Abstract:
Bacterial contamination is one of the most important problems
both in plant tissue culture research and commercial laboratories. Early
detection of contaminants saves time, effort, and money. Strawberry
runner explants were screened for contaminants during June to August,
1994 and 1995. Most contaminants found were bacterial rather than
fungal. Bacterial contaminants from 22 contaminated genotypes were
isolated, purified, and identified to genus using standard biochemical
tests such as Gram's stain, King's B medium, starch hydrolysis, and
carbon source utilization (Biolog). From those 22 genotypes, 16 different
bacterial strains were isolated. The majority were Gram-negative, motile,
rod-shaped fluorescent pseudomonads. Xanthomonads,
enterobacterium, and other unidentified Gram-negative and Gram-positive
bacteria were also found. Minimal bactericidal concentrations
(MBCs) of single (Timentin, streptomycin sulfate, dihydrostreptomycin,
and gentamicin) and combinations of two and three (Timentin,
streptomycin sulfate, and gentamicin) were tested for inhibition of the
bacterial isolates. Combinations of Timentin, streptomycin sulfate, and
gentamicin killed all bacterial isolates tested. Fragaria virginiana subsp.
glauca (S. Watson) Staudt and F. x ananassa Duch. Cv. Jucunda were
inoculated with Pseudomonas corrugata or Xanthomonas campestris pv.
vesicatoria then treated with a combination of Timentin, streptomycin
sulfate, and gentamicin. F. virginiana subsp. glauca died after
inoculation with either bacteria. Antibiotic treatments were 100%
effective in eliminating P. corrugata from 'Jucunda', but only 23% of the
plants inoculated with X. campestris pv. vesicatoria were freed of the
bacteria.
