Chromosome doubling of interspecific hybrids in the Festuca-Lolium complex induced by antimitotic agents colchicine, oryzalin, and trifluralin

Tall fescue (Festuca arundinacea Schreb.) as an important forage grass for livestock production can be improved by hybridization with related species for better palatability and nutritive values. However, such interspecific hybrids are sterile. Chromosome doubling mediated by antimitotic agents provides a useful approach to restore the fertility of F1 hybrids in species including tobacco (Nicotiana L.), maize (Zea mays L.) and rape (Brassica napus L.). To investigate the potential of this approach in tall fescue breeding, different plant materials of tall fescue interspecific hybrids and annual ryegrass were treated with antimitotic agents including colchicine, oryzalin and trifluralin to induce chromosome doubling. Treatment of vegetative tillers, calli and germinating seeds indicated that colchicine was the least toxic agent for plant survival and the most efficient one for chromosome doubling. Although oryzalin and trifluralin were highly effective to induce chromosome doubling, most of the plant materials could not survive the treatments. For all three agents, increases in concentration and treatment time resulted in lower survival rate but higher doubling frequency. Successful use of the chromosome doubling approach depends on a compromise between the toxic effect and doubling efficiency that will produce enough chromosome doubled plants. Therefore, colchicine is superior to oryzalin and trifluralin for in vitro chromosome doubling of tall fescue interspecific hybrids and may be appropriate for restoring the fertility in tall fescue breeding.