Vetiver in Thailand: General Aspects and Basic Studies - The Vetiver ...

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4Genetic studyIn general, the ecotype and phenotype characterizations were used to identifyvetiver in Thailand. However, the minor nucleotide variations may also triggermorphological, physiological and biological differences. Srifah et al. (2002) haveconducted an experiment for genome analysis of 42 Thai vetiver ecotypes. The resultcould show that both single-strand conformational polymorphism (SSCP) and randomamplified polymorphic DNA (RAPD) analyses for DNA polymorphism are sufficientto distinguish each ecotype of Faek Don and Faek Hom.For karyomorphological study, Kongpraphon et al. (2003) developed acytological technique to display chromosome morphology in cells obtained from theroot tip of 15 Thai vetiver ecotypes. It was found that all studied ecotypes had thesame chromosome number of 2n = 2x = 20. The variation in satellite chromosomes interms of number and morphology was evident in six ecotypes. The total chromosomelength varied from 1.5-8.4 micrometers. The karyotype consisted of metacentric andsubmetacentric chromosomes, all of which were nearly symmetrical. Localization ofthe heterochromatic regions on the chromosome was achieved by modified C-bandand N-band. All the pairs of chromosomes were identified by these banding patterns,along with their length and arm ratios. They can be used as the basis for reproduciblekaryotypes and for detecting chromosomal relationships among ecotypes. Eachecotype showed at least one chromosome with a whole dark band, indicating aconstitutive heterochromatin. The remainder indicated variation patterns from ecotypeto other ecotypes of the some faint and dark bands.To understand the background of vetiver chromosome behavior, Kongpraphonet al. (2005) observed chromosome association in various stages of meiotic celldivision and correlated them with the previous studies. The result showed that themeiotic division in five vetiver ecotypes studied seemed to be normal with only a fewof them showing abnormality. Numerous micronuclei appeared to be related with thenumber of satellite chromosomes. The ecotypes with 1-2 satellite chromosomes hadnumerous micronuclei in meiotic cells while the ecotypes without satellitechromosome appeared to have no micronuclei.Plant development and breeding studyThe information on vetiver development is important for successfulcultivation. Kaveeta et al. (2000) studied shoot apex development, rate of leafprimordial initiation and the rate of leaf appearance on main stem of four vetiverecotypes namely; Surat Thani, Ratchaburi, Sri Lanka and Kamphaeng Phet 1. Theresults revealed that the four ecotypes had similar patterns of apex development, butdiffered substantially in the duration and rate of each development. All four ecotypeshad similar linear relationships in the leaf primordial production and performed anexponential relationship with faster leaf production for the first 150 days; thereafter,the rate would slow down. They produced tillers that fitted to the quadraticrelationship by which slow tillering was observed during the early stage ofdevelopment.
5Tissue culture technique has been used for veitver propagation as it canproduce large quantity of plantlets and it is convenient for transportation for plantingin other places. In order to promote rapid multiplication, the Department of Botanyresearch team successfully developed this technique using lateral or terminal buds ofvetiver with a 70 % survival rate of plantlets. Since 2002, they have propagated anddistributed more than 100,000 vetiver seedlings each year to various governmentaland non-governmental organizations for the promotion of vetiver technology.With tissue culture technique, Na Nakorn et al. (2000) experimented to inducesalt tolerance in nine vetiver ecotypes. From the results, the 50-gray gamma irradiatedcalli of Kamphaeng Phet 1 ecotype exhibited maximum degree of salt tolerance. Thecalli could tolerate up to 4% NaCl, higher than those of without radiation at 3%NaCl. The plantlet regeneration of salt tolerant calli is the next goal of this researchteam.Plant cells resistant to herbicides have been produced by in vitro selection andsuccessfully used in the study of herbicide resistant plant production. Prasertsongkunet al. (2002) performed an experiment to select vetiver cells suspension resistant toglufosinate and investigated the mechanisms of resistance. They could select vetivercells which were 170-fold resistant to glufosinate, compared to the susceptible cells.The glutamine synthetase (GS) activity of the resistant cells was twice as high as thatof the susceptible cells. These results showed that the resistance of the selected vetivercell suspension to glufosinate is mainly due to increasing GS activity and its decreasein sensitivity to the herbicide.Vetiver and soil fertility studySoil fertility, which is an important factor for agricultural productivity, isinfluenced by parent material and inappropriate soil management practices. Manyresearch works on soil fertility improvement by vetiver have been investigated. Theexperiment done by Roongtanakiat et al. (2000) revealed that vetiver mulchingconserved topsoil moisture and increased available-N, available-P and extractable-K.The further experiment showed that one tonne of dry vetiver shoot buried at the depthof 10 cm would yield mineral N, available-K upto 4.4, 2.2 and 20.5 kg while that lefton the soil surface would yield only 0.85, 0.74 and 7.20 kg, respectively (Chairoj andRoongtanakiat, 2004).Vetiver cultivation could improve some chemical and physical properties ofsoil. Tantachasatid (2003) cultivated vetiver in laterite soil, Phon Phisai soil series.After nine months, a certain level of improvement of soil properties such as pH,organic matter, available-P, extractable-K, aggregate stability, bulk density,permeability and available water capacity, could be achieved by cultivation of vetiveras a sole crop and mixed cropping with cover crops.Soil microorganisms associated with vetiver are important for vetiver growthand development especially in infertile soil. They produce nutrient sources and induceplant growth hormones for vetiver. Techapinyawat et al. (2000) reported that VAmycorrhiza inoculated to vetiver significantly increased plant biomass and the nutrientuptake. With isotope tracer technique, Techapinyawat et al. (2002) studied the effectsof 3 species of arbuscular mycorrhizal fungi: Acaulospora scrobiculata, Glomus sp.,Glomus aggregatum in combinations with phosphate fertilizer on P-uptake of vetiver.
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