Yanwen Xiong, Shui-zhang Fei and Reed Barker*
In recent decades, the use of perennial ryegrass has seen significant increases, largely due to its improved genetic color, texture, density, and environmental stress tolerance. The fast establishment rate, excellent seedling vigor, and good wear tolerance make it a good choice for use on golf course fairways and athletic fields. One disadvantage of using perennial ryegrass, however, is that it does not have adequate cold hardiness to survive severe winters in the northern part of USA including Iowa. Therefore, development of improved cultivars or germplasm of perennial ryegrass with enhanced winter hardiness would greatly benefit the turfgrass industry in Iowa as well as in northern USA.
Winter hardiness of perennial ryegrass is a complex trait that is controlled by multiple quantitative genes with each gene having minor phenotypic effects. Because of the environmental effect and the interaction between genes controlling winter hardiness and the environment, it would be difficult to identify these quantitative genes through conventional genetic methods. DNA molecular markers, however, offer a great promise to identifying genes responsible for winter hardiness. There are abundant DNA marker variations that exist in natural plant populations; some of these markers are in the same chromosome as the genes that are responsible for winter hardiness. Often these markers transmit together with the winter hardiness genes into their progenies. Unlike the winter hardiness genes that may be difficult to identify due to the environmental influence, DNA molecular markers are stable and relatively easy to identify. The long-term goal of this project is to efficiently select winter hardy perennial ryegrass germplasm with marker-assisted selection (MAS). The objective of this research is to use molecular biology tools to identify molecular markers that are closely associated with winter hardiness in perennial ryegrass. In addition, molecular markers that are closely associated with other important agronomic traits including rooting, growth habit, etc., will also be investigated.
Research methods
Plant materials A segregating population of 174 genotypes was created by crossing a perennial ryegrass cultivar 'Manhattan' with an annual ryegrass cultivar 'Floregon'. While 'Manhattan' has good winter hardiness, 'Floregon' is very sensitive to winter killing. This population was maintained in our research greenhouse at 20-21ºC and fertilized with Miracle Gro to prevent nutrient deficiency. Irrigation was provided as needed. Four clones of each genotype were planted within each replication in an a lattice design with three replications. The distance between individual clones of a genotype is 30cm, and the distance between each genotype is 60 cm. The distance between rows is 90 cm.
Measurements Component traits of winter hardiness will be measured. These will include traits such as fall growth after the last cutting, LT50 (the temperature at which half of the plants die), visual scores for winter injuries, tiller angles, root morphology including depth, root dry weight, the ratio of root dry weight / shoot dry weight and other chemical components. DNA marker profiles for each genotype have been obtained at Oregon State University.
Data analysis This project was started in the spring of 2003. Single factor analysis of variance will be computed for each marker and trait combination once data for each measurement becomes available. The trait values of all individuals having a marker will be compared with those without this marker by using an F-test. Multiple regression analysis will be performed with data for all markers to identify the best polygenic models for each trait.
*Reed Barker, Research Geneticist, USDA-ARS, Oregon State University, Corvallis, OR
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ISU Turfgrass:2003 Turfgrass Report | College of Agriculture |
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