Progress 10/01/00 to 09/30/05
Outputs
One of the objectives of this study was to determine the mode of inheritance of the major flower types of Gerbera hybrida. 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. They indicated that the single(wild-type) flower type was recessive to the crested and spider flower types and was 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. 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 among certain crested Spsp heterozygotes. A second objective was to determine the mode of inheritance of a glossy leaf type having very low numbers of bristle macrohairs (MHs) on the adaxial leaf surface compared to the wild type. Phenotypic segregation ratios suggested the presence of a dominant allele, Mhd, determining low density of adaxial bristle MHs and moderate reduction in abaxial smooth MHs. This gene was unlinked to the powdery mildew (PM) resistance gene, Pmr1, identified earlier in a parallel study. The Mhd allele appeared to be incompletely dominant in some heterozygotes. Density of leaf MHs did not affect PM resistance. A third objective was to determine the mode of inheritance of dark (brown, brown-black, black-purple, or black) color in the central disk of flowers of certain gerbera cultivars. Wild-type flowers have green-yellow, yellow-green, or light yellow central disks. Phenotypic segregation ratios indicated that dark disk color
was determined by a single dominant gene, designated Dc. Dominance appeared to complete. A fourth objective was to determine the nature and inheritance of an apple-like fragrance discovered in a line of our NCSU gerbera population. The moderate fragrance exhibited was due to the emission of substantial quantities of methylbutanoic acid methyl ester (methyl-2-methyl butyrate), a compound also produced by apples. On the other hand, wild-type, non-fragrant flower types either failed to produce detectable quantities of this methyl ester or produced very low quantities of this compound. Phenotypic segregation ratios suggested that fragrance was determined by a single dominant gene, Fr.
Impacts
The large breeding collection of Wolfpack Country Gerberas has been made available to some major seed companies, including Daehnfeldt and Sakata Europe. Seeds from plants of this collection have been made available to Sakata Europe and for a time to the public by Park Seed Co. The collection was developed for increased resistance to heat, powdery mildew, and crown and root rot over that currently available to the grower and nurseryman. It contains the widest variety of flower types and colors. Our addition of apple fragrant gerberas adds a new dimension to gerbera floraculture. The information gained by our genetic studies will provide the breeder with direction for designing new cultivars exhibiting various combinations of desired traits.
Publications
- Kloos, W.E., C.G. George, and L.K. Sorge. 2005. Dark disk color in the flower of Gerbera hybrida is determined by a dominant gene, Dc. HortScience 40:1992-1994.
- Kloos, W.E., C.G. George, and L.K. Sorge. 2005. Inheritance of powdery mildew resistance and leaf macrohair density in Gerbera hybrida. HortScience 40:1246-1251.
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Progress 10/01/03 to 09/30/04
Outputs
Gas chromatographic-mass spectrophotometric analysis of fragrance in Gerbera hybrida was continued on two backcrosses and one F2 generation. Results demonstrated phenotypic ratios of 3 fragrant:1 non-fragrant for the F2 and 1:1 for the BC2 generations. The total number of progeny was 33 for the F2 generation and, hence, additional crosses were made to provide an additional 120 progeny for the chi-square test. Some progeny are producing flowers this year, and additional progeny will be producing progeny in late spring of next year. Several plants producing a relatively strong apple fragrance will be tested to determine if they are homozygous for the suspected fragrance gene. If they prove to be homozygotes, they will be chosen as possible parents for introducing fragrance to a variety of different gerbera flower types and colors. In August and September of this year, we again observed several plants producing a maple syrup odor. The unusual appearance of this odor was
associated with premature senescence of certain flowers. The cause is still under investigation, though it can be initiated by either Penicillium infection or in the absence of infection by unusually hot humid days. We will be investigating the effects of ethylene on odor next year.
Impacts
The large breeding collection of Wolfpack Country Gerberas has now been made available to major seed companies, including Daehnfeldt and Sakata. The collection was developed for increased resistance to heat, powdery mildew, and crown and root rot over what was currently available to the grower or nurseryman. The collection contains a wide variety of flower morphotypes and colors. The discovery of fragrant gerberas adds a new and exciting dimension to gerbera floraculture. The fruity fragrance is quite similar to that of apples.
Publications
- Kloos, W.E., C.G. George, and L.K. Sorge. 2004. Inheritance of the flower types of Gerbera hybrida. J. Amer. Soc. Hort. Sci. 129:802-810.
