Survival of Curtobacterium flaccumfaciens pv. flaccumfaciens from soybean and common bean in soil

Abstract

Survival niches for phytopathogenic bacteria are important for disease management. We study the survival of Curtobacterium flaccumfaciens pv. flaccumfaciens (Cff), the causal agent of bacterial wilt in common bean and bacterial tan spot in soybean, in the soil. While Cff strains from common bean already have several studies, the ecology of soybean strains needs more information. We used the strain Feij.2628A from common bean, and CffR1, Cff2R, and Cff4R from soybean. The soils were infested with bacterial suspension (107 CFU.mL−1) from each of the strains. For experiments under laboratory conditions, they were incubated in BOD incubator (biochemical oxygen demand) at 20 °C. Under natural field conditions, pots were maintained in the field without supplementary irrigation. The survival of Cff strains was evaluated every seven days until they were not detected. The identity of the bacterium was confirmed in all treatments by PCR. Under laboratory conditions, the survival period of Feij.2628A ranged from 140 to 154 days, and between 77 to 119 days for the soybean strains. Feij.2628A and Cff1R survived for a maximum of 91 days in soil with higher clay content, under natural field conditions. Cff survival was negatively influenced by high temperatures, low soil moisture, and precipitation in some treatments. These results demonstrated the potential survival of Cff strains from common bean and soybean in the soil, being potential inoculum sources for subsequent cultivations of these crops. Fallow periods ranging from three to four months may reduce the amount of inoculum in soils under these conditions.