Location: Crop Germplasm ResearchTitle: Polyploidy and interspecific hybridization in Cynodon, Paspalum, Pennisetum, and Zoysia
|Hanna, W - University Of Georgia|
|Schwartz, B - University Of Georgia|
Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: 3/15/2016
Publication Date: 7/25/2016
Citation: Hanna, W.W., Burson, B.L., Schwartz, B.M. 2016. Polyploidy and interspecific hybridization in Cynodon, Paspalum, Pennisetum, and Zoysia. In: Mason, A.S., editor. Polyploidy and Interspecific Hybridization for Crop Improvement. Boca Raton, FL: CRC Press. p. 318-338.
Interpretive Summary: This is a chapter that will be published in the book entitled "Polyploidy and Interspecific Hybridisation for Crop Improvement". As the title indicates, this book reports how polyploidy (multiple sets of chromosomes) and wide hybridization (crossing plants belonging to different species) have been used to improve a number of economically important crop plants. This chapter summarizes the progress that has been made in using wide hybridization to cross different warm-season grass species, including those with different chromosome numbers, to develop new and improved turf and forage grasses. These include bahiagrass, bermudagrass, dallisgrass, pearl millet, seashore paspalum, and zoysiagrass. One section in the chapter discusses how polyploid warm-season grasses are produced in nature as well as the benefits that are often realized in polyploid plants. The use of polyploidy as a beneficial breeding tool is also discussed. Another section in the chapter describes how wide hybridization was used to identify the parents of common dallisgrass, a natural hybrid, and reports how this grass originated. This information is valuable in the future improvement of this important forage grass.
Technical Abstract: There are many examples of agronomically or economically important characteristics in wild species, such as disease tolerance or quality, that are difficult to incorporate into related cultivated species due to differences in ploidy levels. Sterility, or at least reduced fertility, is common when wild × cultivated crosses are made, if any hybrids are produced. This is unacceptable when seed yield is of primary concern. However, germplasm can be successfully transferred by using colchicine to double chromosome numbers, developing bridging hybrids, taking advantage of genetic mechanisms controlling chromosome/genome segregation, introducing genetic variation in apomictic species by reconstituting the species, and by using the apomictic mechanism to build new ploidy level from within and between species. When vegetative propagation is possible, as in the case of Cynodon and Zoysia species, the chances of successfully using germplasm from polyploid wild species in a breeding program has a much higher potential. Numerous interspecific Paspalum hybrids have been produced, but none have been released as improved cultivars primarily because of sterility issues associated with the F1 hybrids and vegetative propagation was not practical. However, most hybrids were successfully used to conduct phylogenetic studies to elucidate the genomic relationships between a number of different Paspalum species. Also, two of the three diploid progenitors of apomictic, pentaploid common dallisgrass were identified, and a hypothesis of how this important apomictic biotype originated was proposed. In the future, comparative genomics will likely reveal specific shifts in ploidy level, interchromosomal rearrangements, and major genome restructuring that resulted in the evolutionary separation of the wild and cultivated species that we use in our breeding programs today.