Plant-to-seed transmission of Curtobacterium flaccumfaciens pv. flaccumfaciens on soybean.
Curtobacterium flaccumfaciens pv. flaccumfaciens (Cff) causes bacterial tan spot on soybeans (Glycine max), which was detected in Brazilian crops in 2012. The objective of this study was to determine the Cff transmission rate from plant to seeds in soybean cultivars with different levels of resistance to bacterial tan spot. For this, two assays were conducted under greenhouse and laboratory conditions. Inoculation in soybean plants was performed by the stem puncture method in the first assay and the toothpick method in the second assay. The Cff transmission to seed was checked by plating the suspensions extracted from seeds of the inoculated plants on semi-selective medium. Molecular identification of Cff amongst the obtained isolates was performed by PCR. The susceptible cultivars, BRS 284 and NS 5858 RR, showed zero to 1% Cff seed transmission, while the moderately resistant cultivar, BRS 388RR, showed 0% seed transmission. We concluded that Cff can be transmitted to soybean seeds of susceptible cultivars at low rates.