Effect of the Carbon/Nitrogen Relationship on the Macroconidial Characteristics of Fusarium solani f. sp. phaseoli

Abstract

The effects of carbon and nitrogen concentrations or C/N ratio on the macroconidial characteristics of Fusarium solani f. sp phaseoli were studied. The macroconidia were produced on the modified Czapek agar medium containing various concentrations of glucose (C) and NaNO₃ (N). Eleven among the 14 conidial characteristics were affected by C and C/N ratio; high C and high C/N ratio decreased the pathogenicity, conidial length, microbody area, total nitrogen content, alkaline phosphatase and catalase activities. Conversely, they increased the GT₅₀, conidial width, lipid body area, β-1, 3-glucan and total carbon contents. Lipid content was affected only by C/N ratio; high C/N ratio increased the content. Vacuole area and acid phosphatase activity were affected by N; high N decreased the area and the activity. It was revealed that the conidial charactristics are highly correlated with the C^m/Nⁿ ratio, where C and N represent content of carbon and nitrogen, respectively. The exponents, m and n, are appropriately given depending upon the conidial characteristics. It was also established the regression line of the conidial characteristics on the C^m/Nⁿ ratio. Analysis of variance showed that the degree of conidial characteristics at the various C^m/Nⁿ ratios were significantly different (P=0.05). It is suggested that the conidial characteristics are significantly influenced by the C^m/Nⁿ ratio in the medium.