Seeds of change
The domestication and improvement of plants and animals was, and continues to be, essential to the progress and prosperity of civilization. Agricultural scientists and practitioners have become much more productive, increasing world food production nearly three-fold since the end of the World War II, using essentially the same amount of arable land. Though farming techniques have improved, much of this increase is due to genetic changes of food crops. As the world's population continues to grow, additional progress is vital.
Modern breeders use relatively sophisticated technology to develop new varieties of plants and animals. However, selective breeding predates modern science by thousands of years. For millennia, people have taken advantage of naturally existing genetic diversity to create specialized types of plants and animals. Witness the great diversity of dogs, horses, wheat, maize and cotton developed through eons of genetic improvement. The wild ancestors of these creatures were far less useful than their modern descendents. The same is true of turfgrasses, even though turf-breeding efforts are a relatively recent thing compared to efforts to improve other plants and animals.
We grow turfgrasses in a wider range of soils, exposures, uses and management regimes than any other crop plant. Like cultivated grasses, wild species occur in practically every kind of habitat, having adapted to these niches over long periods of evolution. Wild grasses have had to survive grazing(from domestic as well as wild herbivores) and nearly every kind of environment and climate. If any group of plants could satisfy the demands we place on turf, it would be the grasses. Thus, nature has been our greatest turfgrass breeder. Even so, of the thousands of species of grasses, only a few dozen have proved successful as turfgrasses.
Modern turf improvement Many people consider Arlington, Va., to be the birthplace of scientific turfgrass breeding. In the years preceding World War II, an exceptionally capable group of researchers was assembled by the U.S. Golf Association's Green Section to improve turfgrass cultivars and management practices. These researchers obtained plant samples from many locations and transplanted them to the Arlington Turf Garden. This was an excellent environment in which to subject turfgrass selections to severe stress and thereby weed out all but the most hardy and pest-resistant types.
The Arlington Turf Garden was eliminated when the U.S. government built the Pentagon on the site. Fortunately, some of the valuable selections were transferred to various U.S. Department of Agriculture facilities and The Pennsylvania State University. These selections eventually led to the release of landmark varieties including 'Merion' Kentucky bluegrass, 'Meyer' zoysiagrass and vegetatively propagated creeping bentgrasses.
The ancestries of most of our major cool-season turfgrasses trace back to species native to the cool, maritime climates of the British Isles and northwestern Europe, as well as to the dry, hot-summer/cool-winter regions of southern Europe. Early immigrants to Eastern North American brought Kentucky bluegrass, fine and tall fescues, ryegrasses and bentgrasses in seed mixes, hay and bedding. Most of these plants were not well-adapted to the hot and humid summers, cold winters, diseases and insect pests of the Mid-Atlantic region, Transition Zone and Midwest states. However, a few were able to survive, persist and even thrive in this new environment. These plants and their offspring provided much of the germplasm used by the people at Arlington, Va., and other early turfgrass breeding programs.
Perennial ryegrass Most American turf-type perennial ryegrasses can be traced to plants selected from old turfs of the United States. An examination of thousands of old lawns, parks, sports fields, cemeteries and golf courses was started in 1962. It showed that, of the trillions of ryegrass seeds used to establish these turfs, only a few plants were able to persist and spread enough to form attractive turfs at least 3 feet in diameter. Researchers collected the most attractive plants and evaluated them in mowed test plots and in nurseries. Offspring of the best-performing plants were tested further, and from these came some of the earliest improved ryegrass varieties.
'Pennfine' and 'Birdie' came from plants found in Southeast Pennsylvania. The most promising plants selected from near the sheep meadow in Central Park in New York City were used to develop 'Manhattan'. 'Citation' and 'All Star' trace much of their genetics to plants selected from Paterson and Riverside parks, respectively, in Baltimore, Md., while 'Pennant' was derived from plants collected from the campus lawn of the University of Maryland. A few additional plants selected from old turfs in New Jersey, Maryland, Missouri, Kentucky, Washington, D.C., as well as some introductions from Europe also contributed to early ryegrass breeding programs.
