Submitted to: Plant and Animal Genome VX Conference Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 10/17/2001
Publication Date: 2/3/2002
Technical Abstract: The difficulty in accurately determining the reproductive behavior of plants hinders molecular studies of apomixis. Cytological examinations of megagametophyte development and field-based progeny tests are labor intensive. The cost of these methods results in smaller mapping populations(i.e. map resolution) and fewer megagametophyte/progeny evaluations (i.e. phenotypic precision). Utilizing an established genome map of buffelgrass, we have identified cDNA-derived RFLP fragments that are equivalent to the alternate alleles of a gene pair(Aa). These markers follow simple Mendelian genetics and segregate 1:1 in the progeny. Primers were developed for the allelic fragments of each cDNA. Genomic DNA of 200+ progeny from a plant of each reproductive class (obligate sexual, obligate apomict, and facultative apomict) was extracted and screened with each primer set in 96-well plates. For each fragment that the obligate sexual genotype possesses, segregation results in its transmission to 50% of the progeny. In contrast, each fragment that the obligate apomictic genotype possesses is transmitted to 100% of its progeny. In the facultative apomictic genotype , parental fragments are transmitted to 50% of its sexually-derived progeny and 100% of its apomictically-derived progeny. Each percent of progeny in excess of 50% that possess parental fragments hypothetically corresponds to a 2% occurrence of apomixis. Megagametophyte development was observed and classified in more than 200 ovules from each reproductive class. Comparison of the cytological and PCR methods, as well as the utility of the PCR method for QTL mapping of apospory in buffelgrass, will be discussed.