LAUSR

Abstract In the present study, sugar beet inoculated with Pectobacterium betavasculorum and two different initial population densities of Heterdera schachtii were investigated in three different infection time. Four-leaf stage seedlings were inoculated with initial population densities of 1500 and 2500 second stage juveniles of H. schachtii per pot and at seven days before, at the same time and at seven days after nematode inoculation, the soil of each pot was infested with a suspension of 10 mL/kg soil of P. betavasculorum (108 CFU/mL) and compared with non-inoculated control. The results showed that inoculation of P. betavasculorum prior to 1500 and 2500 J2s of H. schachtii per pot, respectively, decreased 13.8% and 17.5% of shoot length, 19.04% and 34.3% of shoot dry weight and 14.3% and 13.6% of the shoot fresh weight compared to the nematode inoculated + bacterium non-inoculated plants and increased 34.3% and 36.1% of cyst number in soil, 30.1% and 45.9% of female and cyst number in the root system and caused 32.7% and 30.4% of decrease in reproduction factor compared with bacterium non-inoculated plants. Inoculation of P. betavasculorum seven days prior to H. schachtii caused a greater damage compared to simultaneous inoculation of H. schachtii and P. betavasculorum and inoculation of H. schachtii seven days prior to P. betavasculorum.