Plant Preservative Mixture
Endophytic contaminants are a common problem for in vitro propagation of woody plants and have important economic implications for the conservation of plant genetic resources and commercial micropropagation. In this study, first, microbial contamination that appeared around the base of in vitro-grown apple shoots was identified as Bacillus megaterium. Then, the plant preservative mixture (PPM™) was used as a bactericidal agent in plant tissue culture. Its efficacy was tested to eradicate endophytic B. megaterium in an apple in vitro cultures. In vitro contaminated shoots were grown in tissue culture medium supplemented with 0.2% v/v PPM™ for 12 weeks and then transferred to medium without PPM™ and grown for 24 weeks. This study demonstrated that Plant Preservative Mixture PPM is an effective agent to control the growth of B. megaterium. Our results highlight the species-specific response of apple shoots to PPM. PPMTM was effective in the control of endogenous microbial contamination of ‘Golden Delicious’, ‘Landsberger Renette’, ‘Suislepper’ and ‘Aport krovavo-krasnyi’ apple varieties; meanwhile, in ‘KG 7’ and ‘Gold Rush’, all plants grown in the absence of PPMTM were still contaminated with bacteria, even though they were pretreated for 12 weeks in medium supplemented with PPMTM. Therefore, these results suggest the need for further testing of PPMTM prolonged incubation in these cultivars that had outbreaks of bacterial contamination.
Keywords: Bacillus megaterium; malus; PPM™; biocide; microbial contamination; plant tissue culture.