In this study, two phenol compounds, magnolol and honokiol, were extracted from Magnolia officinalis and identified by LC-MS, ¹H- and ¹³C-NMR. The magnolol and honokiol were shown to be effective against seven pathogenic fungi, including Alternaria alternata (Fr.) Keissl, Penicillium expansum (Link) Thom, Alternaria dauci f.sp. solani, Fusarium moniliforme J. Sheld, Fusarium oxysporum Schltdl., Valsa mali Miyabe & G. Yamada, and Rhizoctonia solani J.G. Kühn, with growth inhibition of more than 57%. We also investigated the mechanisms underlying the potential antifungal activity of magnolol and honokiol. The results showed that they inhibited the growth of A. alternata in a dose-dependent manner. Moreover, magnolol and honokiol treatment resulted in distorted mycelia and increased the cell membrane permeability of A. alternata, as determined by conductivity measurements. These results suggest that magnolol and honokiol are potential antifungal agents for application against plant fungal diseases.

The coumarin compound of osthole was extracted from Cnidium monnieri and identified by LC-MS and ¹H- and ¹³C-NMR. Osthole was tested for anti-virus activity against tobacco mosaic virus (TMV) using the half-leaf method. The results showed that stronger antiviral activity on TMV infection appeared in Nicotiana glutinosa than that of eugenol and ningnanmycin, with inhibitory, protective, and curative effects of 72.57%, 70.26%, and 61.97%, respectively. Through observation of the TMV particles, we found that osthole could directly affect the viral particles. Correspondingly, the level of coat protein detected by Western blot was significantly reduced when the concentrations of osthole increased in tested plants compared to that of the control. These results suggest that osthole has anti-TMV activity and may be used as a biological reagent to control the plant virus in the half-leaf method.

Sugarcane mosaic virus (SCMV) is responsible for large-scale economic losses in the global production of sugarcane, maize, sorghum, and some other graminaceous species. To understand the evolutionary mechanism of SCMV populations, this virus was studied in Shanxi, China. A total of 86 maize leaf samples (41 samples in 2012 and 45 samples in 2013) were collected from 4 regions of Shanxi. Double-antibody sandwich (DAS)-ELISA and RT-PCR showed 59 samples (30 samples in 2012 and 29 samples in 2013) to be positive for SCMV, from which 10 new isolates of SCMV were isolated and sequenced. The complete genomes of these isolates are 9610 nt long, including the 5′ and 3′ non-coding regions, and encode a 3063-amino acid polyprotein. Phylogenetic analyses revealed that 24 SCMV isolates could be divided on the basis of the whole genome into 2 divergent evolutionary groups, which were associated with the host species. Among the populations, 15 potential recombination events were identified. The selection pressure on the genes of these SCMV isolates was also calculated. The results confirmed that all the genes were under negative selection. Negative selection and recombination appear to be important evolutionary factors shaping the genetic structure of these SCMV isolates. SCMV is distributed widely in China and exists as numerous strains with distinct genetic diversity. Our findings will provide a foundation for evaluating the epidemiological characteristics of SCMV in China and will be useful in designing long-term, sustainable management strategies for SCMV.

Blue mold caused by Penicillium expansum is one of the most common apple diseases, and it is becoming a serious threat in apple production. The strain Bacillus amyloliquefaciens Ba168 showed high levels of antimicrobial activity in our previous study. To analyze the antimicrobial protein of Ba168, a high-resolution LC-MS/MS proteomic analysis was performed. A total of 1155 proteins were identified from 5233 unique peptides. A total of 16 potential antimicrobial-activity-related proteins were identified; 10 of these proteins have direct antimicrobial effects, while 6 of these proteins are associated with the formation of antimicrobial substances. Then, an antifungal protein of Ba168 was isolated and purified by the sequential chromatography of DEAE Bio-sep FF anion exchange and Sephadex G-75. The single protein, named BP8-2, showed antifungal activity towards Penicillium expansum. The peptide mass fingerprinting of the protein band of BP8-2 had a high similarity with the amino acid sequences of flagellin protein. The results showed that BP8-2 significantly inhibited the growth of P. expansum and slowed the spread of apple blue mold. The results indicated that flagellin is one of the important antimicrobial substances from Ba168.