Ryegrass breeders continued to use plants from the best collections and breeding populations to develop a long-term enhancement program using many cycles of breeding and selection. They aim for high overall turf performance, improved mowing quality, rapid establishment of a full, wear-tolerant turf canopy, pest resistance and stress tolerance.
Each cycle of selection builds on the progress of each previous cycle of selection. This has resulted in a stream of steadily improved varieties showing higher seed yields, lower establishment costs and many improvements in turf performance. Useful endophytes-present in a large proportion of modern varieties-further enhance insect resistance and stress tolerance.
Tall fescue Tall fescue was originally introduced to the United States from Europe by private agriculturists and government personnel during the 1800s. A few of the best-adpated seedlings persisted and survived. Tall fescue was not a prominent grass until the release of 'Alta' and 'Kentucky 31', originating from Oregon and Kentucky, respectively, in the early 1940s. These were used for both pastures and turf.
The ancestors of most of the current American turf-type tall fescues were related to 'Rebel' tall fescue and to attractive plants found growing in old turfs in the Eastern half of the United States during the collection program started in 1962. The precise origin of the seed used to establish these old turfs was unknown.
The tall fescue plants that persisted in these old turfs survived under the stresses of frequent close mowing, heavy traffic, excessive shade, poor soils and the diseases and pests common to our climates. The best plants produced patches that often exceeded 1 meter in diameter, indicating they had survived for many years. A few hundred attractive plants were collected and established in nurseries and trials. All but a few dozen of the most promising plants were quickly discarded.
The best selections from old turfs were different from any tall-fescue variety in existence at the time. They produced lower-growing turfs with finer leaves, higher density, darker color and greater tolerance of close mowing. They most likely originated from the early introductions from Europe. However, it's possible that some of them had 'Kentucky 31' or 'Alta' in their ancestry.
Repeated cycles of selection using intercrosses of the best performing plants and some new sources resulted in lower-growing, darker-green, attractive plants with improved turf performance. Selection was also effective in maintaining high seed yields and good stress tolerance. Substantial progress continues to be made in developing tall fescues. Finer leaves, better disease resistance, increased persistence under close mowing and higher density are some of the qualities driving ongoing efforts.
Fine fescues The fine fescues, as a group, are tolerant of drought, moderately acid soils, low fertility and some shade. Thus, the increasing interest in turfgrasses with good performance under low maintenance has stimulated breeding programs for Chewings, strong creeping red, hard, blue, slender creeping and sheep fescues.
As with other turfgrasses, the best-adapted and most-competitive fine fescues are likely to persist and thrive in old turfs. Thus, collection efforts have focused on old turfs from which fine fescues can be selected for genetic improvement.
Bentgrasses The ancestry of many of the creeping, colonial and velvet bentgrass plants used in American turfgrass breeding programs traces to plantings of South German mixed bentgrass seed used on golf courses in the late 1800s and early 1900s. Much of this seed came from farmers in central Europe who supplemented their income by harvesting seed from unmowed bentgrasses on roadsides and uncropped areas.
Selection programs for bentgrass focus on old greens, where decades of close mowing have favored plants well-adapted to greens conditions. The best specimens collected from these old turfs are proving to be much better adapted to the climates and pests of the United States than recent collections from Europe.
'Penncross', released in the mid-1950s, became the predominant greens bentgrass and remains popular today. It was a product of vegetatively propagated bentgrasses that had been selected from old South German greens. Today, many greens seeded to improved bentgrasses are several years old and, like the old South German greens before them, are proving to be fertile hunting grounds for breeders in search of superior varieties. Bentgrasses released during the past decade, selected from old turfs and population improvement programs, exhibit even higher densityas well as much-improved tolerance to close mowing, diseases and environmental stresses.
Kentucky bluegrass Joseph Valentine, superintendent of the Merion Golf Course near Philadelphia, Pa., discovered 'Merion' Kentucky bluegrass, in the early 1930s. He sent a sample to the researchers at the Arlington Turf Garden, where it exhibited excellent performance. It was subsequently released and become a landmark variety in many countries.
