Isolation,Identification And Functional Study Of Endophytic Bacteria In Oat

Oat,a crop used for food and feed,Avena sativa has cultivated for thousand years and been extending in past 10 years for many government policies,such as the adjustment of the agricultural structure,the husbandry development,and construction of ecological environment.As a result,oat diseases has been more and more serious.Chemical control would cause "3R" problems.The sustainable agriculture need ecology friendly method for pest control.Plant endophyte has become a research focus as important resource in many area,such as botany,microbiology,plant protection and crop breeding.In this study,endophytic bacteria of oat were isolated by dilution coating method.The antagonistic activity and capacity of promoting growth of endophytic bacteria in oat were studied.This study provided key resource for biocontrol to oat pest,and was important foundation for antifungal mechanism research,further.The main research results were as follows:1.A total of 512 endophytic bacteria were isolated from 52 oat samples in different sites,of which 9 bacteria strains significantly inhibited mycelium extending of Colletotrichum graminicola and Drechslera avenae causing oat leaf spot,as well as many potato fungal pathogens.YN-J3 was most potential on inhibiting mycelium extension.The strains was identified by Morphological,physiological,biochemical and molecular methods.The strains JN-Y2(OM019197),XH-J8(OM019198)and ZZ-G2(OM019202)were identified as Bacillus velezensis;strains JN-G7(OM019199)and JN-J12(OM019200)were identified as Bacillus subtilis;strains YN-J3(OL872222)and ZZ-J4(OM019201)were identified as Bacillus amyloliquefaciens;strain ZZ-G5(OM019203)was identified as Bacillus atrophaeus;strain ZZ-J3(OM019204)was identified as Bacillus thuringiensis.2.The bioassay results of the 9 strains showed that B.amyloliquefaciens YN-J3 had prevented occurrence with control effect of 75.27%,followed by strain JN-Y2 with a control effect of 66.66%.In addition,B.amyloliquefaciens YN-J3 promoted the growth of oats,and its oat height increased by 24.84% compared with the control.Followed by the strain YNY2,plant height increased by 24.41%.In field,the oat height treated with B.amyloliquefaciens YN-J3 was significantly higher than control at both experiment lacations,Jining and Wuchuan.Disease index of leaf spot decreased by 59.44% and 68.41%,respectively.And disease index of oat anthracnose decreased by 74.53% and 63.57%,respectively.3.We analyzed the biochemical characteristic of endophytes.Results showed that 8strains have capacity of dissolving phosphorus;6 endophytes have capacity of dissolving potassium.Moreover,B.amyloliquefaciens YN-J3 was most potential in producing IAA among the 9 endophytes.The results of the ACC deaminase-producing ability assay showed that all the 9 endophytes had different degrees of ACC deaminase-producing ability.4.The conidia of C.graminicola were treated with B.amyloliquefaciens,the germination rate,germ tube length and appressorium rate significantly decreased.The results of microscope showed that cytoplasm of C.graminicola conidia flew out of cell,indicating cell wall and membrane were broken by B.amyloliquefaciens YN-J3.The germination rate of spores treated by strain YN-J3 decreased to about 50%;the length of germ tube decreased by about 60%;the appressorium did not form or formed a large and light-colored appressorium.The above results indicate that endophyte resources was critical throughout the whole growing season of oat,with the capacity of inducing disease resistance,regulating growth and preventing the invasion of pathogens.B.amyloliquefaciens YN-J3 is an endophytic resource of oat used for leaf spot controlling,with the capacity of inhibiting conidia germination and appressorium formation of C.graminicola.