RAPD profiling and isozyme analysis of New Zealand Hydrilla verticillata

Hydrilla verticillata is an invasive submerged weed, which has been introdu ced and become established in a variety of freshwater habitats around the w orld. It was first recorded in New Zealand in 1963, and today occurs in fou r lakes in the Hawke's Bay region. Isozyme analyses (six enzyme systems; MD H, PGM, PGD, GPI, AAT and IDH) were carried out on these populations to det ermine the level and pattern of genetic diversity in New Zealand H, vertici llata. Australian and USA monoecious and dioecious H. verticillata samples were also analysed for the same six enzyme systems. Four isozymes (MDH, PGM , GPI and AAT) were polymorphic between country-samples. Isozyme banding pa tter-Its of New Zealand H. verticillata populations were compared with thos e of H. verticillata from other countries, both by examining published data as well as by direct analysis, to determine the likely source of H. vertic illata in New Zealand. Random amplified polymorphic DNA (RAPD) reaction car ried out on the same sample set using 14 random primers indicated that ther e was a single dominant genotype present in all four New Zealand H. vertici llata populations. USA and Australian H. verticillata samples contained mor e than one genotype. Both analyses indicated that the New Zealand H. vertic illata plants were more similar to those from Australia than to either of t he USA samples. The study also indicated that New Zealand H. verticillata w as probably the result of a single introduction, the most likely source bei ng Australia, and that reproduction is solely by vegetative means. (C)2000 Elsevier Science B.V. All rights reserved.