Nearly 98 percent of the 150 trillion seeds of 'Merion' produced and used since its release have or can produce a plant genetically identical to the plant discovered by Joseph Valentine. That's because Kentucky bluegrass undergoes what is known as apomictic reproduction, which means that it can produce seed without fertilization. Nearly all seed produced by an apomictic plant is genetically identical to the parent. It is a natural version of cloning.
With apomictic reproduction, hybrids between Kentucky bluegrass varieties can be multiplied by seed. Thus, if you can get a successful hybrid, apomictic reproduction allows you to easily develop it into a marketable variety with the genetic advantages of hybrid vigor plus the ease of propagation by seed.
Breeders have been able to develop a vast range of adaptation among Kentucky bluegrass varieties. In fact, if you look at Kentucky bluegrasses collectively, you'll find virtually every characteristic desired in an elite lawngrass for temperate regions. Turfgrass breeders are still trying to combine all these useful characteristics in a single variety. Though breeders have become better at cross-pollinating Kentucky bluegrass, it remains a relatively difficult process compared to other grasses.
Warm-season grasses Zoysiagrass, bermudagrass and St. Augustinegrass traditionally have been the primary warm-season species used in the United States.
* Zoysiagrass was first introduced in this country in the late 1800s. 'Meyer', an improved variety of Zoysia japonica with good texture, color and vigor, was released in the 1950s and has remained the most well-known and -used variety of zoysiagrass. Since that time, relatively few new varieties have been developed. However, recent breeding efforts aimed at creating seeded types have been successful, overcoming the major drawback of slow establishment by sprigging or sod.
* Bermudagrass has been grown in the United States for centuries, and is one of the most widely used grasses in the world. If fact, it's exact origin is not known with certainty because it has been so widespread for so long.
Common bermudagrass is grown widely. For decades, it was the only seeded type available. However, several improved seeded selections now are available and breeding efforts are focusing on creating seeded varieties similar to the elite triploid hybrids.
The improved triploid hybrids are propagated vegetatively. Fine-textured hybrids-notably 'Tifgreen' and 'Tifway' (released in the 1950s), and 'Tifdwarf' (1960s)-have been available for putting green use for many years. More recent selections are even more finely textured.
* St. Augustinegrass has been grown as a turfgrass in the continental United States at least since the late 1800s (and much earlier in Hawaii). It is not well adapted to cold and is therefore grown primarily in Southern coastal states. Few significant improvements occurred prior to the introduction of 'Floratam' in the 1970s. 'Floratam' was selected for resistance to the emerging problems of chinch bugs and St. Augustinegrass Decline virus (SAD).
Many strains of St. Augustinegrass are not fertile, so this species has primarily been vegetatively reproduced. Some work has been done to develop seeded types, but they remain little used. Finer texture and improved cold tolerance are other characteristics that breeders are attempting improve in St. Augustinegrass.
New germplasm needed Recent releases and current selections suggest that dramatic progress is still possible in the improvement of turfgrasses. Unfortunately, current programs are working with limited genetic resources. Recent attempts to collect new genetic material in Europe, Asia and South America should be expanded. These efforts may provide the genetic diversity necessary to take turfgrasses to a new level of quality. Turfgrass breeding is in its infancy compared to the genetic improvements made in our major food crops and domesticated animals. The best is still to come!
Part II: Where we're going. The turfgrass seed industry is larger than ever and still expanding. The number of new variety introductions has mushroomed during the past couple of decades. However, as quickly as new products are developed, additional challenges arise: new diseases and insects, extreme weather conditions, reduced efficacy or discontinuation of traditional pest-control products. Also, the environmental awareness of the general public causes greater scrutiny of pesticide, water and fertilizer use on turfgrass. Factors such as these keep pressure on breeders to create new varieties that are more pest-resistant, stress-tolerant, durable, attractive and inexpensive to maintain.
Cool-season grasses Efforts to improve cool-season grasses are increasing, despite the existence of several hundred commercially available varieties.
