Effects of different culture conditions on conidial formation and germination of Fusarium oxysporum f. sp. medicaginis

To screen suitable culture condition that could effectively promote conidial formation and germination of Fusarium oxysporum f. sp. medicaginis (Fom). Fom strains were cultured in different solid and liquid media PDA, SNA, CMC solid, or liquid (without agar) for various amounts of time. The colony diameter of strains grown on solid media were measured using the cross measurement method. Similarly, microscopy and the hematocrit counting method were used to measure conidial production and proportion in strains cultivated in solid and liquid media and the conidial germination rate in strains cultivated in different liquid media, respectively. Strains cultivated on CMC medium were found to grow the fastest (P < 0.05). Conidial production was highest (P < 0.05) in PDA medium, while that on solid and liquid medium was (1.05 × 10⁶)～(7.63 × 10⁶) conidias·mL⁻¹ and (5.01 × 10⁶)～(9.49 × 10⁶) conidias·mL⁻¹, respectively. Overall, the microconidial proportion was found to be relatively high, while the proportion of macroconidia in CMC medium was the highest (P < 0.05). The same proportion in solid and liquid medium was 0.85%～4.40% and 2.32%～5.63%. The conidial germination rates in PDA and SNA liquid medium were the highest. Furthemore, the longer the culturing period, the higher the germination rate (35.98% and 47.32%, respectively, after 48 h). These results indicated that CMC solid medium was the most conducive to colony formation in Fom, while CMC liquid medium was best in inducing the formation of Fom macroconidia. By contrast, PDA liquid medium favored conidial formation, especially microconidia. Furthermore, SNA liquid media were better for enhancing conidial germination. These results provide a theoretical basis for the prevention and control of alfalfa root rot caused by Fusarium oxysporum.