Bacterial contamination in Ilex dumosa (aquifoliaceae) cultures: antibiotic treatment.

LUNA C,; COLLAVINO M.; SANSBERRO P.; MROGINSKI L.

Faro, Portugal

Simposio; 3rd International Symposium on Acclimatization and Establishment of micropropagated Plants.; 2007

ISHS

More than 500 species of Ilex are recognized occurring in tropical  and temperate regions of the words. Approximately 220 species are native to South America and one of these, I.paraguariensis is economically the most important specie because of the value of its leaves for making the stimulatory beverage named “mate”. Lately, “yerba señorita” (I. dumosa) have received the most attention from plant breeders because, besides of the quality of its leaves for making “mate” with less caffeine than the ones from I.paraguariensis, the plants are resistant to some pests. Because of its allogamy, micropropagation  would be of great value for the multiplication of selected clones. However, bacterial (Gram negative) contamination was observed in I.dumosa nodal segments-cultures in our laboratory. With the objective  of solve this problem, 13 treatment with 4 antibiotic were tested: Streptomycin(200 mg.ml-1), Chloramphenicol (50 mg.ml-1), Cefotaxime (0.25, 0.50 and 1 mg.ml-1)  and combinations between Ampicilline (200 mg.ml-1) + Chloramphenicol (50 mg.ml-1), Streptomycin(200 mg.ml-1) + Cefotaxime (0.50 mg.ml-1) ,  Cefotaxime (0.25, 0.50 and 1 mg.ml -1) + Ampicilline (200 mg.ml-1) or Chloramphenicol (50 mg.ml-1).Nodal segments of  I.dumosa were cultured in Murashige and Skoog (1962) medium, quarter strength  (1/4 MS), with 1,5% sucrose and 20μM BAP in a RITAÒ immersion temporal systems (with a frequency of 1 min. each 4 hr )under 27 ± 2 ºC with lighting (cool white fluorescent light) at 116 μmol m -2 and 14   hr photoperiod. After 30 days culture  various antibiotics controlled the proliferation of bacteria. The most suitable treatment was 0.50 mg.ml -1Cefotaxime which permitted 100% of establishment with 100% of explants with shoots with  8 cm in average. Rooting of regenerated shoots produced plants that were successfully transferred in pots.