Study On The Stress Response Of Resistant And Susceptible Maize Varieties To Fusarium Graminearum At Seedling Stage

Maize stem-based rot has became one of the main diseases in maize production in China due to its high incidence and serious damage.At present,breeding resistant varieties is the most effective method to prevent and control maize stem-based rot.Clarification the physiological and biochemical index,morphological and histological structures,and pathogen infection dosage of resistant and susceptible maize seedlings under the pathogen stress are the basis to study the disease resistant varieties.Therefore,in this thesis the above mentioned contents were studied systematically in order to clarify the different stress responses between resistant and susceptible maize seedlings to Fusarium graminearum,which provides theoretical support to further clarification of disease resistance differences of maize varieties to the stem-based rot.The results were as follows:1.The POD activities,MDA and soluble sugar contents of the resistant and susceptible maize varieties at two-leaf,three-leaf,and six-leaf stages under the 0 h,6 h,12 h,24 h,36 h and 48 h stress of Fusarium graminearum were tested respectively by colorimetry,thiobarbituric acid and anthrone colorimetry.The results showed that,the POD activities,MDA and soluble sugar contents in resistant and susceptible varieties appeared an ascending trend during 0 ~ 48 h stress of Fusarium graminearum;the POD activities and soluble sugar contents of resistant varieties were higher than those of susceptible varieties,while the MDA contents of resistant varieties were lower than those of susceptible varieties;the POD activities,MDA and soluble sugar contents in the root of resistant and susceptible maize were slightly higher than those in stems and leaves.2.The plant height,stem thickness,and root morphology of the resistant and susceptible maize varieties inoculated during the sowing period were measured at the two-leaf,three-leaf,and six-leaf stages by tape measure,vernier caliper,and digital scanner.The results showed that the inhibition rates of Fusarium graminearum to maize plant height and stem thickness at two-leaf and three-leaf stages were lower than those of resistant and susceptible maize varieties at six-leaf stage,and the inhibition rate to plant height and stem thickness at six-leaf stage in resistant maize varieties was significantly lower than that of susceptible varieties;In the root morphology,the root of resistant and susceptible varieties were influenced at the two-leaf stage,the root of resistant varieties were more longer,thicker,and numerous in root tips than the increments of various indexes on the roots of susceptible varieties;inhibition rates of Fusarium graminearum to the root surface area,volume and average thickness of the susceptible varieties at the three-leaf and six-leaf stages were higher than those of the resistant varieties,and the increments of the total root length,number of root tips and branch numbers of the susceptible maize seedlings were smaller at the three-leaf stage.3.The histological structure of resistant and susceptible maize varieties inoculated during the sowing period were observed by the paraffin sections and scanning electron microscopy.The results showed that,the thickness of epidermal cell wall,epidermal cell,endothelial cell wall,pericylindrical cell wall,duct cell wall of the radicle,node root and mesocotyl of the resistant varieties at the three-leaf and six-leaf stages were thicker than those of the susceptible varieties in the paraffin section,there is no significant difference in vessel diameter,number of vessels,and the ratio of root diameter to central sheath diameter between resistant and susceptible maize varieties;based on the scanning electron microscopy,it was observed that more hyphae in the surface of the radicle of susceptible varieties than that of resistant varieties,and the damage of radicle were more serious than that of resistant varieties.4.The Fusarium graminearum infection dosage in the resistant and susceptible maize varieties inoculated at the sowing period were detected by RT-q PCR technology at the two-leaf stage.The results showed that there were obvious differences in the pathogen infection dosage in resistant and susceptible maize varieties at two-leaf stage,and the content of Fusarium graminearum in the susceptible varieties was significantly higher than those of resistant varieties.