GENETIC VARIABILITY ASSESSMENT OF Sonneratia apetala (BUCH. -HAM.) IN THE SUNDARBANS OF BANGLADESH

Abstract

Sundarbans is the single largest tract of natural mangrove forest in the world, which is situated in the south western coast of Bangladesh. This forest defends the south-western coastal region of the country from natural calamities, like cyclones, flood, tidal surges, tsunami etc. Sundarbans is the natural habitat for many mangrove plants. Sonneratia apetala exists in the low saline zone (LS), medium saline zone (MS) and in the high saline zone (HS) as a pioneer tree species of the Sundarbans. Genetic variability of S. apetala in these three saline zones were examined through the adoption of RAPD-PCR molecular marker. The expected heterozygosity of S. apetala in MS and HS (0.75±0.05 and 0.76±0.06, respectively) was greater than that of LS (0.60±0.13). Again, the average gene diversity over loci of this species in the MS and HS (0.59±0.37 and 0.62±0.38, respectively) was greater than that of LS (0.51±0.32). The greater heterozygosity and genetic diversity of S. apetala establishing in the MS and HS are the causes of its higher salt adaptability than that of growing in the LS in the Sundarbans. Due to higher genetic diversity and salt adaptability, S. apetala could persist in the increasing salinities in the Sundarbans. Moreover, S. apetala seedlings derived from the MS and HS zones of the Sundarbans can be planted in the high saline substrates in the coastal regions of Bangladesh, hence got added advantages for the coastal afforestation programs of Bangladesh.