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Cool-season grasses grow rapidly and initiate flowering when temperatures are moderate. Many of the world's most important forages upon which the animal industry is founded are included in this group. Two conditions are necessary to optimize grassland production: (i) proper management and (ii) use of species and cultivars adapted to the specific climate and forage purpose. Grass breeding is a relatively new science, but in the past 30 yr cultivars have been developed to provide improved feed for livestock, to conserve and improve our soil and water resources, and to provide a primary base for aesthetic and recreational purposes. Because of the diversity of uses, it is difficult, if not impossible, to measure the ultimate benefit of grass cultivars in monetary terms. Indeed, grassland agriculture, including grass cultivars, is the foundation on which life and civilization rest. Grass breeding programs have received low priority in recent years as research budgets have tightened. Unfortunately, fewer breeders are now actively pursuing improvement of the germplasm resources necessary to sustain efficient productivity of vast grassland acreages.
Breeders in the Western region have produced 75 cultivars of warm-season forage grasses; all but 16 are native grasses. Breeders in the Southern region have developed 50 cultivars of 10 adapted warm-season forage grass introductions. Generally, adaptation and yield have been increased, sometimes as much as 100%. Such yield increases with the same inputs greatly improve the efficiency of the livestock industry. The benefits to humanity are difficult to determine because no state or federal agricultural statistics agency collects information on the hectarage planted to warm-season grass cultivars. Cattlemen who have used the improved cultivars have benefited. One example is a Texas cattleman with 1600 ha of Coastal Bermuda grass who said “We'd be out of the cattle business without Coastal.” Progress to date indicates that well supported warm-season forage grass breeding projects in which the breeder obtains the cooperation of animal science and other needed disciplines should be able to increase the yield and efficiency of most warm-season grasses 25 to 50%. Such increases without added inputs will reduce feed costs, increase the cattleman's profits, and lower the prices the consumer must pay for animal products.
Dramatic progress continues to be made in the genetic improvement of a number of cool-season grasses used for turf and conservation. Attractive, durable, persistent cultivars with improved pest resistance, increased stress tolerance, and reduced maintenance requirements are becoming available to the American public. Such cultivars are becoming increasingly important in programs to enhance our physical environment, conserve our soil and water resources, and provide recreation. Advances in both the sciences and art of plant breeding and in associated disciplines are making turfgrass breeders more effective in meeting the needs and wants of humanity.
Warm-season grasses that are used for turf are primarily in the genera Axonopus, Cynodon, Eremochloa, Paspalum, Stenotaphrum, and Zoysia. People in subtropical areas benefit from the recreation, aesthetic, sanitation, and conservation features that those grasses provide. The most widely used warm-season turfgrasses are cultivars selected by public plant breeders, although private efforts have been notable in development and marketing. Breeding has created warm-season turfgrass cultivars that are more utilitarian and less costly to maintain, compared with unselected common strains. Successes of breeding include selection for finer texture (e.g., ‘Tifgreen’ bermudagrasses, Cynodon × magenissii Hurcombe); for insect resistance [e.g. ‘Floratam’ St. Augustinegrass, Stenotaphrum secundatum (Walt.) Kuntze]; and for higher apparent density (e.g., ‘Argentine’ bahiagrass, Paspalum notatum Flügge). Most progress in breeding warm-season turfgrasses has been based on serendipitous creation, and skillful discovery. Further stepwise improvement from past successes is difficult, because there is generally no source germplasm available. Scientists have broadened the knowledge of warm-season grass genetics, but knowledge is still fragmentary in other critical areas. The accurate description and identification of cultivars and their wild relatives are almost nonexistent. Shade tolerance and acceptability under reduced irrigation are of the utmost importance, but have been vexing research problems. Pest resistance, while desirable, must be understood in the context of generalized (horizontal) adaptation to the stress environment. Not enough work has been done to correlate laboratory observed resistance with field level resistance. Future progress will depend upon better knowledge of taxonomy and genetic resources, selection method, and the basis of cultivar adaptation.
Animal performance may depend heavily upon the true feeding value of a forage grass that can be expressed as the nutrients used per unit of time. Breeding of forage grasses to improve animal performance has been documented to be successful in several cases where breeders have selected germplasm for greater leafiness, improved digestibility or palatability per se, and reduced alkaloids. Grass breeders must be alert to the influences of maturation, leafiness, stand condition, environment or environmental adaptation, capacity to mix with high-quality legumes, pest susceptibility, and potential antiquality constituents when they select for feeding value improvement. Yield need not be sacrificed in order to gain quality improvements in many instances, but small sacrifices in yield can be acceptable if quality improvements increase animal performance. Small improvements in digestibility or intake of a grass can result in large differences in animal performance. The influence of antiquality constituents can supersede the influence of digestibility and intake in some grass species. Excellent laboratory methods are available to aid breeders in screening grass germplasm for improved digestibility, reduced fiber-component concentration, and possibly improved intake potential. Near infrared reflectance spectroscopy (NIRS) has great potential as a fast and precise method for screening large numbers of genotypes for most feeding value traits that are quantifiable by current or future chemical, physical, or biological methods. New developments in the areas of cell wall carbohydrates, phenolic compounds, plant anatomy, protein degradability, mastication and particle flow, and other mechanical stability merit careful attention. We need a “bidirectional” selection approach, imaginative selection criteria based on theoretical as well as proven concepts, and an interdisciplinary research effort to hasten progress in breeding improved grasses to maximize animal performance.
Plant breeding, including grass breeding, involves taking a raw product, plant germplasm, and improving or adding value to that germplasm by manipulating its genetic composition. The value added to the germplasm has a cost. It usually costs in excess of $100 000/yr to maintain a viable, ongoing grass breeding program. The output of a grass breeding program, i.e., the released cultivars and germplasm, should have an economic value in excess of the cost of the breeding program. Grass breeding programs have produced products such as ‘Coastal’ bermudagrass [Cynodon dactylon (L.) Pers.] where the economic value has greatly exceeded the input cost. Grass breeders have the opportunity to make additional major contributions to the welfare and benefit of future generations of humanity if research goals are carefully delineated and innovative, cost-effective breeding methods are used.
