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 prol ificum Dayton et Dewald. The expression of this trait is controlled by the presence of a single-gene, recessive pistillate mutation hereby d esignated the gynomonoecious sex form1 gene (gsf1), after the register ed plant germplasm accession GSF-I (PI483447) from which it was first identified. This trait confers a high degree of feminization to the pr imarily male floral structure of the Tripsacum rachis. Two molecular m arkers 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 frag ment length polymorphism data and linkage relationships were determine d. The gsf1 gene is located similar to 7 cM from tda48, a Tripsacum-de rived molecular marker, and similar to 9 cM from npi286, a maize-deriv ed molecular marker. The marker npi286 also maps within similar to 5 c M of the tassel seed2 locus (ts2) of maize, which confers a similar ch ange in the inflorescence of the maize tassel.