Root exudates serve as chemical signaling molecules that regulate rhizosphere interactions and control soil-borne diseases. The interactions between plants and the soil microbiome play dynamic and crucial roles in regulating the resistance of plants to biotic stress. However, the specific roles of many root exudates in plant pathogens remain unclear. The root exudate methyl ferulate, a naturally occurring and relatively non-toxic antifungal agent, has been applied to control postharvest pathogens and preserve foodstuffs and has not been used in plant disease control. This study investigated the role of the root exudate methyl ferulate in controlling tobacco black shank disease. We observed that methyl ferulate was secreted in greater quantities in the tobacco resistant cultivar Gexin 3 following inoculation with P. nicotianae than in the susceptible cultivar Xiaohuangjin 1025. Our findings also revealed that methyl ferulate strongly inhibited P. nicotianae (EC50 = 67.51 µg/mL), effectively controlling tobacco black shank disease by impairing NADH dehydrogenase function (the activity decreased by 50%). Furthermore, methyl ferulate recruited disease-suppressive rhizosphere microbes, such as Bacillus (the relative abundance of these microbes increases from 4.69% to 13.79%), thereby increasing disease resistance. The overexpression of caffeic acid O-methyltransferase NtCOMT10 resulted in increased methyl ferulate secretion (increased to 221.09% compared with that of the wild-type), concomitant improvement in the disease suppression of tobacco black shank disease (disease index decreased from 20% to less than 10%) and enrichment of beneficial microbes. In addition, methyl ferulate exerted antagonistic effects on other phytopathogens, such as B. cinerea, P. aphanidermatum, P. sojae, C. lagenarium and F. oxysporum. Our findings indicated that methyl ferulate, a component of root exudates regulated by NtCOMT10, can inhibit phytopathogens and enrich rhizosphere Bacillus against plant disease. The great dual effect of methyl ferulate on the control of phytopathogens and its low cost enable a novel potential avenue for controlling soil-borne fungal diseases. This study provides ingenious insights into controlling soil-borne diseases through beneficial root exudates.

Wild soybean (Glycine soja Sieb.et Zucc; WS) has been used as a traditional food in China for many years and contains significantly higher levels of isoflavones than cultivated soybean (Glycine max; CS), but the secondary metabolites, including flavonoids and the phenolic composition differences between them, remain unclear. The results showed that WS possessed significantly higher total phenolic and flavonoid content and exhibited better antioxidant and α-glucosidase inhibition activities as well as excellent protective effects against H₂O₂-induced oxidative injury in a human endothelial cell line. Through metabolomic analysis, 642 metabolites were identified, and 238 showed differential expression, with 151 upregulated and 87 downregulated. A total of 79 flavonoid compounds were identified, 42 of which were upregulated in WS. 2′-Hydroxygenistein, garbanzol, protocatechuic aldehyde, ligustilide, and resveratrol were the most discriminated compounds in WS. The metabolic pathway analysis of differential metabolites related to the biosynthesis of flavonoids and phenolic acids were the biosynthesis of phenylpropanoids, flavonoids, isoflavonoids, flavones, and flavonols. This study substantially elucidated differences in the content of flavonoids and biological activities between WS and CS, which is useful information for the effective utilization of these two black soybean species in food processing.

Flos Chrysanthemi indici, an important medicinal and aromatic plant in China, is considered to have many different preservative and pharmacological properties. Considering the capability of essential oils (EOs), the present study is conducted to compare different extraction methods in order to improve yield and biological activities. Hydro-distillation (HD), steam-distillation (SD), solvent-free microwave extraction (SFME), and supercritical fluid extraction (SFE) are employed to prepare EOs from Flos Chrysanthemi indici. A total of 71 compounds are assigned by gas chromatography/mass spectrometry (GC–MS) in comparison with retention indices. These include 32 (HD), 16 (SD), 31 (SFME) and 38 (SFE) compounds. Major constituents of EOs differ according to the extraction methods were heptenol, tricosane, camphor, borneol, and eucalyptol. EOs extracted by SFME exhibit higher antioxidant activity. All EOs show varying degrees of antimicrobial activity, with minimum inhibitory concentration (MIC) ranging from 0.0625 to 0.125 mg/mL and SFME and SFE prove to be efficient extraction methods. EOs alter the hyphal morphology of Alternaria alternata, with visible bumps forming on the mycelium. Overall, these results indicate that the extraction method can significantly influence the composition and biological activity of EOs and SFME and SFE are outstanding methods to extract EOs with high yield and antimicrobial activity.