Principles of Plant Genetics and Breeding. George Acquaah
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for their own use. This could be particularly advantageous to poorer farmers in developing countries. In addition, farmers who live in remote regions where government or commercial seed suppliers are not available could essentially guarantee themselves a yearly supply of quality hybrid seed. These farmers would not be dependent on government or commercial seed suppliers once a suitable cultivar was introduced into their area and could provide farmers greater control regarding the production and use of their locally generated product. However, farmers utilizing such “on the farm seed production rational” need to be aware of seed quality issues as well as the enforceable and legal ramifications of selling and or distributing such seed protected by licence, patent, or PVP. Growers should also be aware that the lack of genetic diversity or uniformity that is embedded in their apomictic seed crop could eventually make that variety susceptible to a particular disease infestation. Retaining and sowing an apomictic seed crop over the long term could eventually result in major disease infestations and a dramatic reduction in crop yield.
At this time, it is difficult to visualize how the application of cytogenetics, molecular genetics, mapping, and genetic engineering, coupled with traditional breeding procedures, will be readily integrated to incorporate apomixis into maize and develop a apomictic hybrid corn cultivar anytime in the near future. Some have given the development of apomictic hybrid corn an approximate twenty‐year horizon; others much longer. As has been discussed above, the research process to be utilized to develop apomictic corn, or other species is time consuming, difficult and generates several legal, social, breeding and genetic issues that will need to be resolved. Though the transfer of apomixis holds much promise, it will be some time before a commercial apomictic maize hybrid will reach the marketplace.
References
1 Albertini, E., Barcaccia, G., Porceddu, A. et al. (2001). Mode of reproduction is detected by Parth1 and Sex1 SCAR markers in a wide range of facultative apomictic Kentucky bluegrass varieties. Molecular Breeding 7: 293–300.
2 Bantin, J., Matzk, F., and Dresselhaus, T. (2001). Tripsacum dactyloides (Poaceae): a natural model system to study parthenogenesis. Sexual Plant Reproduction 14: 219–226.
3 Bashaw, E.C. and Hignight, K.W. (1990). Gene transfer in apomictic buffelgrass through fertilization of an unreduced egg. Crop Science 30: 571–575.
4 Blakey, C. A., E. H. Coe Jr., and C. L. Dewald. 1994. Current status of the Tripsacum dactyloides (Eastern gamagrass) RFLP molecular genetic map. Maize Genetics Coop. Newsletter No. 68. University of Missouri, Columbia, MO. pp. 35–37.
5 Blakey, C.A., Goldman, S.L., and Dewald, C.L. (2001). Apomixis in Tripsacum: comparative mapping of a multigene phenomenon. Genome 44: 222–230.
6 Borovsky, M. (1966). Apomixis in intergeneric maize‐Tripsacum hybrids. In: Meeting on Problems on Apomixis in Plants, 8–9. Saratov, Russia: Saratov State University.
7 Borovsky, M. and Kovarsky, A.E. (1967). Intergenus maize‐Tripsacum hybridizations. Izvestia Akademii Nauk Moldovaski, SSR 11: 25–35.
8 Burson, B.L., Voigt, P.W., Sherman, R.A., and Dewald, C.L. (1990). Apomixis and sexuality in eastern gamagrass. Crop Science 30: 86–89.
9 Carmen, J.G. (1997). Asynchronous expression of duplicate genes in angiosperms may cause apomixis, bispory, tetraspory and polyembryony. Biological Journal of the Linnean Society 61: 51–94.
10 Grimanelli, D., Leblanc, O., Espinosa, E. et al. (1998). Mapping diplosporous apomixis in tetraploid Tripsacum: one gene or several genes? Heredity 80: 33–39.
11 Harlan, J.R. and de Wet, J.M.J. (1977). Pathways of genetic transfer from Tripsacum to Zea mays. Proceedings of the National Academy of Sciences of the United States of America 74: 3494–3497.
12 Kindiger, B. (1993). Aberrant microspore development in hybrids of maize x Tripsacum dactyloides. Genome 36: 987–997.
13 Kindiger, B. and Beckett, J.B. (1989). Cytological evidence supporting a procedure for directing and enhancing pairing between maize and Tripsacum. Genome 33: 495–500.
