Antifungal Activity and Action Mode of Cuminic Acid from the Seeds of Cuminum cyminum L. against Fusarium oxysporum f. sp. Niveum (FON) Causing Fusarium Wilt on Watermelon

Abstract

In order to develop a novel biofungicide, the antifungal activity and action mode of cuminic acid from the seed of Cuminum cyminum L. against Fusarium oxysporum f. sp. niveum (FON) on watermelon was determined systematically. In this study, the median effective concentration (EC₅₀) value for cuminic acid in inhibiting mycelial growth of FON was 22.53 μg/mL. After treatment with cuminic acid, the mycelial morphology was seriously influenced; cell membrane permeability and glycerol content were increased markedly, but pigment and mycotoxin (mainly fusaric acid) were significantly decreased. Synthesis genes of bikaverin (Bike1, Bike2 and Bike3) and fusaric acid (FUB1, FUB2, FUB3 and FUB4) both were downregulated compared with the control, as confirmed by quantitative RT-PCR. In greenhouse experiments, cuminic acid at all concentrations displayed significant bioactivities against FON. Importantly, significant enhancement of activities of SOD, POD, CAT and decrease of MDA content were observed after in vivo cuminic acid treatment on watermelon leaves. These indicated that cuminic acid not only showed high antifungal activity, but also could enhance the self-defense system of the host plant. Above all, cuminic acid showed the potential as a biofungicide to control FON.

Keywords: biofungicide; disease management; p-isopropylbenzoic acid; watermelon fusarium wilt.

Figure 1

Effect of cuminic acid on mycelia morphology of FON. (d–f) Untreated plates; (a–c) Plates treated with cuminic acid at EC₅₀ value (22.53 μg/mL). Values are means and standard errors.

Figure 2

Mycelial relative conductivity of FON with or without cuminic acid treatment at the concentration of EC₅₀ value (22.53 μg/mL). Values are means and standard errors.

Figure 3

Glycerol content of mycelia of FON with or without cuminic acid treatment at concentrations of EC₃₀ (5.6 μg/mL), EC₅₀ (22.53 μg/mL) and EC₇₀ (91.3 μg/mL). Bars denote the stand error of three experiments. Data represents means of three replicates with standard deviation. Data (means ± SD, n = 3) followed by the same letters in the row show no significant differences (small letters, p < 0.05).

Figure 4

Mycotoxin production (mainly fusaric acid) concentration in FON with cuminic acid treatments at concentrations of EC₃₀ (5.6 μg/mL), EC₅₀ (22.53 μg/mL) and EC₇₀ (91.3 μg/mL) in liquid culture. Bars denote the stand error of three experiments. Data represents means of three replicates with standard deviation. Data (means ± SD, n = 3) followed by the same letters in the row show no significant differences (small letters, p < 0.05).

Figure 5

SOD (a); POD (b) and CAT (c) activities and MDA activity (d) of the watermelon leaves treated with cuminic acid at 0, 1000, 2000 and 3000 μg/mL, respectively. Data represents means of three replications with standard deviation. Data (means ± SD, n = 3) followed by the same letters in the row show no significant differences (small letters, p < 0.05).

Figure 6

Gene expression level of synthesis of fusaric acid (FUB1, FUB2, FUB3 and FUB4) and bikaverin (Bike1, Bike2 and Bike3), and components of a velvet-like complex (Lae1 and Vel1) relative to without treatment cuminic acid. Values are the means ± standard error (SE) of three repeated experiments.