Growth kinetic model of Fusarium oxysporum under different pH

Fusarium wilt disease in agricultural crops caused by Fusarium oxysporum facultative fungi has always been difficult to control. In this paper, the effects of different pH on the growth characteristics of six F. oxysporum strains isolated from different host plants were studied by constructing a kinetic model with growth characteristics of F. oxysporum inoculated on potato sucrose (PS) agar mediums with different pH levels. The tested six F. oxysporum strains could grow in PS liquid medium with pH 3~9. pH changes of PS liquid medium with different stains was similar, closing to 6~7 after 14 days cultivation. This colony was divided into 4 categories (hyhae, stick-slip, hyhae and stick-slip, and hyhae with powdery types) in the range of pH 3~9. The hyhae and culture medium colors of the strains were different. F. oxysporum growth rate in different pH media was determined at 25 ℃, which was later used to build the kinetic growth model. Growth rate was affected by medium pH. The optimal growth (with maximum average colony diameter of 45~49 mm) was attained in the range of pH 6~8, followed by pH 4, 5 and 9, with colony diameter significantly smaller (17~21 mm) at pH 3, 10 and 11. Colony morphology and color were affected by media pH after 14 days cultivation. Differences existed among stain sporification at different pH, with the highest average sporification (223.8~273.3)×104 cfu·mL^-1 in the range of pH 4~8. Sporification was highest at pH 6.38 (natural pH) and was lowest at pH 11. Strain colony growth and sporification at different pH were best depicted by quadratic equation.