Proc. 57th Southern Pasture and Forage Crop Improvement Conference, Athens, GA April 23-25, 2002

Breeding Bermudagrass, Bahiagrass and Pearl Millet in the Southeast

Wayne W. Hanna

USDA-ARS

Coastal Plain Experiment Station

Tifton, GA 31793

Outstanding progress has been made in the past through breeding bermudagrass (Cynodon dactylon), bahiagrass (Paspalum notatum), and pearl millet (Pennisetum glaucum) for improved dry matter production, forage quality, palatability, persistence, and pest resistance. These characteristics will continue to be important, but the challenge in the future will be, in addition, to develop forages that maximize profits and are environmentally friendly.

 

Traditional approaches: Major improvements have been made in forage cultivars in the past 40 years. However, opportunities are ‘wide open’ in the future because we know more about the genetics of the species, biochemistry of plant growth and development, and quality factors.

 

Genetic pest resistance will become more important because of:

 

* concerns for human health-food and exposure,

 

* label restrictions for forage crops, and

 

* expense of chemical control-especially on forage in the humid southeast.

 

Dry matter distribution, especially fall forage production is needed. There is a major deficit production of both dry matter and high quality dry matter in the fall. This can be accomplished by selecting for genotypes that do not go dormant as fast in the fall. Major progress in this area has been made in Tifton 85 bermudagrass (Burton et al., 1993). Progress is being made in bahiagrass (Blount and Gates, personal communication).

 

Efficient nutrient and water use. This aspect has not received the attention that it deserves. It will become more important as water is considered a precious resource, fertilizer costs rise faster that livestock prices, and the general public becomes increasingly concerned about water quality, reserves and the environment. Keisling et al, (1990) identified pearl millet genotypes that were more efficient in using Mg. We have found that certain turf bermudagrass hybrids can produce the same turf quality with half the recommended nitrogen (unpublished).

 

Below ground characteristics. More efforts are needed on below ground characteristics such as root development, root and shoot microbe interactions, and nematode resistance. It is usually more difficult to work on these problems. However, concerns for water quality and quantity will enhance the interest in these areas.

 

Forage quality. Improvements in forage quality and digestibility offer some of the greatest opportunities for improving warm-season forages. Genetic variation appears to be large for forage digestibility. Minson (1975) reported on studies that showed 70 to 220 g kg-1 variation for in vitro dry matter digestibility within seven tropical warm-season grasses. Buxton and Casler (1993) reported that lignin concentration appears to be more stable than most of the measures of forage quality and that genetic variation exists for this trait. Cross -linkages among cell wall matrix constituents may be the most limiting factors to forage digestibility.

 

Non-traditional approaches

 

Molecular techniques. We have an excellent opportunities to incorporate genes from other organisms into the warm-season grasses using molecular techniques and cell culture. Genes for drought resistance, pest resistance, herbicide resistance, apomixis, etc could have major impact on warm-season grasses. In the future, it may be possible to move blocks of genes without adverse effects. Like other genetic characteristics, these genes are permanent in the plant. This technology could more easily be incorporated and stabilized into vegetatively propagated and apomictic crops because one does not have to go through a sexual seed cycle.

 

However bright is the future for using molecular techniques, there are as many or more obstacles to overcome to take this technology to the farmer and rancher. Patents on just about every aspect of the molecular approach makes it almost impossible to obtain an agreement to use the technology, especially for a crop that does not promise large dollar returns such as the major row crops. Alfalfa may the exception in forages.

 

Somatic hybridization. I think we are missing a great opportunity to make a major breakthrough in forages (and turf) in the area of somatic hybridization. Think of the impact of a hybrid between bermudagrass and Kentucky bluegrass, fescue, or bentgrass. It could revolutionize the forage and turf industries. If the hybrids depended on seed production, the future would not be too bright. But the hybrids mentioned above could possibly be vegetatively propagated, so pollen and seed sterility would not be a problem (probably an advantage). Are the risks high? Yes. But most of the easy stuff has already been done! Producing somatic hybrids is probably the easiest part. Producing plants from fused protoplasms is probably the most difficult part.

 

Apomixis has been of interest to a large group of scientists and seed companies in recent years. It has been used in buffelgrass and Poa to produce cultivars. However, it has not been used commercially outside of its own species. Efforts have progressed to the BC8 generation in an attempt to transfer it from Pennisetum squamulatum to pearl millet (Hanna, 1995). Although apomixis can ‘help’ wide hybrids to survive and produce seed because the sexual cycle is eliminated, this mechanism also presents some seed set problems. This is especially true when genomes from different species are involved. One of the greatest advantages of apomixis is that it greatly increases the opportunity to use unique gene combinations.

 

Going outside the circle. It is okay to go outside of the circle with our ideas and approaches. Going outside the circle can be risky. However, going outside of the circle will more likely result in a major breakthrough (instead of repeating history).

References Cited

Burton, G.W., R.N. Gates, and G.M.Hill. 1993. Registration of ‘Tifton 85′ bermudagrass. Crop Sci. 33:644-645.

 

Buxton, D.R. and M.D. Casler. 1993. Environmental and genetic effects on cell wall composition and digestibility. p. 685-714. In H.G. Jung et al. (ed.) Forage cell wall structure and digestibility. ASA, CSSA, and SSSA. Madison, WI.

Hanna, W.W. 1995. Use of apomixis in cultivar development. Adv. Agron. 54:333-350.

 

Keisling, T.C., W. Hanna, and M.E. Walker. 1990. Genetic variation for Mg concentration in pearl millet lines grown under Mg stress conditions. J. Plant Nutrition 131371- 1379.

 

Minson, D.J. 1975. Pasture management and animal nutrition. Forage Res. 1:1-10.