| | Herry Utomo harvests seed heads from bulrush at the LSU AgCenter Rice Research Station in Crowley for further research. (Photo by Bruce Schultz) |
| | | Plantlets grown from callus culture in Petri dishes eventually can be transplanted to produce whole plants for coastal restoration. (Photo by Herry S. Utomo) |
| | | Individual plants developed in the laboratory can be grown in smallspaces and evaluated for natural variability. (Photo by Herry S. Utomo) |
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Herry S. Utomo, Michael D. Materne, Stephen A. Harrison, Prasanta K. Subudhi and Niranjan Baisakh
A large-scale revegetation technique that can restore interior marshes affected by erosion is crucial to successfully reduce of coastal marsh loss in Louisiana. Degradation rates and marsh loss are not uniform in all areas. Accelerated rates of subsidence, canal dredging, a cumulative increase in the area of canals and spoil deposits are major factors contributing to the increase in wetland loss rates. In many cases, marsh losses are highest where saltwater intrudes freshwater marshes and native vegetation is unable to cope. Improved varieties of native marsh plants including vegetatively superior, high seed producing smooth cordgrass (Spartina alterniflora) and salt-tolerant California bulrush or bulwhip (Schoenoplectus californicus) can help stabilize affected areas and rejuvenate degraded marshes by providing resilient, living structures that hold fragile soils and thrive under brackish and saline conditions.
Several key steps are required to develop genetically superior, fertile smooth cordgrass lines. These include establishing foundation plots, DNA fingerprinting identification, evaluating cultural practices and conducting aerial seeding experiments currently funded by the U.S. Department of Agriculture and Louisiana Sea Grant. LSU AgCenter researchers have developed 13 elite lines using various plant sources, including 40 Rice Research Station collections and 126 ecotypes cooperatively collected with the USDA Natural Resources Conservation Service.
These elite lines have been widely tested and have shown superior growth and excellent seed production characteristics as compared to wild types. These seed-producing lines have seed set of 33 percent to 94 percent and germination rates of 53 percent to 90 percent. Wild types have much lower fertility and seed viability. These lines are under preparation for release for commercial production. Small foundation plots for these lines have been maintained at the Rice Station and at the LSU AgCenter’s Central Research Station at Baton Rouge.
Planting, Harvesting
Current planting practices in restoration projects are both labor-intensive and costly. Labor requirements for collecting, cultivation and planting container plants range from $6 to $8 per container and can easily approach $2,700 to $3,500 per acre, depending on planting location. In addition, hand planting across large areas requires site access with equipment and mobility around the site. Using container plants as the only means to restore marshes would leave out a great number of marshes in Louisiana because they simply are inaccessible or too fluid to physically support a ground-based planting operation. In comparison, the seed-based propagation technique will only require a fraction of the cost because with aerial seeding, hundreds of acres can potentially be planted in a day.
Seeds of smooth cordgrass can be obtained by harvesting them from the wild. The amount of seed that can be harvested, however, varies from one year to another depending on seed production and inefficiencies associated with hand harvesting. Because these seeds are gathered from genetically unknown materials, it is difficult to predict germination and performance. Seed production under a managed environment, however, will provide a steady supply of smooth cordgrass seed, and the size of the operation can easily be adjusted to meet the demand. Because genetic materials to produce seed have gone through extensive testing, the performance of the resulting smooth cordgrass population will be more predictable than that of the seeds collected from the wild.
Alternative Crop
Smooth cordgrass could be an alternative agricultural crop in some areas. This plant has the ability to tolerate a wide range of salinities, from sea strength to freshwater. Populations of smooth cordgrass have been cultivated and maintained under freshwater conditions at several research institutions for years and have performed consistently well. Because smooth cordgrass can be cultivated in a broad range of salinity environments, it is reasonable to assume that large-scale commercial seed production is probable and could be an adjunct crop to rice production with little modification to existing equipment or land. In addition, because of increasing salt contamination of inland groundwater, many areas historically used for rice production have been abandoned, thus providing opportunity for smooth cordgrass production as an alternative crop.
California Bulrush
Native to Louisiana, California bulrush is a perennial, deep-water plant species with an extensive network of rhizomes that form dense colonies. California bulrush can provide a natural barrier by dissipating wave energy to provide calmer environments, which enhance the establishment of other vegetation along shorelines. California bulrush can be used to stabilize newly created marshes and terraces and rehabilitate disturbed sites. Its seed and above-ground structure provide favorable habitat for wildlife, including some endangered species. The potential of California bulrush for erosion control is limited by the fact that it is a freshwater marsh plant that can only tolerate salt concentrations of up 6 parts per thousand. Greater salt tolerance in California bulrush will increase its role in preserving and restoring salt marshes.
In cooperation with the Natural Resources Conservation Service’s Plant Materials Program, 48 bulrush ecotypes that demonstrated higher than normal salt tolerances were collected from marshes across Louisiana. These ecotypes were evaluated in replicated field trials at the Rice Station in 2004 and 2005. Nine promising lines with good spreadability, stem density, biomass accumulation and seed production were selected for multi-location trials in 2006 at Cameron, Pointe Aux Chene and Avoca Island. Greenhouse screening to determine the salt tolerance level among these ecotypes was also carried out in the same years. After exposure in a salt concentration of 12 parts per thousand in continuous flooding for six months, eight plant lines were recovered, increased in the greenhouse and included in the replicated multi-location trials together with the original nine lines.
In an attempt to further improve salt-tolerance, parts of actively growing flowers from one of the most tolerant lines were used to produce callus cultures on media containing growth regulators. This produced millions of break-free individual cells. Under appropriate laboratory conditions, these individual cells will be capable of self-regeneration into whole plants. Instead of thousands of acres to grow millions of plants, this approach reduces the task to laboratory-size Petri dishes.
Our cellular selection using millions of cells has yielded 384 lines generally regarded as salt-tolerant. These lines currently are being grown in the greenhouse for further evaluation in the field in coming years. These salt-tolerant mutants are not considered genetically modified and, therefore, will not be subjected to a strict regulation associated with the use of genetically modified organisms. If these plants retain their salt tolerance as they did at the cell level, they will be readily available for use in coastal marsh restoration.
Certification Program
Professionally grown certified seed or plant material is a prerequisite for efficient and successful large-scale revegetation. In addition to being field-inspected, laboratory-tested and approved by professionals, the certified seed label is proof that the seed or plant material has met all of the standards set forth by the regulatory agencies. Establishing a coastal plant certification program would be in the interest of many plant development programs. It would allow interested parties to communicate, exchange information and agree upon quality standards. DNA fingerprinting could be used to identify and maintain genetic purity of cultivated varieties during the certification process.
Herry S. Utomo, Assistant Professor, Rice Research Station, Crowley, La.; Michael D. Materne, Instructor; Stephen A. Harrison, Professor; Prasanta K. Subudhi, Assistant Professor; and Niranjan Baisakh, Postdoctural Researcher, School of Plant, Environmental & Soil Sciences, LSU AgCenter, Baton Rouge, La.
(This article was published in the spring 2007 issue of Louisiana Agriculture.) |