B.glumae,with the EC50 value of 2.11 and 15.92 μg/mL,respectively.The mass ratio of 7:3 between zhongshengmycin and benziothiazolinone against the pathogen were the best ratio,with the EC50 value of 1.68 μg/mL.