Submitted to: American Journal of Botany
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/2/1998
Publication Date: N/A
Interpretive Summary: Guatemala grass, an intergeneric hybrid between wild relatives of maize, is vegetatively propagated as a cultivated forage in tropical mesoamerica, south America and the West Indies. The lack of variation across its wide range of distribution suggests a single hybrid origin of ancient derivation, which may contain the oldest living germplasm of wild relatives sof maize in existence today. Our breeding studies demonstrated that relic genetic combinations, which have been latent for centuries, may be recovered through horizontal gene flow. Several hybrid forms were recovered from Guatemala grass which are of interest from an evolutionary prospective, as well as new germplasm sources for forage and maize improvement.
Technical Abstract: Four viable seeds were obtained from open pollinated clones (M-34445, M- 34450 and M-34455) of Tripsacum andersonii maintained at the USDA-ARS National Germplasm Repository, Miami, Florida. Our objective was to characterize the breeding behavior of the highly sterile T. andersonii and its viable progeny, through breeding, cytological and molecular studies. One of the progeny had 64 chromosomes which is typical of T. andersonii an probably resulted from apomictic reproduction. Karyotypes of three viable progeny indicated a tetraploid Tripsacum genomic constitution (2n=4x= 72) plus a haploid set of Zea (1n=1x=10) chromosomes. Two of these progeny were completely sterile whereas one (95-51) produced approximately 5% seed set when crossed with diploid (2n=36) T. dactyloides. The partially fertile 95-51 produced four progeny, one with 2n = 72 (elimination of 10 Zea chromosomes), two with 2n = 82 (apomictic reproduction) and one with 2n n= 100 (sexual polyploidization). PCR-RAPD analysis verified that T. andersonii accessions from seven countries were genetically uniform, and that its progeny were derived through apomixis and sexual polyploidization. PCR- RAPD analysis confirmed that chromosome elimination, apomixis and sexual polyploidization reproductive behaviors occur in the T. andersonii derivative 95-51.