A class of second order approximations, called the weighted and shifted Grünwald difference (WSGD) operators, are proposed for Riemann-Liouville fractional derivatives, with their effective applications to numerically solving space fractional diffusion equations in one and two dimensions. The stability and convergence of our difference schemes for space fractional diffusion equations with constant coefficients in one and two dimensions are theoretically established. Several numerical examples are implemented to test the efficiency of the numerical schemes and confirm the convergence order, and the numerical results for variable coefficients problem are also presented.

Based on the weighted and shifted Grünwald difference (WSGD) operators [24], we further construct the compact finite difference discretizations for the fractional operators. Then the discretization schemes are used to approximate the one and two dimensional space fractional diffusion equations. The detailed numerical stability and error analysis are theoretically performed. We theoretically prove and numerically verify that the provided numerical schemes have the convergent orders 3 in space and 2 in time.

BACKGROUND: The resistance of traditional chemical fungicides to plant pathogenic fungi and the threats to the safety of humans and the environment highlight an urgent need to find safe and efficient alternatives to chemical fungicides. Owing to the wide spectrum of antifungal activities, low persistence and nontoxicity to mammals and aquatic life, essential oils have considerable potential as low-risk pesticides. In this study, the essential oil and the main components of Angelica sinensis (Oliv.) Diels (Danggui) were extracted, analyzed by GC-MS, and evaluated for their antifungal activities against six plant pathogenic fungi.RESULTS: 3-butylidenephthalide (3-BPH) showed the best antifungal activity against Fusarium graminearum with an EC 50 value of 14.35 ∼g mL −1 . The antifungal mechanistic studies revealed that 3-BPH induced the generation of endogenous ROS to cause lipid peroxidation of the cell membrane and inhibited the biosynthesis of ergosterol, thereby causing the cell membrane damaged to exert its fungicidal activity. Significantly, 3-BPH could reduce deoxynivalenol production compared to the control.CONCLUSION: This study demonstrated the potent fungicidal activity of natural phthalide compound 3-BPH and highlighted its potential as an alternative agent to control F. graminearum.

In this work, a series of derivatives with disulfide bonds containing pyridine, pyrimidine, thiophene, thiazole, benzothiazole, and quinoline were designed and synthesized based on the various biological activities of allicin disulfide bond functional groups. The antimicrobial activities of the target compounds were determined, and the structure–activity relationships were discussed. Among them, compound S8 demonstrated the most potent antifungal activity in vitro against Monilinia fructicola (M. fructicola), with an EC50 value of 5.92 μg/mL. Furthermore, an in vivo bioassay revealed that compound S8 exhibited equivalent curative and higher protective effects as the positive drug thiophanate methyl at a concentration of 200 μg/mL. The preliminary mechanism experiments showed that compound S8 could inhibit the growth of M. fructicola’ s hyphae in a time- and concentration-dependent manner, and compound S8 could induce the shrinkage of hyphae, disrupt the integrity of the plasma membrane, and cause the damage and leakage of cell contents. More than that, compound S5 also demonstrated an excellent antibacterial effect on Xanthomonas oryzae (X. oryzae), with a MIC90 value of 1.56 μg/mL, which was superior to the positive control, thiodiazole copper.

Phytopathogenic fungi infections have become a major threat to reduce crop yields and dampen human health globally. The mycelium growth inhibition method was adopted to evaluate the antifungal activity of commercially available natural and natural‐like phenols, bioassay results showed that most phenolic compounds exhibited excellent fungicidal activity against Fusarium graminearum, Rhizoctonia solani, Botrytis cinerea, Fusarium oxysporum f. sp. Vasinfectum, Sclerotinia sclerotiorum, and Magnaporthe oryzae. Particularly, compound Z‐5 exhibited an excellent inhibition rate of 100.00 % at 100 μg/mL and EC50 value of 3.20 μg/mL against Fusarium graminearum. In addition, compound Z‐5 displayed the best efficacy and superior fungicidal activity compared to azoxystrobin (EC50=9.78 μg/mL) based on mycelial growth and spore germination. Significantly, compound Z‐5 at 200 μg/mL reduced 4‐deoxynivalenol production by over 98 % compared to the control, through down‐regulation of the gene expression of Tri5 and Tri6. Preliminary mechanism studies revealed that compound Z‐5 might exert its fungicidal activity by inducing accumulation of reactive oxygen species and lipid peroxidation, and causing cell membrane destruction and DNA synthesis interference. This study demonstrated the potent fungicidal activity of the natural‐like phenolic compound Z‐5 and highlighted its potential as an alternative agent to control F. graminearum.