CO-SEGREGATION OF THE GYNOMONOECIOUS SEX FORM1 GENE (GSF1) OF TRIPSACUM DACTYLOIDES (POACEAE) WITH MOLECULAR MARKERS

The only monogenic trait in Tripsacum to date was first identified in the prolific sex form variant Tripsacum dactyloides (L.) L. forma prolificum Dayton et Dewald. The expression of this trait is controlled by the presence of a single-gene, recessive pistillate mutation hereby designated the gynomonoecious sex form1 gene (gsf1), after the registered plant germplasm accession GSF-I (PI483447) from which it was first identified. This trait confers a high degree of feminization to the primarily male floral structure of the Tripsacum rachis. Two molecular markers were found to co-segregate with the gsf1 gene in a diploid (2n = 36) F-2 population of Tripsacum dactyloides, where the female parent (GSF-I) had been previously determined to be homozygous recessive for the gene. Phenotypic scoring data were compared with restriction fragment length polymorphism data and linkage relationships were determined. The gsf1 gene is located similar to 7 cM from tda48, a Tripsacum-derived molecular marker, and similar to 9 cM from npi286, a maize-derived molecular marker. The marker npi286 also maps within similar to 5 cM of the tassel seed2 locus (ts2) of maize, which confers a similar change in the inflorescence of the maize tassel.