Inheritance of the Flower Types of Gerbera hybrida

Abstract

Cultivated gerbera daisies [Gerbera hybrida (G. jamesonii Bolus ex Adlam × G. viridifolia Schultz-Bip)] have several different flower types. They include single and crested cultivars that have normal florets with elliptical (ligulate) outer corolla lips and spider cultivars that have florets with laciniated (split) outer corolla lips appearing as several pointed lobes. The objective of this investigation was to determine the mode of inheritance of the major flower types of gerberas in the North Carolina State Univ. collection. The collection contained parents and four generations of progeny representing a wide range of single and crested cultivars and some spider cultivars. Genotypes of parents used in crosses were determined by testcrosses to single-flowered, ligulate floret cultivars similar in phenotype to the wild, parental gerbera species. Testcrosses indicated that the wild type was recessive to the crested and spider flower types and given the genotype crcrspsp. For each of the types, a series of crosses were made to produce PA, PB, F1, F2, BC1A, and BC1B progeny. Allelism was tested operationally by crossing genotypes in all possible combinations and observing single-gene-pair ratios. Linkage relationships among the crested and spider loci were tested using dihybrid crosses and testcrosses. Phenotypic segregation ratios suggested the presence of two dominant alleles, Crd and Cr, determining the enlarged disk and trans floret, male-sterile and enlarged trans floret, male-fertile crested types, respectively, and an unlinked dominant gene, Sp, determining the spider type. Dominance appeared to be incomplete due to the reduction of trans floret length in most Crdcr and Crcr heterozygotes compared to crested homozygotes and the appearance of the quasi-spider type (spider trans and disk florets and ligulate and/or slightly notched ray florets) among certain crested Spsp heterozygotes.