Evaluation And Identification Of Maize Ear Rot Resistance

As one of the most important crops in China,maize is both a food crop and a feed crop,which is widely used.Maize ear rot is a major disease that causes corn production reduction and poor grain quality.Spike grain infected with ear rot will also produce mycotoxins,careless consumption will cause more serious harm,and ear rot will not only cause maize loss in the field,but also improper storage will spread the bacteria.There are many kinds of pathogenic bacteria of maize spike rot,with sickle spore accounting for the most proportion.Breeding and popularizing excellent varieties with strong disease resistance is an effective measure to reduce the loss caused by maize ear rot.In this study,we identified and evaluated spike rot resistance in 980 maize inbred lines vaccinated with F.gramicum in the field in 2021.On this basis,8 high resistance and high sense inbred lines were selected for spike rot pathogen inoculation,determine and analyze leaf physiological indexes on different sampling days,and then analyze the physiological response performance of maize inbred lines with different disease resistance to spike rot resistance.This study results are as follows:1.Identification of spike rot resistance in the field.There is extensive genetic diversity in the disease resistance of 980 test materials.From the perspective of pedigree relationship,the genetic background contains the same or similar paternal,maternal inbred lines,which has a relatively consistent resistance to spike rot.Most inbred lines containing Demia 1 and Delta 2 showed high resistance or ear rot resistance,which may be related to the high resistance to stem rot in Demia 1 and Delta 2 with high resistance to stem rot.Inbred lines containing method 3-4 and Liangyu 88 are susceptible,which may be related to the resistance of stem rot in Liangyu 88.Of the 980 maize inbred lines,283 were identified as high resistance,28.8%,311 showed strong disease resistance（R）,31.7%,240 were general disease resistance（MR）,24.4%;124 were susceptible to infection（S）,12.6%;13 showed high sensitivity（HS）,1.3%.2.Analysis of the physiological mechanism of indoor ear rot resistance.The enzymatic activity of PAL after pathogen induction is positively correlated with the induced disease resistance of varieties,and the metabolism is rapidly activated,which initiates the rapid establishment of defense systems such as phytoalexin and lignin,thus showing the induced disease resistance characteristics of the host.After SOD was activated by pathogens,the enzyme activity of each variety showed an upward trend,and the increase rate was related to the variety resistance.The stronger the variety resistance,the greater the increase of the enzyme activity.The results showed that the PAL and SOD activity were regular,and the artificially inoculated plants were higher than the control,showing a positive correlation with the resistance of maize spike rot.It can be used as an index for rapidly detecting the resistance of the variety to ear rot disease.CAT rapidly decreases in enzyme activity after being threatened by pathogens,and because CAT has high homology with salicylic acid receptor proteins,they together participate in the conduction of disease resistance signals.After virus infection,the salicylic acid content increases and the bound SABP increased accordingly,thus inhibiting the CAT activity.However,the difference in resistance enzymes in different varieties is not large,indicating that CAT plays a role in maize against pathogens,but it has little to do with the disease resistance of varieties.