Search Results

You are looking at 1 - 10 of 21 items for

  • Author or Editor: Robert J. Griesbach x
Clear All Modify Search
Free access

Robert J. Griesbach

Flower color results from the interaction of a pigment (anthocyanin) with a co-pigment (usually a flavonone or flavonol) at a specific pH. At more alkaline pHs (pH 5 to 6), an anthocyanin/co-pigment complex is blue; while at more acidic pHs (pH 3-4), the same anthocyanin/copigment complex is red. In Phalaenopsis pulcherrima, a mutation in pH resulted in a bluer flower color. The difference in pH between the normal-colored magenta flowers (pH 5.8) and mutant violet flowers (pH 5.5) was due to a single co-dominantly inherited gene.

Free access

Rosanna Freyre and Robert J. Griesbach

Plants of Anagallis monelli in their native habitat or in cultivation have either blue or orange flowers. Clonally propagated cultivars, seed obtained from commercial sources and the resulting plants were grown in a greenhouse at the University of New Hampshire. F2 progeny obtained from hybridization between blue- and orange-flowered plants had blue, orange or red flowers. There were no significant differences in petal pH of orange-, blue-, and red-flowered plants that could explain the differences in flower color. Anthocyanidins were characterized by high-performance liquid chromatography. Results indicated that blue color was due to malvidin, orange to pelargonidin, and red to delphinidin. Based on our segregation data, we propose a three-gene model to explain flower color inheritance in this species.

Restricted access

Mojdeh Bahar and Robert J. Griesbach

The U.S. Department of Agriculture’s Agricultural Research Service (ARS) and universities have a long and successful history of developing enhanced germplasm and cultivars that are transferred through public release. Today, nonprotected public release may not be the most appropriate mechanism. Intellectual property (IP) protection as it pertains to the plant germplasm and cultivars is involved and complex. Unlike other scientific areas, in the United States there are three distinct mechanisms to protect plants—namely, utility patents, plant patents, and plant variety protection certificates. Each of these mechanisms offers different criteria for protection and covers different types of plants. This article is a practical tool to help research institutions and scientists decide when to consider releasing a germplasm or cultivar, which factors to consider, who should be involved, and whether IP protection is appropriate.

Free access

John R. Stommel and Robert J. Griesbach

Ornamental peppers are a novel and growing segment of the ornamentals industry. Currently available varieties are utilized as pot plants and in bedding plant applications. Utilizing unimproved populations developed from initial crosses with Indian Capsicum land races, germplasm lines with unique gene combinations for multiple fruiting, fruit orientation, leaf pigmentation and leaf variegation were developed and released by USDA-ARS. Via introgression of diverse Capsicum species accessions and heirloom varieties into these populations, more recent efforts seek to exploit abundant genetic variation for fruit shape, size, color and pungency, foliar attributes, and plant growth habit to develop new pepper germplasm for ornamental and dual ornamental/culinary applications. Fruit pungency of selected material may range from mild to extremely pungent. Fruit shape may be round, conical, or lobed. Whereas small fruit size is generally well suited for ornamental applications, ornamental/culinary types exploit larger upright conical or small bell-shaped fruit. Plant foliage may be uniformly green in color, exhibit varying degrees of anthocyanin accumulation, or display variegation. Inheritance of selected attributes, potential barriers to development of select recombinants, and examples of representative advanced selections in the breeding program will be presented.

Free access

John R. Stommel and Robert J. Griesbach

Free access

John R. Stommel and Robert J. Griesbach

Free access

Rebeccah A. Waterworth and Robert J. Griesbach

Recently, several new Calibrachoa La Llave & Lexarza (Solanaceae Juss.) cultivars have been developed with novel red and blue flowers. Most wild species of Calibrachoa have purple flowers. The differences in color were not due to anthocyanin composition, but rather to vacuolar pH. The pH of the red-flowered cultivar was 4.8 while that of the blue-flowered cultivar was 5.6. The wild purple-flowered species had an intermediate pH of 5.0. These data suggest that different pH and pigment genes may be introgressed into other Calibrachoa species to increase cultivar diversity.

Free access

John R. Stommel* and Robert J. Griesbach

Anthocyanins contribute to color development in economically important vegetables, fruits and floral crops. Their expression is critical to product sensory quality attributes, potential nutritive value, and stress response. Anthocyanins are synthesized in response to numerous environmental factors including temperature and light stress and pathogen attack. We have developed several Capsicum lines, including `02C27', expressing anthocyanin pigmentation differentially in various tissues (leaf, stem, fruit and flower). HPLC analysis demonstrated that the anthocyanins within the fruit, flower and leaves of Capsicum `02C27' were identical and that the major anthocyanidin was a delphinidin glycoside. Line `02C27' exhibits anthocyanin foliar pigmentation that is accumulated differentially in response to temperature stress. Under unfavorable low temperature (20 °C day/18 °C night), mature Capsicum leaves contained 4.6 times less anthocyanin per gram fresh weight than under high (30 °C day/28 °C; day/night) temperatures. Besides containing less anthocyanin in mature leaves, young immature leaves did not develop color as quickly under the lower temperature. Utilizing cloned and sequenced gene fragments of pepper chalcone synthase (CHS), dihydroflavonol 4-reductase (DFR), and anthocyanidin synthase (ANS), we evaluated the role of transcription in regulation of flavonol biosynthesis. Analysis of anthocyanin composition and gene expression data indicated that the block in anthocyanin formation in less pigmented leaves occurred at anthocyanin synthase. In contrast to wild tupe plants, this mutant also exhibited reduced flowering and failed to set fruit under high temperature, long day conditions.

Free access

John R. Stommel and Robert J. Griesbach

Free access

John R. Stommel and Robert J. Griesbach

Considerable diversity exists in Capsicum L. germplasm for fruit and leaf shape, size, and color as well as plant habit. Using F1, F2, and backcross generations developed from diverse parental stocks, this report describes the inheritance patterns and relationships between unique foliar characters and diverse fruit and plant habit attributes. Our results demonstrate that pepper fruit color, shape, and fruit per cluster were simply inherited with modifying gene action. Broad-sense heritability for fruit color and shape and fruit per cluster was high, whereas narrow-sense heritability for these characters was moderate to low. Although fruit clustering was simply inherited, the number of fruit per cluster exhibited a quantitative mode of inheritance. High fruit counts per cluster were linked with red fruit color and anthocyanin pigmented foliage. Fruit shape was linked with immature fruit color and inherited independently of mature fruit color. Leaf color, length, and plant height were quantitatively inherited. Leaf shape did not vary, but leaf length varied and was positively correlated with leaf width. Broad-sense heritability for leaf characters, including leaf length, leaf width, and leaf color, was high. With the exception of leaf width, which exhibited low narrow-sense heritability, high narrow-sense heritability for leaf characters denoted additive gene action. Plant height displayed high broad-sense heritability. Moderate narrow-sense heritability suggested that additive effects also influence plant height. Analysis of segregating populations demonstrated that red and orange fruit color can be combined with all possible leaf colors from green to black. These results provide new data to clarify and extend available information on the inheritance of Capsicum fruit attributes and provide new information on the genetic control of leaf characters and plant habit.