Evaluation of Resistance Resources and Analysis of Resistance Mechanism of Maize to Stalk Rot Caused by Fusarium graminearum

Maize stalk rot is one of the most destructive and widely distributed diseases in maize plants worldwide. Research on the performance and resistance mechanism of maize against stem rot is constantly improving. Here, among 120 inbred maize lines infected by Fusarium graminearum using the injection method, 4 lines (3.33%) of them were highly resistant to maize stalk rot, 28 lines (23.33%) were resistant, 57 lines (47.50%) were susceptible, and 31 lines (25.84%) were highly susceptible. The inbred lines 18N10118 and 18N10370 were the most resistant and susceptible with disease indices of 7.5 and 75.6, respectively. Treatment of resistant and susceptible maize inbred seedlings with F. graminearum showed that root hair growth of the susceptible inbred lines was significantly inhibited, and a large number of hyphae attached and adsorbed multiple conidia near the root system. However, the resistant inbred lines were delayed and inconspicuous, with only a few hyphae and spores appearing near the root system. Compared with susceptible inbred lines, resistant maize inbred line seedlings treated with F. graminearum exhibited elevated activities of catalase, phenylalanine ammonia-lyase, polyphenoloxidase, and superoxide dismutase. The authors identified 153 genes related to disease resistance by transcriptome analysis. The mitogen-activated protein kinase (MAPK) signaling pathway and peroxisome pathway mainly regulated the resistance mechanism of maize inbred lines to F. graminearum infection. These two pathways might play an important role in the disease resistance mechanism, and the function of genes in the two pathways must be further studied, which might provide a theoretical basis for further understanding the molecular resistance mechanism of stalk rot and resistance gene mining.