Turfs for many challenges
1 Jan, 2004 By: Crystal Rose-Fricker, Dr. Melodee L. Fraser Landscape ManagementIndustry's demands for turf to solve key management issues drive turfgrass breeders to keep coming up with "new and improved" grasses
When it's time to finish a landscape construction project by installing the turf, do you think about the research and development that went into that bag of seed or pallet of sod? Have you ever considered that a plant breeder had specific management challenges in mind when he or she was developing that turfgrass? Turfgrass breeders work on many projects with many species, but the goal is always the same: to minimize the management inputs that will have to be put into the turf.
Tremendous progress has been made in breeding grasses for turf. Some characteristics have been relatively easy to improve and the benefits are easy to see. Others are more difficult.
New advances
Darker green varieties require fewer nitrogen fertilizer applications to look attractive. Lower-growing varieties reduce mowing frequency. Higher density varieties provide less room for weed encroachment. Varieties that contain fungal endophytes have improved insect resistance. Newer advances in turfgrass breeding are producing exciting results: varieties with improved heat tolerance, disease resistance, salt tolerance and herbicide tolerance are examples. How are these varieties developed? Greenhouse salt baths test turfgrasses' response to high salinity levels. |
Some of the turfgrass breeding projects we conduct at Pure Seed Testing, Inc. are described in the following paragraphs.
Pure Seed Testing, Inc. operates two research farms where turfgrass breeding projects are jointly conducted - one in Oregon and the other in North Carolina. The warm, humid climate in North Carolina allows for selection of cool-season turfgrasses with improved heat tolerance to summer diseases. Simultaneously, the Oregon environment allows for evaluation of turf quality and improvement of seed yield and seed production disease resistance. An example of the success of this cooperative breeding program is a project dedicated to improving brown patch resistance in tall fescue.
The primary disease that attacks tall fescue in its major use area is brown patch. Caused by an aggressive fungal pathogen, Rhizoctonia solani, brown patch is most problematic in warm, humid weather. While brown patch can be controlled with fungicides, it's often used in lower maintenance areas where preventive fungicides aren't routinely applied. The best control for this disease, therefore, is genetic resistance in the tall fescue host.
At our North Carolina research farm, tall fescue turf trials are planted each fall. During the summer, these trials are managed to encourage brown patch disease development. The trials are evaluated for disease symptoms throughout the summer and plots with little or no visible disease symptoms are identified. Plants are dug from these plots and are planted into spaced-plant nurseries, in Oregon, where they can be evaluated for seed yield potential and seed production diseases like stem rust.
Plants with good disease resistance and yield potential are allowed to interpollinate. Seed is harvested and used to plant turf trials in Oregon again the next fall. The turf plots in North Carolina are managed to encourage brown patch development, and the turf plots in Oregon are rated for overall turf quality.
 Tall fescue undergoes salt screening trials to test its performance against high salinity levels. |
This cycle is repeated until varieties that maintain good brown patch resistance, turf quality and seed yield are identified.
Pass the salt
Salt tolerance is becoming increasingly important in many turfgrass situations. More turf areas are being irrigated from poor quality or effluent water sources. Many sites, such as seaside and roadside turfs, come into direct contact with salt or saltwater. Turfgrass varieties with salt tolerance are valuable for these sites and should help reduce maintenance costs.We've been studying genetic salinity tolerance in several turfgrass species since 1995. In greenhouse salt baths, turfgrasses are subjected to high salinity levels created with a synthetic ocean mix. We have conducted trials with all cool-season turfgrass species and Bermudagrass.
Plants that survive at high salt concentrations are selected from these greenhouse trials and are crossed with one another. Resulting seed is used to establish turf evaluation, seed yield and additional salt screening trials.
We have developed at least three perennial ryegrasses that can survive 17,000 ppm as whole plants in an ocean bath. We have also learned that some varieties can germinate with saline water and others can't. Charger II had an 84% germination rate at 10,000 ppm. "Moonlight" and "North Star" were the top Kentucky bluegrasses out of the Commercial NTEP that tolerated 10,000 ppm for three months. 'Tar Heel II' and "Pure Gold" were the top tall fescues that tolerated 25,000 ppm for two months.
Herbicide tolerance
We've also been working on the development of herbicide tolerant turfgrass varieties for more than a decade. Through conventional breeding techniques, cool-season turfgrass plants have been selected for genetic tolerance to one or more of the following herbicides: diclofop, glufosinate, glyphosate and imazethapyr. Individual plants are sprayed with various rates of herbicide at different stages of the plants' development. Surviving plants are selected and crossed with one another. Seed is subsequently harvested and used to start a second round of selection for herbicide tolerance. This cycle continues for a number of generations until a variety with herbicide tolerance is developed.Once a turfgrass variety has been determined to have valuable improved characteristics, seed of the variety must be increased to make the variety available to the turfgrass management customer. The breeder produces a small amount of breeder seed, which is planted to produce a generation of foundation seed. Foundation seed is planted to produce certified seed.
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