In vitro effect of salinity and pH on Fusarium sp., the causal agent of sweet-potato root rot

Fusarium root rot in a common pathogen of sweet potato, with a wide range of host plants. In the current study six new isolates of Fusarium sp., collected from infected sweet potato plants, along with a reference strain of Fusarium oxysporum, had their growth behavior studied in various pH and saline conditions. In vitro studies showed that salinity higher than 6% NaCl in the PDA substrate significantly reduces the fungal growth. At 12% NaCl, four of seven strains revealed complete mycelia inhibition. However, for the other two isolates, and for the reference strain, 12% salinity only reduced the growth with 77.4%. Regarding the fungal growth at different pH values, it was noticed that tested fusaria were not perturbed at up to 8.5 alkalinity. However, at a pH of 4.5, the growth rate was reduced, although the growth differences were diminished during prolonged incubation time. Considering the in vitro results, saline water should be tested as preventive immersion treatment on the sweet potato sprouts, before their planting, in order to reduce the incidence of Fusarium infection.