Effects Of Ustilago Maydis Infection On Tissue Cells And Photosynthetic Characteristics Of Maize Leaves At Seeding Stage

Maize smut is one of the main diseases threatening maize production safety in China.Long-term studies on maize disease resistance showed that it was the most economical and effective control measures to collect maize disease resistance resources,excavate resistant genes and breed resistant varieties by molecular breeding.In the early stage,the research group used the inbred line Q319 with high resistance to smut as the donor and the inbred line Ye478 with high susceptibility to smut as the recurrent parent to construct the chromosome fragment replacement line R445,which could significantly improve smut resistance.This test by R445 and recurrent parent Ye478 as material,artificial inoculation tumor black powder injection,clear tumor black powder mellea against feeling material node in different time（0d、4d、8d、12d）seedling leaf tissue cells and the response characteristics of photosynthetic characteristics,for the thorough analytical tumor smut laws and disease resistance molecular breeding to provide theoretical and material basis.The main results are as follows:1.WGA-AF-488/PI staining technique was used to identify the degree of infestation of melomellae on maize resistant material leaves.The results showed that the slow growth of mycelia on leaf surface of R445 was inhibited.The mycelia on the leaf surface of Ye478 grew rapidly and could be rapidly amplified and multiplied to produce a large number of mycelia branches.Scanning electron microscopy（SEM）was used to trace the dynamic process of melomellae melomellae infection on leaves of maize resistant materials.The results showed that the growth of mycelia on leaves of R445 was limited and the proliferation of branches was inhibited,and the penetration of mycelia into epidermal cells was blocked.The mycelium on the leaf surface of Ye478 grows rapidly,and the mycelium branches produce rapidly,and the mycelium can penetrate the epidermal cells smoothly into the cell interior.2.Photosynthetic pigments of maize resistant material leaves were measured to determine the changes of photosynthesis of different materials after infection by M.melomelata.The results showed that the total chlorophyll content,chlorophyll A content and chlorophyll B content of leaves of R445 and Ye478 decreased gradually with the infection of M.melomelata,but the decrease range of R445 was less than that of Ye478.The results indicated that the amount of chlorophyll degradation and damage degree of mesophyll cells of R445 were less than that of Ye478.The sense of corn resistant materials leaf photosynthetic gas exchange parameters determination,specific tumor black powder bacteria infection after assimilation of different material and the change of the accumulation of photosynthetic product,the results showed that the Ye478 leaf net photosynthetic rate（P_N）,transpiration rate（E）,stomatal conductance（gsw）and water use efficiency（WUE）did fall by over R445 nodes in every time,With the prolongation of pathogen infection time,the intercellular CO₂concentration（Ci）of different materials increased slightly.The results showed that the influence of melomellae melomellae infection on assimilation ability and photosynthate production of R445 was less than that of Ye478.The effect on photosynthesis was mainly limited by non-stomatal factors.Chlorophyll fluorescence parameters of leaves of maize resistant materials were measured to determine the difference of damage degree of photosystem caused by different materials after infection by MELanoderma tuberosus.The results showed that:Initial fluorescence（F₀）,maximum fluorescence（F_m）,original light energy conversion efficiency（F_v/F_m）,photochemical quenching coefficient（q P）,actual photochemical quantum yield（△F/F_m’）of photosystemⅡ（PSⅡ）and photosynthetic electron transport efficiency（ETR）of leaves of R445 and Ye478 showed a decreasing trend.The fluorescence parameters of Ye478 decreased more than that of R445,and the non-photochemical quenching coefficient（q N）of different materials showed an upward trend.The results showed that R445 had higher energy absorption,utilization,conversion efficiency and heat dissipation capacity than Ye478.3.Reactive oxygen species（ROS）accumulation in leaves of maize resistant material was determined and stained.The results showed that ROS accumulation in leaves of R445 was less than that of Ye478.