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Title: APOMIXIS IN TRIPSACUM: COMPARATIVE MAPPING OF A MULTI-GENE PHENOMENON

Author
item BLAKEY, CYNTHIA - BALL STATE UNIV.
item GOLDMAN, STEPHEN - UNIV. OF TOLEDO, OH
item Dewald, Chester

Submitted to: Genome
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/21/2000
Publication Date: 3/23/2001
Citation: N/A

Interpretive Summary: Understanding the control of reproductive processes in plants is necessary to overcome barriers which limit the use of distant relatives for crop improvement. Genes which segregate for fertility in eastern gamagrass were mapped and correlated with genes essential for fertility in corn. This information will lead to development of strategies to manipulate useful genes between the wild perennial eastern gamagrass and corn for crop improvement.

Technical Abstract: A relationship has been established between the expression of apomixis in natural polyploids of Tripsacum dactyloides and fertility as measured by percent seed set. Thus, fertility may be reliably used as a defining phenotype for apomixis when scoring the progeny from diploid (2n=2x=36) x tetraploid (2n=4x=72) crosses in Tripsacum. By exploiting the relationship pbetween apomixis and fertility, as defined by seed set, analyses were performed on a set of related second generation triploid populations segregating for apomixis. These populations were derived from sexual (diploid) x apomictic (tetraploid) crosses. Sic out of 25 genome-dispersed RFLP markers co-segregate with fertility. Five of these markers were previously reported and include: php20855, tda48, tda53, umc62, and umc83; and are linked to Tripsacum genetic linkage groups F, I, H, L, and A respectively. Significantly, we report here the synteny relationships of the maize chromosome intervals to Tripsacum that segregate for numerous meiosis-specific and fertility-associated genes. Utilizing RFLP locus comparative mapping based on conservation of chromosome (genic) regions between related species, it may be concluded that the genes controlling fertility have ben preserved in both Tripsacum and maize. A sixth marker, umc166, has also been shown to co-segregate with fertility and is conserved in both grass species. Specifically, umc166 is linked to Tripsacum linkage group D and, by synteny comparison, to the short arm of maize chromosome 5. Encoded within this marked interval is the gene Ameiotic1 (AM1) whose function is required for the initiation of meiosis in both micro- and megaspore mother cells and whose absence of expression in the female is, in all likelihood, a prerequisite for the expression of apomixis.