Screening Of Antagonistic Organism Against Pyricularia Setariae Nishik And The Response Of Foxtail Millet To Ustilago Crameri Koern

Foxtail millet(Setaria italica(L.)Beauv.)is one of the traditional crops in northern China.All kinds of diseases occur because of the expansion of planting areas.Among them,millet blast and millet smut are two common diseases,which occur in many planting areas with varying degrees,and affect the yield and quality of millet seriously.At present,the research about the prevention of millet diseases mainly focuses on the chemical agents and the traditional methods of selecting and breeding resistant varieties.But the both have limitations.We screened the antagonistic strain against Pyricularia setariae Nishik from the rhizosphere soil of foxtail millet,identified it and found its antipathogenic activity.In addition,we explored the physiological and biochemical mechanism and molecular mechanism of the interaction between millet and Ustilago crameri,in order to provide the experimental basis for the biological control of millet diseases and the breeding of resistant varieties.The main results are as follows:1.93 actinomycetes strains were separated from the rhizosphere soil of foxtail millet.One of them named A26 strain showed the strongest antagonistic effect against Pyricularia setariae.Based on morphological,physiological and biochemical characteristics and 16 S rDNA sequence analysis,A26 strain was identified as Streptomyces flavotricini.Furthermore,the cell-free fermentation filtrate of A26 had significant inhibition on growth of Pyricularia setariae Nishik.Inhibitory percentage was increased with increasing the dose of fermentation filtrate of A26 and reached 87.4% when the volume of fermentation filtrateat reached to 50%.It was indicated that A26 strain had potential application in the control of millet blast.2.Two different millet varieties(resistant varieties Jigu 20 and susceptible varieties Changnong 35)were used as experimental materials.The seed mixed Ustilago crameri was planted in fields and pots,and the seed without Ustilago crameri was used as control.The materials were sampled when the field plants grew up to mature stage and the pots plantsgrew up to five leaves.We detected the activities of phenylalnine ammonialyase(PAL),polyphenol oxidase(PPO),chitinase,beta-1,3-glucanase,peroxidase(POD),superoxide dismutase(SOD),and the content of malondialdehyde(MDA),total phenols,flavonoids,lignin in different growth periods,in order to analysis physiological and biochemical mechanism of the interaction between Ustilago crameri and millet.The results showed that the changes of PAL,PPO,POD activity and the content of total phenols had obviously positive correlation with the disease resistance;the activity of SOD and the content of MDA showed significant correlation,that the millet planted in fields and pots could reduce MDA content and alleviate membrane lipid oxidative damage by inducing SOD activity to increase;the activities of chitinase and beta-1,3-glucanase in fields and potted millet had different trends,which may be related to the environment and seedling stage of the plants.3.Resistant varieties Jigu 20 were used as the experimental material.The seed mixed Ustilago crameri was planted in pots,and the seed without Ustilago crameri was served as control.When the millet grew up to five leaves stage,transcriptome analyses were carried out to analysis the response of millet to Ustilago crameri sampling the aerial parts.The results showed that the number of genes in the control group and the treatment group were 23797 and 23421 respectively,and the number of differentially expressed genes was 3653,of which 966 were up-regulated,and 2687 were down-regulated.GO functional analysis showed that there were 2677 differentially expressed genes annotated to 52 GO functional categories,which were mainly divided into three family: molecular function,cell component and biological process.KEGG pathway enrichment analysis showed that there were 2676 differentially expressed genes annotated to 90 pathways.Disease related pathways involved metabolic pathway,biosynthesis of secondary metabolites pathway,plant-pathogen interaction pathway,phenylpropanoid biosynthesis pathway,plant hormone signal transduction pathway,MAPK signaling pathway,flavonoid biosynthesispathway,terpenoid backbone biosynthesis and et al.In addition,the genes4CL?CCR?RPM1?WRKY22?FLS2 and CHIB related to disease resistance were screened and tested by semi-quantitative RT-PCR.It was found that the genes were all up-regulated in treatment group.