Proc. 57th Southern Pasture and Forage Crop Improvement Conference, Athens, GA April 23-25, 2002
Breeding Tall Fescue, Alfalfa, and White Clover in Georgia
Joe Bouton
Department of Crop and Soil Sciences
University of Georgia
Perennial grasses such as endophyte infected tall fescue (Festuca arundinacea Schreb.), bermudagrass (Cynodon dactylon L.), and bahiagrass (Paspalum notatum Flugge) are the predominate forages in pastures of the southeastern United States. The grasses are very dependable and easy to manage and form the base for pasture programs in the region. However, they do have limitations of low nutritive quality, toxicity (e.g. tall fescue), and an off-season where they are non-productive. Since 1977, our forage breeding program has concentrated on improving the tall fescue grass base by developing persistent cultivars that do not produce toxic alkaloids. Another main objective has been to develop cultivars of alfalfa (Medicago sativa L.) and white clover (Trifolium repens L.) that can help mitigate the problems of this perennial grass base.
Alfalfa
In addition to the release of Alfagraze (Bouton et al., 1991), there has been continued development of grazing tolerant alfalfa cultivars by this breeding program (Bouton et. al, 1997a and 1997b). These cultivars range in fall dormancy, are selected to be more adaptable to planting with grasses, and/or contain high levels of disease resistance. They were also developed with the same selection procedure described by Smith and Bouton (1993) and were tested under grazing conditions in both north and south Georgia. In this regard, a new standard test for grazing tolerance was adopted by the North American Alfalfa Improvement Conference (Bouton and Smith, 1998). In order to claim grazing tolerance, a cultivar must perform as well as Alfagraze based on successfully conducting the test. We are now working with commercial alfalfa seed companies to add grazing tolerance to their dormancy specific, multiple pest resistant cultivars. Included in this effort is the development of Round-up Ready grazing tolerant cultivars.
Tall Fescue
Several options have been pursued in our breeding program to either improve cultivars and/or endophytes in order to keep the positive agronomic aspects of infection while reducing toxicity. These include the following: 1) development of persistent E- cultivars; 2) reduce alkaloid levels via selection within current E+ plant/endemic strains populations; 3) selection and re-infection of naturally occurring, non-toxic strains into elite cultivars.
The option of re-infection of UGA cultivars with endophyte strains incapable of producing ergot alkaloids has been our most successful approach. This strategy was previously found to provide better animal performance and stand survival in perennial ryegrass (Lolium perenne) (Fletcher and Easton, 1997) and was speculated to have promise for tall fescue (Latch, 1997). In proof of concept studies, re-infection of two of our tall fescue cultivars, Jesup and Georgia 5, with a naturally occurring endophyte strain incapable of producing ergot alkaloids, AR542, was found to provide better animal performance and stand survival (Bouton et al., 2000; Bouton et al., 2002). The AR542 strain will be marketed in the commercial seed trade as “MaxQ”.
White clover
Most white clover breeding projects in the USA have concentrated on developing cultivars of ladino white clover. Ladino types are high yielding due to their large leaves, but generally possess a low number of stolons compared to the intermediate leaf types that contain high stolon numbers. However, white clover ecotypes collected in Georgia pasture conditions (e.g. grass competition and heavy grazing pressure), even pastures planted previously with ladino cultivars, were found to be exclusively the stolon dense, intermediate leaf types (Bouton and Hoveland, 1996). Initial results indicated one particular germplasm based on ecotypes, GA-43, possessed better stand persistence than the currently used ladino cultivars when tested as renovation legume for grass pastures in the Southeastern USA. The excellent performance of a hybrid between ecotype material and a ladino germplasm (Bouton et al., 1998), now identified as GA-21159, also indicates it will be possible to simultaneously capture the persistence of the ecotypes along with the larger leaf size of the donor ladino parent. These two experimental cultivars, GA-43 and GA-21159, were also found to provide better animal performance due to their increased persistence. These two experimentals are currently being tested across the southern USA in collaboration with University research and extension personnel. Their commercial release is planned for 2003.
References
Bouton, J.H., and C.S. Hoveland. 1996. Using the grazing animal during selection and testing of red and white clover cultivars and germplasms. p. 10. Proc. 14th Trifolium Conf. 21-22 May 1996. Lexington, KY.
Bouton, J.H., C.S. Hoveland, D.R. Woodfield, and J.R. Caradus. 1998. Selection and testing of white clover germplasms derived from naturalized ecotypes. p. 33. Proc. 15th Trifolium Conf. 10-12 June 1998. Madison, WI.
Bouton, J.H., G.C.M. Latch, N.S. Hill, C.S. Hovland, M.A. McCann, R.H. Watson, J.A. Parish,L.L. Hawkins, and F.N. Thompson. 2002. Re-infection of tall fescue cultivars with non-ergot alkaloid producting endophytes. Agron. J. ( In Press).
Bouton, J.H., N.S. Hill, C.S. Hoveland, M.A. McCann, F.N. Thompson, L.L. Hawkins, and G.C.M. Latch. 2000. Performance of tall fescue cultivars infected with non-toxic endophytes. p. 52. Abstracts, 4th International Neotyphodium/Grass Interaction Symposium. 27-29 September 2000. Soest, Germany.
Bouton, J.H., R.N. Gates, D.T. Wood, and P.R. Utley. 1997a. Registration of ‘Amerigraze 702’ alfalfa. Crop Sci. 37:292.
Bouton, J.H., R.N. Gates, D.T. Wood, and P.R. Utley. 1997b. Registration of ‘ABT 805′ alfalfa. Crop Sci. 37:293.
Bouton, J. H., S. R. Smith, Jr., D. T. Wood, C. S. Hoveland, and E. C. Brummer. 1991. Registration of `Alfagraze’ alfalfa. Crop Sci. 31:479.
Bouton, J.H., and S.R. Smith, Jr.. 1998. Standard test to characterize alfalfa cultivar tolerance to intensive grazing with continuous stocking. p. A-8. In C.C. Fox, R. Berberet, F.A. Gray, C.R. Grau, D.L. Jessen, and M.A. Peterson (ed.) Standard Tests to Characterize Alfalfa Cultivars (Third Edition). North American Alfalfa Improvement Conference, Beltsville, MD. Available online at (verified 20 December 2001).
Fletcher, L.R., and H.S. Easton. 1997: The evaluation and use of endophytes for pasture improvement. p. 209-227. In C.W. Bacon and N.S. Hill (eds.). Neotyphodium/Grass Interactions. Plenum Press, New York.
Latch, G.C.M. 1997. An overview of Neotyphodium-grass interactions. p. 1-11. In C.W. Bacon and N.S. Hill (eds.). Neotyphodium/Grass Interactions. Plenum Press, New York.
Smith, S.R., Jr., and J.H. Bouton. 1993. Selection within alfalfa cultivars for persistence under continuous stocking. Crop Sci. 33:1321-1328.