* Kentucky bluegrass (Poa pratensis) is experiencing a resurgence as research focuses on qualities such as tolerance to low mowing heights for fairway use, low maintenance needs and drought tolerance. Another consideration is improving seed yields. This is especially important now that field burning has been reduced or eliminated in most seed production areas for reasons of safety and air quality.
* Perennial ryegrasses (Lolium perenne) in the current National Turfgrass Evaluation Program (NTEP) trials are darker green and denser than ever. Varieties containing endophytes exhibit excellent insect resistance while advances have been made in tolerance to brown patch and dollar spot as well. However, overall disease susceptibility is still a problem, with Pythium blight and, particularly, gray leaf spot as the major concerns. As reductions in pesticide use become more imperative, perennial ryegrass varieties will need improved disease resistance.
* Tall fescue (Festuca arundinacea) varieties, like perennial ryegrass, exhibit higher quality than in the past, mainly due to a darker-green color and denser, more-uniform growth habit. These newer tall fescues also perform well under varying management levels, from low to high. However, brown patch continues to be the nemesis of tall fescue. Only moderate resistance or tolerance to brown patch is found in the best varieties or experimental selections. Therefore, true resistance may require the movement of a gene for resistance from another plant species to tall fescue using genetic engineering.
* Fineleaf fescues are a broad category that includes six Festuca species. These grasses have been improved more than any other cool-season grasses. Initial data indicate that several chewings fescues (Festuca rubra var. commutata) are outperforming hard fescue varieties (Festuca ovina var. duriuscula). In addition, several strong creeping red fescues (Festuca rubra) are exhibiting excellent initial quality.
Even though the fineleaf fescues are providing better quality and persistence than ever before, they still have limitations. Traffic tolerance and mowing during summer heat can be problems, and nitrogen levels must be kept low to ensure survivability. Nevertheless, we can expect to see fineleaf fescues make their way more into low-maintenance, low-impact sites such as non-irrigated lawns and golf-course roughs.
* Bentgrasses provide high-quality turf but require significant management inputs. Although breeding has led to new creeping bentgrasses (Agrostis stolonifera) that provide higher-quality, denser putting surfaces, these tend to require more cultural management, not less. Therefore, efforts are underway to improve disease and insect resistance. For fairways, creeping bentgrass is replacing perennial ryegrass in many areas because bentgrass has lower pesticide requirements than perennial ryegrass. Velvet bentgrass (Agrostis canina), known for its disease resistance and fine-leaved, dense growth, is being improved for use in the more northern locations. Colonial bentgrass (Agrostis tenuis) has disease-resistance characteristics that have prompted breeders to develop varieties for fairway use.
Warm-season grasses In warm-season grasses, the main breeding emphasis has been on bermudagrass (Cynodon spp.) development. Many new seeded and vegetatively propagated varieties have been developed with improved qualities. Some of the newer seeded bermudagrasses are finer-textured and denser, approaching the quality of the better vegetative varieties. This is important because the seeded varieties are faster and less expensive to establish than the vegetative types. Improving bermudagrass seed yield is another major focus of breeders.
Certain vegetative bermudagrasses with faster establishment and better disease and insect resistance are either close to commercialization or are in commercial production. Several very fine, dense "ultradwarf" varieties are recent additions to the marketplace. These "ultradwarfs" are being planted on putting greens in the southern United States, often to replace old 'Tifdwarf' bermudagrass or creeping-bentgrass greens. Data collected from trials and anecdotal evidence from superintendents indicate these grasses are performing well.
Research continues on other warm-season species such as buffalograss (Buchloe dactyloides), zoysiagrass (Zoysia spp.), St. Augustinegrass (Stenotaphrum secundatum) and centipedegrass (Eremochloa ophiuroides). Each has its own niche area for use.
* Buffalograss is drought tolerant but susceptible to disease and weed-infestation problems in the more humid eastern states. Therefore, its main use has been west of the Mississippi River on low-maintenance lawns, roadsides and golf course out-of-play areas.
* Zoysiagrass is being used more on fairways and tees by superintendents wanting to reduce pesticide and water use. New seeded zoysiagrasses significantly reduce establishment time, which traditionally has been a major drawback with zoysiagrass.
