Abstract
A maximum likelihood approach of half tetrad analysis (HTA) based on multiple restriction fragment length polymorphism (RFLP) markers was developed. This procedure estimates the relative frequencies of 2n gametes produced by mechanisms genetically equivalent to first division restitution (FDR) or second division restitution and simultaneously locates the centromere within a linkage group of RFLP marker loci. The method was applied to the diploid alfalfa clone PG-F9 (2n = 2x = 16) previously selected because of its high frequency of 2n egg production. HTA was based on four RFLP loci for which PG-F9 was heterozygous with codominant alleles that were absent in the tetraploid tester. Models including three linked and one unlinked RFLP loci were developed and tested. Results of the HTA showed that PG-F9 produced 6% FDR and 94% second division restitution 2n eggs. Information from a marker locus belonging to one linkage group was used to more precisely locate the centromere on a different linkage group. HTA, together with previous cytological analysis, indicated that in PG-F9, FDR 2n eggs are likely produced by diplospory, a mechanism common among apomictic species. The occurrence of FDR 2n eggs in plant species and their importance for crop evolution and breeding is discussed together with the potential applicability of multilocus HTA in the study of reproductive mutants.
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- Anderson E G. Crossing over in a Case of Attached X Chromosomes in DROSOPHILA MELANOGASTER. Genetics. 1925 Sep;10(5):403–417. doi: 10.1093/genetics/10.5.403. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Chakravarti A., Slaugenhaupt S. A. Methods for studying recombination on chromosomes that undergo nondisjunction. Genomics. 1987 Sep;1(1):35–42. doi: 10.1016/0888-7543(87)90102-9. [DOI] [PubMed] [Google Scholar]
- Cui X., Gerwin J., Navidi W., Li H., Kuehn M., Arnheim N. Gene-centromere linkage mapping by PCR analysis of individual oocytes. Genomics. 1992 Jul;13(3):713–717. doi: 10.1016/0888-7543(92)90146-j. [DOI] [PubMed] [Google Scholar]
- Da Y., Jarrell V. L., Wang T., Fernando R. L., Wheeler M. B., Lewin H. A. Multilocus analysis for gene-centromere mapping using first polar bodies and secondary oocytes. Genetics. 1995 Feb;139(2):1091–1097. doi: 10.1093/genetics/139.2.1091. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Echt C. S., Kidwell K. K., Knapp S. J., Osborn T. C., McCoy T. J. Linkage mapping in diploid alfalfa (Medicago sativa). Genome. 1994 Feb;37(1):61–71. doi: 10.1139/g94-008. [DOI] [PubMed] [Google Scholar]
- Jarrell V. L., Lewin H. A., Da Y., Wheeler M. B. Gene-centromere mapping of bovine DYA, DRB3, and PRL using secondary oocytes and first polar bodies: evidence for four-strand double crossovers between DYA and DRB3. Genomics. 1995 May 1;27(1):33–39. doi: 10.1006/geno.1995.1005. [DOI] [PubMed] [Google Scholar]
- Nel P. M. Crossing over and Diploid Egg Formation in the Elongate Mutant of Maize. Genetics. 1975 Mar;79(3):435–450. doi: 10.1093/genetics/79.3.435. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Rhoades M. M., Dempsey E. Induction of chromosome doubling at meiosis by the elongate gene in maize. Genetics. 1966 Aug;54(2):505–522. doi: 10.1093/genetics/54.2.505. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Sherman F., Wakem P. Mapping yeast genes. Methods Enzymol. 1991;194:38–57. doi: 10.1016/0076-6879(91)94006-x. [DOI] [PubMed] [Google Scholar]