Identification Of Head Smut Resistance Germplasm And Initial Localization Of Disease-resistant Genes In Sorghum

Sorghum bicolor belongs to the genus sorghum of the family gramines,Monocotyledon.Sorghum bicolor is an annual herb with a waxy epidermal cover,typical C4 plant specialized photosynthetic organs,high photosynthetic efficiency function and high yield potential,and has temperature tolerance,drought resistance,flood resistance and salt and alkali resistance.In China is also one of the important dryland crops,is the world’s fifth ranking food crops.However,head smut is one of the most important diseases in sorghum production.It is difficult to control and pollute the environment by chemical control,so it is impossible to ensure the high yield and high quality of sorghum.Because the sorghum silk smut has the characteristics of infection at seedling stage,pregnancy stage and heading stage,it is impossible to identify whether it is infected with silk smut by physiological characteristics or appearance characteristics at early stage.Therefore,it is very important to establish the identification technology of disease resistance breeding.On the basis of determining the optimum conditions for artificial culture of UUT scitaminea,it is of great significance to further understand the infection of different tissues of sorghum susceptible to pathogens for the study of the pathogenic mechanism of sorghum.At the same time,two resistant DNA pools were constructed for high-throughput sequencing to screen the candidate genes of head smut resistance in sorghum.Homology analysis and co-expression gene analysis of the candidate genes were carried out to lay a foundation for the cloning and functional analysis of the resistance genes.The main results are as follows:1.Different training conditions have significant effects on the germination of spores in different areas.The proper temperature of winter spores of Guiyang’s physiological strain of 1 is 30 ℃,that of Shenyang’s physiological strain of 2 is 30 ℃,and that of Yuci 3 is 24-30 ℃.For p H,the best spore germination of Guiyang’s physiological strain of 1,Shenyang’s physiological strain of 2 and Yuci’s physiological strain of 3is 7-9.Excessive acid will inhibit spore germination,but the inhibition effect of superacid is stronger than that of superalkali.Both glucose and sucrose solutions promote spore germination and were highest when both glucose and sucrose concentrations were 0.5%.Spore germination was treated with ammonium sulfate,potassium nitrate and ammonium nitrate.The best nitrogen source concentrations required for ammonium nitrate and potassium nitrate are similar to 0.5%.However,the concentration of ammonium nitrate is slightly different in three different places: 1% ammonium nitrate is most suitable for the germination of Yuci’s physiological strain of 3 physiological spores,and 0.5% concentration of ammonium nitrate is suitable for Guiyang’s physiological strain of 1 physiological species and Shenyang’s physiological strain of2 physiological species thick wall spore germination.2.There were differences in tissue and cell expression between resistant and susceptible sorghum cultivars inoculated with Panicella nigrifolia.Through microscopic observation on the tissue parts of sorghum,it was found that Ustilago scitaminea could germinate not only in leaves,but also in young tissues such as stems and roots of seedlings.Mycelia and spores could be clearly observed in the roots,stems and leaves of infected sorghum plants,and obvious lesions were observed in the stems.Spore also existed in roots,stems and leaves of uninfected sorghum plants,and hyphae could be clearly observed.The leaf and root tissues of resistant sorghum were intact.No spores and hyphae were found,but some spores existed in the stem.No spores and hyphae were observed in the leaves of resistant sorghum,but a few spores and hyphae were found in the stem and root of resistant sorghum.3.Two mixed pools of extreme resistance DNA were constructed,and the resistance gene of sorghum silk black panicle was preliminarily mapped within 31.05 Mb of chromosome 4.Four important candidate genes were screened by BSA method,which might be related to the anti-head smut function.Sobic.004G102100,Sobic.004G116300,Sobic.004G126050 and Sobic.004G126100.Homologous genes of these 4 candidate genes were found in Arabidopsis database.Through gene functional annotation of homologous genes and co-expressed genes in Arabidopsis thaliana,it was found that they had disease resistance related functions,and most of them were NBS-LRR resistant genes,which more accurately indicated that the four candidate genes screened in this study were candidate genes with disease resistance function.