Effect of Asiatic mangrove plant (Rhizophora mucronata) extract on the growth and virulence of Vibrio harveyi causing bioluminescence disease in Penaeus monodon larviculture

Aim of study: Vibrio harveyi bacteria are affecting shrimps during grow-out practices. The application of chemicals to control V. harveyi has resulted in antibiotic-resistance among bacteria. An extract of the leaves of Rhizophora mucronata was tested to control the growth and virulences of V. harveyi. Area of study: This study was conducted in the Crustacean Culture Division of ICAR-CIBA, Chennai city, Tamil Nadu State, India. Material and methods: R. mucronata plants were collected from the Pitchavaram area, and the leaves contents extracted. The resultant extract was prepared and tested against the growth of V. harveyi and its virulence factors. The various functional compounds of R. mucronata were screened and volatile compounds were analyzed. Main results: When R. mucronata extract was treated against V harveyi (350 mu g/mL) an inhibitory zone of 14 +/- 0.1 mm was observed. At 300 mu g/mL, the extract was found to be active in decreasing the luciferase to a maximum of 76 counts per second in 30 days and a similar level of bioluminescence was reduced in 15 days. During, shrimp larviculture a reduction in the cumulative percent of mortality 15.70% (p<0.033) was observed when treated with the extract of R. mucronata. Research highlights: When extract (200 mu g/mL) of R. mucronata was tested against V. harveyi during Penaeus monodon larviculture, the V. harveyi counts decreased (p<0.049). Volatile compounds viz, tetramethyl-6,7,8,8a-tetrahydro-5H-naphthalene-1-one (38.63%), squalene (31.19%), alpha-amyrin, (7.07%) and beta-amyrin (8.75%) were detected. It would be desirable to use crude extracts of R. mucronata during shrimp culture to control V. harveyi.

Automated summary

The study showed that the extract of R. mucronata had inhibitory effects on the growth and virulence of Vibrio harveyi, reducing mortality rates in shrimp larvae culture. The presence of volatile compounds like tetramethyl-6,7,8,8a-tetrahydro-5H-naphthalene-1-one and squalene in the extract may contribute to its effectiveness in controlling V. harveyi populations.