Robert Wieners and Shui-zhang Fei
Objective
The use of perennial ryegrass has seen significant increases in recent decades, largely due to its improved genetic color, texture, density and environmental stress tolerance. The fast establishment rate, excellent seedling vigor, good wear tolerance and the ability of perennial ryegrass to compete with Poa annua makes it a good choice for use on golf course fairways and athletic fields in Iowa. However, most of the elite perennial ryegrass cultivars do not have adequate winter hardiness to survive severe winters in the northern USA, including Iowa. The goal of this research was to develop new perennial ryegrass germplasm with improved cold tolerance for better persistence in northern climates. The specific objectives of this project were to: 1. screen a USDA perennial ryegrass collection for stress tolerance, and 2. make crosses between improved varieties and wild materials possessing desirable traits and select superior individual plants within the progeny. By utilizing the diversity present in USDA collections, unique germplasm may be created for utilization in turfgrass breeding programs.
Research progress
Field research
One hundred and five accessions of perennial ryegrass collected primarily from temperate regions worldwide and two improved cultivars of 'Accent' and 'Caddieshack' were planted at the ISU Horticulture Research Farm in 2001. Each accession was sown in a 4ft by 4ft plot with three replicated blocks. In the following spring (2002), cold hardiness was assessed by visually evaluating the stand persistence. Although the 2001 winter was considered mild in Ames, some accessions were winter-killed. Sixty-seven out of 105 wild accessions survived and appeared to possess adequate cold tolerance for further investigation. The 67 accessions were scored based on color, texture, and density and then compared to the cultivars Caddieshack and Accent. As a result, plants from 14 accessions with superior traits were selected and taken to the greenhouse for crossing.
Meanwhile, the 67 accessions in the field were allowed to grow to maturity in order to evaluate seed production potential. The plots were then gradually mowed down to a normal turf height of 2.75 inches. After a month of regrowth, opportunistic traits were scored which included rust and leaf spot infestation. Each trait was scored once at the height of infestation and compared to the improved cultivars of Accent and Caddieshack. In addition to disease screening, mowing quality data was obtained. Plots were allowed to grow per typical turf conditions and mowed to approximately 2.75 inches. The amount of leaf tearing was scored and compared to Accent and Caddieshack. From this data, more selections were made. Five additional accessions that exhibited good mowing quality were selected and taken to the greenhouse.
Greenhouse research
Four individual seeds from each accession were also grown in the ISU horticulture greenhouse to screen for seed germination time, shoot development, density and regrowth potential in 2001. In 2002, individual plants were cut several times to score regrowth again. Plants were also screened during the summer of 2002 for heat tolerance. The data obtained from greenhouse experiments resulted in the selection of seven additional accessions for further research.
Each of the original 14 selected accessions were crossed with either Accent or Caddieshack in controlled-pollination. Seeds were then harvested and three progeny of each cross were grown in the greenhouse and transferred to the field for evaluation on cold hardiness, persistence, color, texture, and density.
Conclusions
As a result of the data obtained to present, 26 of the original 105 accessions were chosen for further research. Plants are chosen based upon cold tolerance first, then by three additional criteria. The first group consists of 14 accessions selected based upon color, texture, and density. The second group consists of 5 additional accessions selected based upon mowing quality. The third group consists of another set of accessions selected based upon heat tolerance and regrowth potential. Although most of the accessions that were chosen appeared to have lower quality than Caddieshack and Accent, some accessions had a trait that was comparable. This, however, is not surprising, because most of the accessions, if not all, had never been subjected to human selection, but these accessions may have better cold tolerance that can be incorporated into existing elite perennial ryegrass germplasm.
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ISU Turfgrass:2003 Turfgrass Report | College of Agriculture |
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