| The wheat sharp eyespot, caused by Rhizoctonia cerealis is a serious soil-borne disease which distributes widely in Huanghuai winter wheat area, northwest spring wheat area and the middle-lower regions of the Changjiang River. It has brought serious harm to wheat production. At present, there is no resistant variety available and the only way to control this disease effectively is chemical control with pesticide, which resulted in environment pollution and emergence of pesticide resistant strains. Therefore, it is necessary for us to find an alternative method to take the place of chemical protection. The usage of plant endophytic bacteria for biocontrol against the plant disease could overcome the shortage of chemical protection, and what's more important is the endophytic bacteria can exit in plant well,and control diseases stably, so it has more theoretical significance and applicable value.The main objective of this study were: to isolate endophytic bacteria from wheat and screen biocontrol bacteria that can control wheat sharp eyespot, analyse the characteristics and the colonization of these biocontrol bacteria.In this study, eight isolating media,including Beef extract Peptone Agar (BPA),Nutrient Agar (NA),Tryptic Soy Agar (TSA),Potato Dextrose Agar (PDA),Brain Heart Infusion (BHI),King's medium B (KMB),Luria—Bertani medium (LB) and Yeast extract Peptone Agar (YPA),were utilized to isolate endophytic bacteria from wheat,aiming at screening the optimal media.The results showed that the isolation effect of TSA and KMB was better than that of other media. Total 410 bacterial isolates were obtained from inner roots of 47 heathy wheat varieties in Henan province by the method of trituration and surface-disinfestation. The results suggested that both the endophtic bacterial species and the population density are differences between different varieties of wheat, and this is also the case with the same variety from different sources.At the same time, three isolates of the pathogen from sharp eyespot lesions of wheat in the field were obtained and identified with cell nucleolus staining as Rhizoctonia cerealis Vander. Comparing the pathogenicities among the three Rhizoctonia strains by pathogenic test for 61 different varieties of wheat, One strain of R.cerealis named Ry-3 with the serious pathogenicity, was selected as the pathogen for this paper.In the experiment, inoculation of pathogen with 1:30 (v/v)mixture of R.cerealis and soil has been examined as the best ratio, use the method of seed inoculation and soil drench to inoculate with the bacteria (concentration about 2×109 cfu / mL). On this basis, the system for screening of biocontrol strains in vivo was established. With this system 410 bacteria were tested for their ability to control wheat sharp eyespot. In the first screening, 62 bacterial isolates reduced the incidence of disease and the disease index, 37 of them had better control effects . When these 37 isolates were tested in a second screening, ten isolates had good control effeets with the values of 43.72 %(0-28)to 82.86 %(0-9. Then experiments were carried out to test the characteristics of these ten biocontrol strains, such as the mobility, produce enzyme or siderophore, antibiotic sensitivity, antagonism to pathogenic fungi et al. In the course of colonization study, found that five biocontrol strains could colonizate in the root of wheat, and 0-9 had the most colonization ability ( 1.4×105 cfu/g ), By physiological characteristics and the procedure of 16 s rRNA identifieation,the strain 0-9 belongs to Bacillus cereus.
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