In vitro Conidial Germination and Mycelial Growth of Fusarium oxysporum f. sp. fragariae Coordinated by Hydrogen Peroxideand Nitric Oxide-signalling

Yu Jin Do¹ Do Hyeon Kim¹ Myung Sung Jo¹ Dong Gi Kang¹ Sang Woo Lee¹ Jin-Won Kim² Jeum Kyu Hong^1,*

¹Department of Horticultural Science, Gyeongnam National University of Science and Technology (GNTech), 33 Dongjin-ro, Jinju 52725, Korea
²Department of Environmental Horticulture, The University of Seoul, Seoul 02504, Korea

Abstract

Chemicals related to hydrogen peroxide (H₂O₂) and nitric oxide (NO) generations were exogenously applied to Fusarium oxysporum f. sp. fragariae (Fof) causing Fusarium wilt disease in strawberry plants, and regulations of In vitro conidial germination and mycelial growth of the fungus by the chemical treatments were evaluated. H₂O₂ drastically reduced the conidial germination of Fof in a dose-dependent manner, and treatment with 3-amino-1,2,4-triazole (3-AT) catalase inhibitor also led to dose-dependent inhibition of conidial germination but relatively moderately. Gradual decreases in mycelial growth of Fof were found by high concentrations of H₂O₂, whilst exogenous 3-AT slightly increased the mycelial growth. Increasing sodium nitroprusside (SNP) NO donor, NG-nitro-l-arginine methyl ester (L-NAME) NO synthase (NOS)-inhibitor and tungstate nitrate reductase (NR) inhibitor led to dose-dependent reductions in conidial germination of Fof in quite different levels. SNP conversely increased the mycelial growth but increasing L-NAME moderately decreased the mycelial growth. Tungstate strongly enhanced mycelial growth. Differentially regulated In vitro mycelial growths of Fof were demonstrated by SNP, L-NAME and tungstate with or without H₂O₂ supplement. Superoxide anion production was also regulated during the mycelial growth of Fof by nitric oxide. These results show that H₂O₂ and NO-associated enzymes can be suggested as fungal growth regulators of Fof as well as eco-friendly disease-managing agents in strawberry production fields.

Figures & Tables

Regulation of conidial germination of f. sp. by hydrogen peroxide (HO). (A) Germinated conidia of f. sp. isolate SFW-10 on glass slides after treatment with 20 mM of ROS-related chemicals HO and 3-amino-1,2,4-triazole (3-AT) were observed under a light microscope. (Scale bars: 25 μm). (B) Relative conidial germination(%) regulated by the chemical treatments was shown as a percentage of germinated conidia treated with different doses (0, 0.5, 1, 2, 5, 10 and 20 mM) of HO and 3-AT compared to control. Error bars represent standard errors of means of five independent experimental replications. Means followed by the same letter are not significantly different at 5% level by a least significant difference test. The same letter above the bars represented no significant difference between treatments.