| | Plants for coastal restoration are typically started in greenhouses and grown in pots before they’re manually transplanted to wetlands areas. Broadening the genetic makeup of these plants can help sustain diversity in the wild. (Photo by Prasanta K. Subudhi) |
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Prasanta K. Subudhi, Niranjan Baisakh, Stephen A. Harrison, Michael D. Materne and Herry S. Utomo
The development of native plant materials with greater usefulness and enhanced performance in coastal wetland environments is of crucial importance to Louisiana’s efforts to arrest coastal erosion and wetlands habitat loss. The key to enhanced productivity and longevity of Louisiana’s coastal marshes lies in planting quality plant materials with adequate genetic diversity.
Genetic diversity indicates the presence of a variety of plant species in a particular ecosystem. Genetic diversity also involves intraspecific diversity – that is, genetic differences among the individuals of a particular species or variation at the level of individual genes. For a particular plant species, it is important to know whether individual plants are genetically similar or diverse within a population and across locations. Differences in certain traits can be indicators of genetic diversity, but the ultimate control of such heritable differences rests with its assemblage of genes or the genetic makeup. It may be easy to see the differences among different plant species, but it can be difficult to discern differences among individuals within a particular plant species. Researchers use DNA fingerprinting techniques to detect the genetic differences among the individuals.
In a coastal restoration context, diversity of plant species is as important as genetic diversity within a plant species. Smooth cordgrass (Spartina alterniflora) is the most important native plant species of the coastal marshes of Louisiana. In addition, several other plant species such as black mangrove (Avicennia germinans), marshhay cordgrass (Spartina patens), salt grass (Distichlis spicata), big cordgrass (Spartina cynosuroides), California bulrush (Schoenoplectus californicus), seashore paspalum (Paspalum vaginatum), bitter panicum (Panicum amarum), sea oats (Uniola paniculata) and several woody plant species occupy different niches in marsh environments depending on salinity, elevation and other factors.
In newly created or eroded marshes, coastal restoration managers should choose a number of plant species adapted to a particular marsh environment. Increasing the number of diverse genotypes within a particular plant species will enable the vegetation to survive stressors in the long term and establish genetically diverse populations similar to that of native populations in a nondisturbed environment.
Currently, there is little diversity among wetland plant varieties released for wetland restoration activities. For example, in the case of smooth cordgrass, Vermilion is the only released material, and Pelican is the sole black mangrove selection released by the Natural Resources Conservation Service. This lack of quantity and diversity of released plant materials for coastal restoration and reclamation project dictates the urgent need for the development of improved wetland plant materials.
The more genetic diversity a population contains, the greater are its chances to adapt and survive in dynamic marsh environments. Genetic diversity provides a sort of insurance against complete destruction of plant populations in the event of natural disaster. In extreme cases, low genetic diversity may lead to complete elimination of some plant species resulting in loss of overall biological diversity. In the summer of 2000, a “brown marsh event” was noticed in a large expanse of Louisiana marshes. All S. alterniflora vegetation was destroyed while the black mangrove population stayed green and intact. This clearly indicates that plant diversity is immensely beneficial for the overall health of the coastal ecosystem. Using a single variety of smooth cordgrass, such as Vermilion, over large restoration plantings leads to genetic vulnerability.
The best way to increase genetic diversity is to develop and release a suite of improved plant materials for use in coastal restoration plantings, while ensuring that the individuals perform well and have different origins and genetic backgrounds. LSU AgCenter scientists are actively engaged in conducting the research that will help increase genetic diversity among plants suitable for coastal restoration and wetland reclamation projects.
At present, our focus is on the improvement of three plant species – smooth cordgrass, sea oats and California bulrush. A number of smooth cordgrass selections with improved vigor, tillering, spreading habit, rust resistance and seed set have been identified. California bulrush clones with improved salt tolerance are under development, and sea oats field trials are being conducted to identify sea oats lines adaptable to Louisiana environments.
Prasanta K. Subudhi, Assistant Professor; Niranjan Baisakh, Postdoctoral Researcher; Stephen A. Harrison, Professor; Michael D. Materne, Instructor, School of Plant, Environmental & Soil Sciences, LSU AgCenter, Baton Rouge, La.; and Herry S. Utomo, Assistant Professor, Rice Research Station, Crowley, La.
(This article was published in the spring 2007 issue of Louisiana Agriculture.) |