ABSTRACT
Soybean genotypes used as food are susceptible to Xanthomonas axonopodis pv. glycines (Xag). This bacterium is transmitted by seeds and is difficult to control, justifying the need of conducting seed health tests before commercialization or sowing. Culture media for bacterium detection in seeds should be practical, rapid and sensitive. The aim of this study was to detect the presence of Xag in soybean seeds on semi-selective culture medium. On the semi-selective culture medium MXG with and without antibiotics and on the routine culture medium 523, the serial diluted (10-1 to 10-7) bacterial suspension (109 CFU mL-1, OD550 = 0.5) of the isolate UFU C35 from Xag was cultivated on Petri dishes with 3 replicates for each dilution. After 4 days, the number of colony forming units per mL (CFU mL-1) was quantified. Statistical analysis was performed according to Kruskal-Wallis test. For detection of the bacterium in soybean seeds, five genotypes were evaluated: 0012.UB010/11-P, 0012.UB1501/11-P, 0012.UB037/11-P, 0012.UB003/11-P and NT12 Paraná. In an Erlenmeyer, 100 g of seeds were added of 200 mL of 0.85% saline solution and incubated for 18 hours in a refrigerator. Seed extracts underwent serial dilution (10-1 to 10-2) and plating on the culture media MXG with antibiotics and 523, using 6 replicates for each dilution, followed by incubation at 28 °C. After 4 days, the number of CFU g-1 seeds was quantified. The means of treatments were compared according to Tukey’s test at 5% probability. The semi-selective medium MXG with and without antibiotics did not inhibit the development of Xag, and the medium MXG with antibiotics was effective to detect the bacterium in soybean seeds of all evaluated genotypes, which can be used in routine analyses.
Keywords
Glycine max; bacterial pustule; soybean for human food
