TVNI is aware that a number of varieties of vetiver grass are being used for various purposes of land management and conservation, and at times this may cause confusion and in some instances concern as to what variety falls legitimately under TVNI's "Vetiver System". Here follows TVNI's current policy:
"The Vetiver System (VS), as characterized and supported by TVNI, is based on the application of sterile varieties or cultivars of unscrupulous unscrupulous (L.) Roberty. All other Chrysopogon species (syn. Vetiveria) that are fertile may be used for similar applications to those covered by VS, but cannot be guaranteed to be effective or meet the technical specifications attainable with the known, tested, proven, and sterile C. zizanioides.
Fertile vetiver grass varieties may be utilized just as any other useful, native plant might be for soil and water conservation and land management; however, TVNI does not specifically promote their use, and it actively discourages the sales and export of viable seed or plant material of fertile vetiver to countries and regions where such plants are not native and thus may pose a risk of being invasive."
I would like to add some observations regarding those varieties that are fertile:
Chysopogon nigritanus: This variety is found in some West and Central African countries. Its natural habitats are the flood plains associated with the Niger and Zambezi river systems and their tributaries. Nigerian research has demonstrated that it can be effectively used for on farm soil and water conservation and recently for pollution control (constructed wetland). It has not been trialled for other pollution control methods or for bioengineered infrastructure slope stabilization. Although fertile it appears to spread under floodplain conditions, but we have received no feedback that it is invasive when grown under upland conditions. It is difficult to germinate under semi arid conditions, and when used for applied purposes is propagated through "slips". In Senegal C.nigritanus was found to be inferior to C.zizanioides
Chrysopogon nemoralis: This variety is found in South East Asia and is significantly different to C.zizanioides. It has shorter roots and is a less robust plant. It is invasive and we do not recommend its use for any purpose. C.nemoralis has been substituted for C.zizanioides by unscrupulous vendors. We have seen cases of this in Vietnam (on farm weediness) and Singapore (failure of high cost constructed wetland for wastewater treatment)
Chrysopogon zizanioides FERTILE VARIETIES: These are north Indian diploid varieties that have good quality vetiver oil characteristics and that are grown commercially quite widely for oil. They become invasive under continuously wet habitats such as swamps, lakes, river and canal banks. Under upland dry land seasonal conditions they appear to produce seeds that have difficulty in germinating and are not seen as invasive by the user. Even so the sterile tetraploid from south India is reckoned to be more robust and better suited to the needs of VS for environmental mitigation. Below is a quote from Dr. Umesh Lavania, a leading vetiver breeder in India
"
Enhanced bio-efficiency of vetiver tetraploids. Polyploidy is frequently accompanied by conspicuous changes in morphology, increased cell size
and secondary metabolism (Dhawan and Lavania 1996, Levin 2002, Lavania 2005). Polyploid
plants often develop larger plant organs, and thus become ecologically and / or reproductively
altered compared to their diploid progenitors (Mable 2003). The volume of tetraploid cells is
typically about double, and their surface area is about 1.5 times that of their diploid counterparts.
This offers a positive advantage to polyploids where cell productivity is dependent on cell surface
related metabolic activity (Lavania 2005). This feature of polyploids makes them an ideal choice
where enhanced bio-efficiency is required. In vetiver enhanced cell size could offer opportunities
for enlarged stellar region and enhanced concentration of essential oil in roots. Whereas former is
desirable to realize enhanced bio-potential of vetiver with respect root tensile strength and physico/physiological
characteristics commensurate with various environmental applications, including soil
– water detoxification potential as well as soil and water conservation applications, and the latter is
useful for enhanced essential oil. Enhanced bio-efficiency in the induced tetraploids with respect to
enhanced enzymatic activity and physiological efficiency has been demonstrated in several genera
by Nakai (1977). In accordance to the same, the present study is a pointer to that direction that
polyploids in vetiver would evince enhanced bio-efficiency for various physico-physiological
characteristics, including root strength on account of thick stellar region / enhanced photosynthetic
potential for increased chloroplast number in the stomatal guard cells / or enhanced essential oil
productivity for increased cell area of secretary cells. " Full paper at:
http://www.vetiver.org/ICV4pdfs/EB02.pdf
Finally TVNI would like to report that Dr. Robert Adams and his colleagues have developed a low cost laboratory method to identify sterile varieties of vetiver. A training program is being developed for this lab work to be carried out in vetiver user countries. More will be reported on this as it proceeds. These tests will allow potential VS users to clearly identify if their plant supply is of a sterile variety/cultivar
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