* St. Augustinegrass is still the major homelawn grass in Florida and the Gulf Coast areas but winterkill and lack of true drought tolerance are problems. Development of more attractive, finer-textured, lower-growing types is occurring, but these types seem to be less winter-hardy. Therefore, cold tolerance is a primary focus of breeders.
* Centipedegrass is attracting somewhat more attention than in past years, but there still are few commercially available varieties. Centipedegrass will survive under very low fertility levels and minimal irrigation in the Southeast, but iron chlorosis in spring is a problem, along with winterkill.
New species and native habitats In addition to breeding efforts with traditional species, breeders are investigating new species and reinventing old ones. These new efforts are not likely to produce a grass with the impact of Kentucky bluegrass or perennial rye. Rather, they will be well-suited to specific uses or conditions.
Tufted hairgrass (Deschampsia caespitosa) and prairie June grass (Koeleria cristata) are low-maintenance, native U.S. species that are now commercially available. Hybrids between native Texas bluegrass (Poa arachnifera) and Kentucky bluegrass have performed well in the hot, southeastern United States. Idaho bentgrass (Agrostis idahoensis) has been released as a possible fairway grass. Seashore paspalum (Paspalum vaginatum) is very salt tolerant, thriving even when irrigated with ocean water. It has been improved for use on tees, greens, fairways and athletic fields, and several varieties should be commercially available in the near future. Saltgrass (Distichlis spp.) is also very salt tolerant, as well as drought tolerant, and is being considered for further improvement. Seashore zoysiagrass (Zoysia sinica) may be useful in acid soils where salty or effluent water is required for irrigation.
Annual bluegrass (Poa annua) has been a nemesis of golf course superintendents for many years. However, because many greens are more Poa annua than bentgrass, and that Poa annua can produce an excellent putting surface, it makes sense to work with annual bluegrass instead of against it. Improved varieties are under development, and one is already in commercial production.
New technology Some of the most fascinating research in turfgrass variety development has come in the area of genetic engineering. Compared to other crops, this work is in its infancy regarding turfgrass. Therefore, the main effort thus far has been on transferring some of the easier traits from traditional crops. Herbicide resistance, using glyphosate or glufosinate, has been incorporated into creeping bentgrass using genetic engineering, with other species such as buffalograss, Kentucky bluegrass and zoysiagrass in the works. This technology allows a user to spray a non-selective herbicide "over-the-top," killing weeds and other grasses but not the turf.
One of the potential problems of this technology is the possible escape of the resistance gene to other weedy grass species through cross-pollination. This phenomenon is currently being researched, and it's too early to determine the true risks. But if this turns out to be a serious problem, seed production or actual use may be limited. Some breeders are working at incorporating herbicide resistance using traditional breeding with the hope of providing resistance to non-selective herbicides without gene transfer.
The transfer of other traits such as drought and salt tolerance, disease and insect resistance and low growth habit are possible using genetic engineering. Some of this research already is underway in turfgrass. However, certain of these attributes are relatively difficult to transfer from one organism to another. This research consumes considerable time and money, much of which is not yet available to scientists working with a non-traditional crop such as turfgrass. Thus, although the possibilities seem limitless, turf managers shouldn't expect too many advances from genetic engineering in the near future.
Environmental and societal pressures will increase the demand for more "eco-friendly" turfgrasses. Therefore, we can expect breeders to emphasize development of turfgrasses that better survive heat, cold, drought, diseases, insects, traffic and other stresses with fewer inputs.
Genetic engineering will be used more and more to achieve these goals, but it is only one of the tools that plant breeders can use. Traditional plant breeding techniques, such as hybridization and population improvement, along with new collections of wild, hardy types will continue to be the main focus of breeders. With additional emphasis on breeding and more individuals and companies involved in turfgrass improvement, turf managers will benefit by having more and better grasses to choose from.
Dr. C. Reed Funk is professor of agronomy at Rutgers University (New Brunswick, N.J.) and Kevin Morris is executive director of the National Turfgrass Evaluation Program (Beltsville, Md).
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