Assessment of the effectiveness of some antibiotics in limiting the growth of some endogynous bacteria causing infections during in vitro cutting of black pepper plant (Piper nigrum L.)

Determining the optimal type and concentration of antibiotics to be added to the in vitro rooting medium for Vinh Linh black pepper plants is currently an important issue. This will enhance the breeding efficiency and meet the quality and quantity demands for seedlings in the market. The study aimed to determine the effectiveness of three antibiotics Ampicillin, Cefotaxime and Gentamicin on endophytic bacteria isolated from black pepper stem nodes and to determine the appropriate antibiotic concentration to control endophytic bacteria growing duringin vitrocuttings of Vinh Linh black pepper plants. The study included two experiments: the experiment 1 was to determine the effectiveness of antibiotics and antibiotic concentrations against endophytic bacteria isolated from black pepper stem segments and the experiment 2 was to determine the appropriate antibiotics and antibiotic concentrations to prevent endophytic bacteria growing from in vitro black pepper stem segments. Each experiment had 2 factors arranged according to a completely randomized design with 3 repetitions. The results showed that for endophytic bacteria in the stem nodes of Vinh Linh black pepper after being isolated, the antibiotic concentration used was 20 mg/L of all 3 tested antibiotics, which allowed inhibition of colony formation. Meanwhile, the use of Gentamicin antibiotic at a concentration of 40 mg/L gave the best disinfection effect. Under this disinfection condition, the highest survival rate was 89%. The shoot height of Vinh Linh black pepper was highest, reaching 20 mm.