Histological And Cytological Differences Of Infection By Ustilago Maydis And Identification Of Inbred Lines

Ustilago maydis is one of the main diseases in maize producing areas in China.The most economical and effective measure to control the disease is to improve the resistance of varieties.Inoculation identification and resistance analysis were performed on 204 maize inbred lines by artificial injection.To analyze the histological,cytological and physiological differences of maize seedling resistant to Ustilago maydis is the basis and prerequisite for further understanding of the pathogenesis of Ustilago maydis.In this study,resistant inbred lines Q i319 and susceptible inbred lines Ye478 were used as materials,and using WGA-AF-488 / PI staining and paraffin sections to clearly infect the difference in infection levels between susceptible materials at 0d,2d,4d,8d and 12 d after inoculation with the Ustilago maydis,so as to track the dynamic pathogenesis of the resistant materials.Sem and tem were used to analyze the differences of cellular structure between different time nodes.Using a microplate reader to analyze physiological indicators of susceptible materials at different time points for detection,revealing the physiological changes of susceptible materials in leaf seedlings to the infestation of Ustilago maydis.Clarify the histological,cytological,and physiological differences of corn resistance to Ustilago maydis,and provide important theoretical basis for exploring host defense pathways and screening resistant materials.The main results are as follows:1.Through the artificial inoculation of teliospores,204 maize inbred lines were identified,and it was found that the resistance of different maize germplasm to melanoma powder was different.Most of the Linda red bone,Lancaster,siflaps,BSSS and PA germplasm were susceptible to disease first,while PB maize germplasm with subtropical and tropical consanguineous relationship had relatively good resistance.2.Through the observation of WGA-AF-488/PI staining on the leaves of the resistant materials infected by Ustilago maydis at different time nodes,Ye478 showed rapid expansion and reproduction of mycelia.Qi319 hyphae slow growth.3.Using paraffin section against feeling blade to histological differences.Ye478 bundle sheath cells to divide to form new vascular bundle sheath cells,new bundle sheath cells further divided destroy the wreath structure of vascular bundle sheath cells,mesophyll cells expanded form of bladder,12 d bladder infection for starch sta ining observation found that accumulate large amounts of starch in the bladder.When Q i319 was infected for 8 days,the vascular bundle sheath of Qi319 began to split,and the garland structure remained intact.4.Using Sem to track the dynamic process of U stilago maydis infection resistant materials,it was found that Ye478 mycelium grew rapidly and infected the corn by penetrating cell epidermis and stomata through the generation of attachment cells.The growth of hypha on the surface of Q i319 was inhibited.Wires impede penetration of leaf epidermis5.The ultrastructure of the seedling leaves of the resistant materials at different time nodes was analyzed,found that infected material Ye478 sheath cells and mesophyll cells of chloroplasts gradually expand,the deformation for spindle rounded,stroma lamella and grana lamella by fuzzy clear gradually transformed into a complete fracture,the number of the starch grains increased gradually,finally sheath cells and the organelles of mesophyll cells dissolved gradually disappear,watch less than complete cellular structure.The resistant materials were all Q i319 sheath cells and mesophyll cells.The chloroplast and chloroplast stroma lamella were intact and clear.The number of starch grains in sheath cells decreased sharply at the end of infection,while the number of mitochondria increased gradually.Mesophyll cel s gradually vacuolize mitochondria at the end of infection.6.To analyze the changes of soluble sugar,defensive enzyme and malondialdehyde contents in the leaves of the resistant materials infected by a.mellifera at the seedling stage,the soluble sugar content of Ye478 gradually increased,and reached the maximum at the end of infection.The soluble sugar content of Q i319 increased first and then decreased.The detection and analysis of defensive enzymes showed that the peroxidase(POD)activity of the resistant materials showed an increasing trend,and the POD enzyme activit y of the resistant materials Q i319 was always higher than that of the susceptible materials Ye478.The change of superoxide dismutase(SOD)activity in the resistant material Q i319 was earlier than that in the susceptible material Ye478.The catalase(CAT)activity of the affected materials had a small change compared with that of the control group.The CAT activity of the resistant materials Q i319 continued to increase until it reached the maximum at the end of infection,and the CAT activity of the resistant materials Q i319 was always higher than that of the susceptible materials Ye478.