Evaluation Of Germplasm Resources For Resistance To Stalk Rot In Maize And Analysis Of Kinship

Maize is an important crop with many functions,such as food,feed ect.Stalk rot is a serious soil-borne disease,which has become one of the most threatening diseases in maize production with the wide application of mechanical harvesting and direct grain harvesting.In this study three inoculation methods were used.Eight hundred maize inbred lines with different genetic backgrounds were selected and evaluated for stalk rot resistance.The following results were obtained:1.The comparison of three inoculation methods,including stem-based injection,seedling inoculation and soil-buried root injury,showed that soil-buried root injury was greatly affected by the environment,and the stability of inoculation effect was poor.Besides,the preparation of inoculum and inoculation process were complicated and the work was heavy,and the identification period was long.The operation of traditional stem-based injection inoculation is complicated,and it is necessary to split the stem at the inoculation site to observe the spread of pathogens during the later disease investigation,which has a large workload and a long identification cycle.Compared with the above two methods,inoculation method at seedling stage is simple to operate and more convenient to identify.2.The identification results of stem rot resistance showed that there was extensive genetic diversity in the resistance of the tested materials.In terms of pedigree relationship,there were the same or similar inbred lines of the male parent and the female parent in the genetic background,and the resistance to stem rot was relatively consistent.Among the 800 inbred lines tested,360 were highly resistant,accounting for45% of the total.174 inbred lines were resistant to stem rot,accounting for 21.75% of the total.There were 193 inbred lines susceptible to stem rot,accounting for 24.125% of the total.73 inbred lines were highly susceptible to stem rot,accounting for 9.125% of the total.Among the 360 highly resistant inbred lines,157 were from group A(SS),89 were from group B(NSS),and 114 were from group C(heterozygous and Eukaryotic).Among the 73 highly susceptible inbred lines,47 were from group A(SS),10 were from group B(NSS),and 16 were from group C(heterozygous and European hard seed).The proportion of resistant materials in group B(NSS)was 82%,and that of susceptible materials in group A(SS)was 37.6%.Therefore,inbred lines with group B lineage tend to be more resistant to stem rot.3.Analysis of related physiological traits of resistant and susceptible inbred lines showed that POD,SOD activity and other physiological indexes of resistant inbred lines decreased 7 or 14 days after inoculation,and increased 21 and 28 days after inoculation,indicating that the enzyme activity in plants increased gradually with the invasion of pathogenic bacteria.The physiological indexes of healthy plants without inoculation were stable.The physiological indexes of susceptible inbred lines were generally lower than those of resistant inbred lines due to invasion of pathogenic bacteria.In conclusion,inoculation at seedling stage is more suitable for identification and evaluation of maize stem rot resistance.Inbred lines with group B lineage tend to be more resistant to stem rot.Inbred lines with different resistance had different physiological response to pathogen infection.