Broomcorn millet (Panicum miliaceum L.) affected by smut (caused by the pathogen Sporisorium destruens) has reduced production yields and quality. Determining the tolerance of broomcorn millet varieties is essential for smut control. This study focuses on the differences in the phenotypes, physiological characteristics, and transcriptomes of resistant and susceptible broomcorn millet varieties under Sporisorium destruens stress. In diseased broomcorn millet, the plant height and stem diameter were reduced, while the number of nodes increased. After infection, the activities of superoxide dismutase and peroxidase decreased, and malondialdehyde and relative chlorophyll content (SPAD) decreased. Transcriptome analysis showed 514 and 5452 differentially expressed genes (DEGs) in the resistant and susceptible varieties, respectively. The Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis of DEGs showed that pathways related to plant disease resistance, such as phenylpropanoid biosynthesis, plant–pathogen interaction, and plant hormone signal transduction, were significantly enriched. In addition, the transcriptome changes of cluster leaves and normal leaves in diseased broomcorn millet were analysed. Gene ontology and KEGG enrichment analyses indicated that photosynthesis played an important role in both varieties. These findings lay a foundation for future research on the molecular mechanism of the interaction between broomcorn millet and Sporisorium destruens.

Land alkalization is an abiotic stress that affects global sustainable agricultural development and the balance of natural ecosystems. In this study, two broomcorn millet cultivars, T289 (alkaline-tolerant) and S223 (alkaline-sensitive), were selected to investigate the response of broomcorn millet to alkaline stress and the role of brassinolide (BR) in alkaline tolerance. Phenotypes, physiologies, and transcriptomes of T289 and S223 plants under only alkaline stress (AS) and alkaline stress with BR (AB) were compared. The results showed that alkaline stress inhibited growth, promoted the accumulation of soluble sugars and malondialdehyde, enhanced electrolyte leakage, and destroyed the integrity of broomcorn millet stomata. In contrast, BR lessened the negative effects of alkaline stress on plants. Transcriptome sequencing analysis showed that relative to control groups (CK, nutrient solution), in AS groups, 21,113 and 12,151 differentially expressed genes (DEGs) were identified in S223 and T289, respectively. Gene Ontology (GO) and the Kyoto Encyclopedia of Genes and Genomes (KEGG) revealed various terms and pathways related to metabolism. Compared to S223, alkaline stress strongly activated the brassinosteroid biosynthesis pathway in T289. Conversely, ARF, TF, and TCH4, associated with cell growth and elongation, were inhibited by alkaline stress in S223. Moreover, alkaline stress induced the activation of the mitogen-activated protein kinase (MAPK) pathway, the abscisic acid signaling pathway that initiates stomatal closure, as well as the starch and sucrose metabolism. The EG and BGL genes, which are associated with cellulose degradation, were notably activated. BR enhanced alkaline tolerance, thereby alleviating the transcriptional responses of the two cultivars. Cultivar T289 is better in alkalized regions. Taken together, these results reveal how broomcorn millet responds to alkaline stress and BR mitigates alkaline stress, thus promoting agriculture in alkalized regions.