14 Kindiger, B. and Beckett, J.B. (1992). Popcorn germplasm as a parental source for maize x Tripsacum dactyloides hybridization. Maydica 37: 245–249.
15 Kindiger, B. and Dewald, C.L. (1996). A system for genetic change in apomictic eastern gamagrass. Crop Science 36: 250–255.
16 Kindiger, B. and Dewald, C.L. (1997). The reproductive versatility of eastern gamagrass. Crop Science 37: 1351–1360.
17 Kindiger, B. and Sokolov, V. (1997). Progress in the development of apomictic maize. Trends in Agronomy 1: 75–94.
18 Kindiger, B., Blakey, C.A., and Dewald, C.L. (1995). Sex reversal in maize x Tripsacum hybrids: allelic non‐complementation of ts2 and gsf1. Maydica 40: 187–190.
19 Kindiger, B., Sokolov, V., and Dewald, C.L. (1996a). A comparison of apomictic reproduction in eastern gamagrass (Tripsacum dactyloides (L.)) and maize‐Tripsacum hybrids. Genetica 97: 103–110.
20 Kindiger, B., Bai, D., and Sokolov, V. (1996b). Assignment of gene(s) conferring apomixis in Tripsacum to a chromosome arm: cytological and molecular evidence. Genome 39: 1133–1141.
21 Leblanc, O., Griminelli, D., Gonzalez‐de‐Leon, D., and Savidan, Y. (1995). Detection of the apomictic mode of reproduction in maize‐Tripsacum hybrids using maize RFLP markers. Theoretical and Applied Genetics 90: 1198–1203.
22 Leblanc, O., Griminelli, D., Islan‐Faridi, N. et al. (1996). Reproductive behavior in maize‐Tripsacum polyhaploid plants: implications for the transfer of apomixis into maize. The Journal of Heredity 87: 108–111.
23 Li, D., Blakey, C.A., Dewald, C.L., and Dellaporta, S.L. (1997). Evidence for a common sex determination mechanism for pistil abortion in maize and its wild relative Tripsacum. PNAS USA 94: 4217–4222.
24 Maguire, M. (1957). Cytogenetic studies of a Zea hyperploid for a chromosome derived from Tripsacum. Genetics 42: 474–486.
25 Maguire, M. (1960). A study of homology between a terminal portion of Zea chromosome 2 and a segment derived from Tripsacum. Genetics 45: 195–209.
26 Maguire, M. (1962). Common loci in corn and Tripsacum. The Journal of Heredity 53: 87–88.
27 Mangelsdorf, P. C. and R. G. Reeves. 1939. The origin of Indian corn and its relatives. Texas Agric. Exp. Stn. Bull. No. 574.
28 Petrov, D.F., Belousova, N.I., and Sl Fokina, E. (1979). Inheritance of apomixis and its elements in maize x Tripsacum dactyloides hybrids. Genetika 15: 1827–1836.
29 Petrov, D.F., Belousova, N.I., Fokina, E.S. et al. (1984). Transfer of some elements of apomixis from Tripsacum to maize. In: Apomixis and Its Role in Evolution and Breedint (ed. D.F. Petrov), 9–73. New Delhi, India: Oxonian Press Ltd.
30 Poggio, L., Confalonieri, V., Comas, C. et al. (1999). Genomic in situ hybridization (GISH) of Tripsacum dactyloides and Zea mays ssp. mays with B chromosomes. Genome 42: 687–691.
31 de Wet, J.M.J., Timothy, D.H., Hilu, K.W., and Fletcher, G.B. (1981). Systematics of South American Tripsacum (Gramineae). American Journal of Botany 68: 269–276.
32 de Wet, J.M.J., Harlan, J.R., and Brink, D.E. (1982). Systematics of Tripsacum dactyloides (Gramineae). American Journal of Botany 69: 1251–1257.
33 Xu, S.J. and Joppa, L.R. (1995). Mechanisms and inheritance of first division restitution in hybrids of wheat, rye, and Aegilops squarrosa. Genome 38: 607–615.
6.11.1 Objectives of wide crosses
Wide crosses may be undertaken for practical and economic reasons, research purposes, or to satisfy curiosity. Specific reasons for wide crosses include the following:
Economic crop improvementThe primary purpose of wide crosses is to improve a species for economic production by transferring one or a few genes, or segment of chromosomes or whole chromosomes from a donor across interspecific