Novel alternative to antibiotics in shrimp hatchery: effects of the essential oil of Cinnamosma fragrans on survival and bacterial concentration of Penaeus monodon larvae.

AIMS: The activity of two essential oils (EOs) of Cinnamosma fragrans, an endemic plant to Madagascar (B8: linalool-type and B143: 1,8-cineole-type), against bacterial isolates from a shrimp hatchery of Penaeus monodon and their effects on the survival and bacterial concentration of larvae were determined. METHODS AND RESULTS: Minimum inhibitory concentrations were determined using a broth dilution technique. The bacterial concentrations of both larvae and water tank were assessed on Marine agar and Thiosulfate Citrate Bile Sucrose agar. The assays took place in OSO Farming's shrimp hatchery in Madagascar. EOs were directly added to the water tank. Regarding the survival, the assays in larval culture (four replicates each of B8, B143, E and control) showed that B8 oil had a similar effect (P > 0.05) as the antibiotic (Erythromycin) and was more active than B143 (P < 0.05). A negative correlation was observed between the bacterial concentration and the survival of larvae for all assays. CONCLUSION: Both C. fragrans essential oils, as antibiotic, exhibited significantly higher survival rates and lower bacterial concentrations of the larvae than the control (oil and antibiotic free). SIGNIFICANCE AND IMPACTS OF THE STUDY: The potential of C. fragrans essential oil to control the bacterial load in in vivo conditions, thereby enhancing survival rate of P. monodon larvae, makes it a relevant option for developing a novel alternative to antibiotics in shrimp hatchery culture.

In vitro propagation of the gum arabic tree (Acacia Senegal (L.) Willd.) 1. Developing a rapid method for producing plants.

The method described herein permitted production of three to four micropropagules of Acacia Senegal from one uninodal explant. The explants were taken from plants produced either in a sterile environment or during four years in a greenhouse. Zeatin or 6-benzylaminopurine (BAP) were mixed, at different concentrations, with Murashige and Skoog's medium (MS) of which the amount of macroelements was divided in half (MS mod.). At a concentration of 5.0×10(-5) M, zeatin produced a better multiplication rate after 60 d for the two types of plant stock than did BAP. A two stage process was necessary to obtain a rooting rate of the small cuttings close to 100%. The first stage, called induction, consisted of leaving the cuttings for 6 to 12 d on a Jordan's medium (JN) of which the amount of macroelements was reduced by half (JN mod.) and in which NAA at a concentration of 5.0×10(-5) M was added. The second stage, called root extension, required that the small cuttings be planted on this second hormone-free medium. Roots appeared after a few days. Acclimatization in a greenhouse occured with a survival rate of close to 100% when the rooted in vitro plants were transplanted to pots containing a mixture of vermiculite and top soil (1∶1; v/v).