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Progress 10/01/02 to 09/30/03
Outputs
The NCSU plant collection designated "Wolfpack Country Gerberas" developed by the principal investigator during this project has now been transferred and made available to Daehnfeldt and Sakata for breeding purposes and commercial use. A large seed collection obtained from the above plants and designed for breeding purposes is being made available to Sakata in the near future. Fragrant gerberas were discovered earlier in our breeding program and analyzed chemically and genetically. Results of a collaborative gas chromatographic-mass spectrophotometric analysis of flowers indicated that the major fragrance compound giving a fruity odor is a methylbutanoic acid methyl ester. Fragrance appears to be due to the presence of a dominant gene as suggested by the phenotype ratios of progeny obtained from F2 (3:1) and backcrosses (1:1). Because the wild-type, non-fragrant gerbera produces very low quantities of the above compound compared to mutant fragrant gerberas, we suspect
that the role of the dominant gene is one of upregulation. During hot, humid summer months a few flowers produced in addition to the above compound a pentenone and methyl butanol giving flowers a maple syrup odor. The unusual appearance of these latter compounds is currently under investigation.
Impacts
The large breeding collection of Wolfpack Country Gerberas has now been made available to major seed companies, including Daehnfeldt and Sakata. The collection was developed for increased resistance to heat, powdery mildew, and crown and root rot over what was currently available to the grower or nurseryman. The collection contains a wide variety of flower morphotypes and colors. The discovery of fragrant gerberas adds a new and exciting dimension to gerbera floraculture. The fruity fragrance is quite similar to that of apples.
Publications
- No publications reported this period
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Progress 01/01/02 to 12/31/02
Outputs
Selection of heat- and water-resistant Gerbera cultivars was continued this year by the growth of potted plants in full sun (in the greenhouse during winter and outside on black landscape cloth during spring, summer, and fall) receiving the equivalent of 5-7 cm (3-4 liters) of water daily. This summer was one of the hottest on record in North Carolina. Temperatures in the sun often exceeded 100 degrees C. Ninety-two percent of cultivars selected for breeding on the basis of disease resistance, flower morphological and color traits, leaf traits, and fragrance survived the selection pressure. Several new cultivars exhibiting superior growth and floriferousness during these trials have been successfully cloned. The breeding cultivar collection will become available for commercial use in the near future.
Impacts
Our wide range of different color, flower, and leaf types of Gerberas is continuing to be developed for resistance to heat, powdery mildew, and crown and root rot so that hardiness as a perennial can be improved significantly over that found in currently available stock. These combined features will make the Gerbera daisy an attractive and hardy plant for use as a cutflower in the garden and in landscapes. We have introduced the Wolfpack Country Gerbera to the nursery industry by providing seeds for distribution by Park Seed Company. These seeds originated from our best crosses and superior cloned cultivars.
Publications
- No publications reported this period
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Progress 01/01/01 to 12/31/01
Outputs
We have identified alleles determining two different shades of red flower color, dark or cardinal red (RHS) vs. bright or post office red (RHS), and the several loci controlling flavanoid production. As a result of numerous test crosses, we have selected cultivars that are homozygous for the various traits we wish to perpetuate in our line of Wolfpack Country Gerberas. These include flower morphological and color traits, disease resistance, and leaf characteristics. Crosses with our fragrant lines suggest that fruity and sweet fragrance are controlled by alleles that are dominant to the common allele associated with non-fragrance, although the intensity of the fragrance in heterozygotes is quite variable ranging from moderate to light. With the improvement of cloning techniques, we have now cloned 43 of our superior cultivars, many of which have been tested under field conditions this year.
Impacts
Our wide range of different color, flower, and leaf types of Gerberas are being developed for resistance to powdery mildew and crown and root rot so that hardiness can be improved significantly over that found in currently available stock. These combined features will make the Gerbera daisy an attractive and hardy plant for use as a cutflower in the garden and in landscapes. The nursery industry in North Carolina has been growing rapidly over the past ten years. We have introduced the Wolfpack Country Gerbera to the nursery industry by providing seeds from outstanding crosses and superior cloned cultivars through micropropagation.
Publications
- No publications reported this period
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Progress 10/01/99 to 09/30/00
Outputs
n/a
Impacts
(N/A)
Publications
- No publications reported this period
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