Junwei Yang

Northern corn leaf blight (NCLB) is a leaf disease caused by Setosphaeria turcica that infects maize at multiple growth stages and severely impairs photosynthesis and grain yield. Breeding for resistance to NCLB would be an effective strategy to mitigate the damage caused by this disease. Mapping of resistance genes provides an opportunity to understand the resistance mechanisms and to utilize the information in developing an introgression breeding strategy. The resistance of 421 maize inbred lines with extensive genetic variation to NCLB was evaluated over three consecutive years in Xinzhou, Shanxi. The proportions of maize lines classified as highly resistant, resistant, moderately resistant, susceptible, and highly susceptible were 1.06, 7.16, 20.16, 37.13, and 34.48%, respectively. A total of 39,676 high-quality SNP markers were employed for genome-wide association study (GWAS). In the early and late stages, 85 SNPs associated with NCLB resistance were identified, of which 11 stable SNPs were detected across the two environments. Through comparative transcriptome analysis, 4,758 and 3,779 differentially expressed genes (DEGs) were identified in the resistant inbred line Jing724 and the susceptible inbred line PH4CV after infection with S. turcica, respectively. GO and KEGG analyses indicated that more DEGs were enriched in plant defense pathways in the resistant line. Furthermore, two candidate genes were identified by integrating GWAS and transcriptome analyses. These findings could provide a foundation for cloning resistance genes and breeding resistant varieties.

Ear rot caused by the Fusarium species has led to a decline in maize yield and kernel quality worldwide. The changes in the population structure of pathogens and the widespread planting of susceptible maize varieties have exacerbated the occurrence and harm of ear rot in China. Therefore, it is very important to establish the species composition of Fusarium and evaluate the resistance of the main cultivated hybrids. In this study, 366 single conidial isolates of Fusarium spp. were obtained from three provinces of Northeast China. F. verticillioides, F. subglutinans, F. proliferatum, F. oxysporum, and F. graminearum species complex (FGSC) were identified, with F. verticillioides being the most prevalent with a frequency of 44.0%. Based on the TEF-1α gene sequences analysis, the FGSC populations consisted of two independent species: F. boothii and F. graminearum, which account for 23.8% and 5.7% of the total isolates, respectively. Additionally, the resistance to ear rot by 97 maize hybrids commonly planted in Northeast China was evaluated by inoculation with F. verticillioides during 2021 and 2022. The results showed that the disease parameters of different hybrids varied significantly (p < 0.05). Approximately half of the hybrids had damage rates ranging from 0 to 15%, and 79.4% of the hybrids had a severity rating of less than 5.5. In total, 49 (50.5%) hybrids were rated as moderately resistant, which was the dominant resistance category, and 71 hybrids (73.2%) were identified as moderately to highly resistant to ear rot. Current research confirms that Fusarium ear rot in maize is mainly caused by F. verticillioides in Northeast China, and many hybrids are resistant to the disease. This study will guide growers to scientifically deploy resistant commercial hybrids to control ear rot.