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R.J. Griesbach

Kangaroo paw is a new cut flower crop native to Australia. There are several interspecific hybrids with improved flower colors, heat tolerance, and growth habit. These hybrids are sterile due to divergent evolution of the parent species. Colchicine was used to double the chromosome number of one important sterile hybrid. This hybrid is everblooming. dwarf. and heat tolerant. The resulting allodiploid was fertile, and progeny are now being evaluated.

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R.J. Griesbach

The flavonoids from flowers of transgenic Petunia ×hybrida Vilm. plants containing the Al gene from Zea mays L. were characterized. The A1 gene encodes the enzyme dihydroflavonol reductase and was introduced into a mutant petunia defective for this gene. Control, nontransgenic plants produced flowers that contained ≈ 50 ng anthocyanin/100 mg tissue dry weight. Anthocyanin distribution was 63% cyanidin, 28% delphinidin, and 9% pelargonidin. In contrast, the transgenic plants produced flowers that contained ≈ 500 ng anthocyanin/100 mg tissue dry weight, with 34% as cyanidin, 12% as delphlnidin, and 54% as pelargonidin. The increase in anthocyanin production in the transgenic plants resulted in a corresponding molar decrease in flavonol accumulation.

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R.J. Griesbach

The apical meristems of Calanthe orchid embryos were exposed to 1 mg/ml pBI-121 DNA in an electric field. pBI-121 contains the GUS marker gene glucoronidase under the control of the 35 S cauliflower mosaic virus promoter. A pipette containing 0.3% agarose and acetate buffer containing the DNA was placed on one end of the embryo; while the opposite end was in contact with a pipette containing only buffer and agarose. Uptake of the DNA into the meristem was monitored by 4′6-diamidino-2-phenylindole (DAPI) fluorescence. Optimal uptake occurred after 10 min of electrophoresis at 10 volts and 0.5 milliamps. Under these conditions, 55% of the embryos survived the treatment and 57% of those which survived were transformed as measured by GUS-positive staining. Leaves from 6 month old plants which developed from the transformed embryos expressed specific patterns of GUS staining.

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R. J. Griesbach

Genetic complementation was used to correct the albescent flower color mutation of the orchid Doritis pulcherrima. The Zea mays anthocyanin regulatory genes C 1 and B were introduced into the petal cells via particle bombardment. Anthocyanin pigmentation developed within the bombarded cells after 48 hours. This suggests that the albescent phenotype was the result of a defective regulatory gene(s) and not the result of a defective structural gene(s). Genetic complementation via particle bombardment requires considerably less time than via classical breeding and could be used on other species or with other genes.

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R.J. Griesbach

The environment can affect the intensity of flower color in Eustoma grandiflorum. Low light and alkaline pH within the growing cell can lead to reduced color intensity. Two independent causes are responsible for the decrease in the intensity of flower color. 1) Older flowers were more alkaline than freshly opened flowers. A 7% increase in pH was related with a 10% reduction in color intensity. 2) Flowers that open under low light were paler than those opening under high light intensity. A 25% decrease in light intensity was related to a 30% reduction in the concentration of anthocyanin and a 40% reduction in color intensity.

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R.J. Griesbach

The biochemistry of flowers is very complex, depending not only on the specific anthocyanin present but also on vacuolar pH, presence of metal ions, type of co-pigment present, and the molar ratio of co-pigment to anthocyanin. Because of the wide array of different flower colors, Petunia hybrida is an excellent model system to study the genetic interaction of all of these factors. The segregation of the different flower colors in an F2 population from a red × violet outcross could be explained through the combined inheritance of anthocyanin pigmentation and pH. The inheritance of anthocyanin pigmentation was controlled by two independent genes (hf and Mf) that followed simple Mendelian genetics. The inheritance of pH was more complex, being controlled by two independent co-dominant genes (Ph1 and Ph2). Linkage of the various pH and anthocyanin genes prevented the expression of all of the potential gene combinations.

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R.J. Griesbach

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R.J. Griesbach

A regulatory gene, An2, controls structural genes within the flavonoid biosynthetic pathway. The inheritance of An2 expression in crosses between P. axillaris (an2) and P. exserta (An2+) was studied. Floral pigmentation was quantitatively inherited and involved the expression of a single regulatory gene (An2) and three structural genes (Hf1, An6 and Fl). White flowers were produced in an2- genotypes; while pigmented flowers were produced in An2+ genotypes. The intensity of pigmentation was determined by the interaction of An2 with An6, Hf1 and Fl, as well as substrate competition between the An6 and Fl encoded enzymes.

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R.J. Griesbach

An in vivo system was developed to determine the effects of pH on naturally occurring pigment complexes within cells. The in vivo system was based on a transposable element activator (Ac) inserted into the Ph6 gene. The transposable element activator (Ac) was crossed into two genetically marked Petunia hybrida lines expressing known flavonoid pigments. Plants expressing the transposable element activator (Ac) produced variegated flowers in which the background tissue was lighter in intensity than the sectors. Depending on the genetic background in which the transposable element is expressed, progeny with darker sectors that were also redder in color than the background tissue could also be obtained. The anthocyanin and copigment composition was the same for both of the differently colored sectors and background tissue, while the pH was lower by 0.4 unit in the redder sectors. It was suggested that the Ph6 gene might be a regulatory gene that controls the expression of the pH and anthocyanin concentration.