2008 Annual Report
1a.Objectives (from AD-416)
1. Determine flower freshness during postharvest handling.
2. Development of a freshness index.
3. Identification and characterization of senescence-associated genes/promoters: a) Isolation of gene specific promoters; b) Targeted regulation of senescence-associated genes; c) Targeted inihibition of protein synthesis.
1b.Approach (from AD-416)
1) Freshly cut flowers of different species (at least two cultivars for each species) will held at different temperatures, and their respiration rate will be determined.
2) From a pre-existing database of genes whose expression changes during petal senscence in daylily, four o'clocks, and daffodils, as well as published databases on iris, carnation, and petunia we will identify genes whose expression pattern suggests an association with senescence.
3a) Using EST collections we will identify genes whose expression changes dramatically in the early stages of floral senescence.
3b) Transgenic petunia plants will be generated using standard techniques, and the life of the flowers from the transformed plants will be compared with that of control plants.
3c) Transform petunia with constructs combining floral senesence-specific promoters with genes encoding proteins known to interfere with ribosome function. Documents SCA with UC Davis.
The ornamental industry faces postharvest challenges-ethylene-induced flower senescence, losses due to disease, & lack of germplasm with desirable postharvest traits. We are developing technological, chemical, & molecular strategies to address these issues. PROGESS:1)Silencing protein synthesis or degradation as a tool for delaying floral senescence-We hypothesize that targeted inhibition of protein synthesis or degradation at the onset of senescence could extend flower life. Virus induced gene silencing was used to test effects of silencing protein synthesis or protein degradation. The id of effective targets for the inhibition of protein synthesis & targeted protein degradation paves the way for further research into the mechanisms & control of floral senescence. 2)Develop tools for testing flower freshness-The goal was to identify a common set of genes for use as freshness indicators in cut flower species. Expression of a gene encoding a putative nuclease increased greatly during the final stages of flower development & aging. This protein may play an important role in the regulation of floral senescence in a wide range of species & is a promising candidate for a universal marker to predict flower freshness. 3)Nicotiana mutabilis mediated floral senescence-Nicotiana mutabilis, a tobacco species, has flowers that change color during their display life. Opening buds are white, and as the flower ages, the color changes to light pink, then dark pink & finally red. The onset of pigment change is associated with a marked increase in ethylene production, and the change is retarded by treating with an inhibitor of ethylene action. Expression of the genes encoding chalcone synthase & a senescence-associated gene increased substantially as petal anthocyanins increased. The numerous genetic & experimental tools available for N. tabacum can be applied to this close relative, and provide a new model for studying flower senescence. 4)Alternative chemical control methods for Botrytis cinerea infection of rose-Botrytis infection is a major postharvest disease. We explored the use of novel chemicals as postharvest dip treatments on susceptible varieties of Rosa hybrida. Our data demonstrated that the fungicide ‘Palladium’ was effective in preventing infection of cut roses when applied as a postharvest dip at very low concentrations. Oxidizing chemicals such as H2O2 & sodium benzoate may offer a safer alternative. We continue to explore alternative treatments using similar chemicals. 5)Effect of temperature on quality & display life of potted plants-We tested the effect of storage temperature on the quality & display life of Campanula plants. Low temperatures during storage nearly doubled the # of fresh flowers & buds, and more than halved the number of aborted buds on plants after 1 week in the postharvest evaluation. The ADODR monitors this SCA by maintaining a complete file of the agreement, reviewing annual reports, & meeting with the cooperator.