Progress 10/01/04 to 09/30/09
OUTPUTS: Premature flower wilting reduces the vase life and quality of cut flowers and potted plants. The purpose of this study was to learn more about the way plants regulate senescence of their flowers to that we can delay flower wilting. Specifically, our objectives were: to develop and utilize the VIGS system in Petunia for functional analysis of genes associated with flower senescence, to examine the temporal and spatial/temporal expression of unknown and putative regulatory genes whose abundance increases during petal senescence, to test the effects of down-regulation of selected senescence-associated genes on petal senescence, using VIGS in Petunia, and to confirm the effects observed using VIGS in stably-transformed Petunia plants. Our approach to achieving these objectives was to use Virus Induced Gene Silencing to silence putative regulatory genes, and genes of unknown function that have been shown to be up-regulated during floral senescence in Petunia. Where silencing of a gene caused a change in the onset or progression of senescence, we targeted that gene for further investigation, including stable transformation in sense and anti-sense, to provide further information as to its role in senescence. In the later stages of the project we examined the use of an inducible transgenic approach, where gene constructs that we suspected would delay senescence could be induced with a benign chemical during the postharvest period. In addition to the research and graduate student instruction associated with it, I have been involved in a range of educational activities, in particular the PRO institutes and advanced PRO institutes in which I work with a colleague in the private sector to provide current information on postharvest floriculture to leaders from the production, shipping, wholesale, and retail sectors of the floricultural industry. The annual UCDavis postharvest short course, in which I participate ,is also an significant educational event, providing postharvest information to more than 100 members of industry and academia through a week of classroom lectures, and a week field trip visiting postharvest facilities throughout California. As well as the new and fundamental knowledge exemplified by the publications below, products from the program include the licensing of thidiazuron (TDZ) as a tool for extending the life of cut flowers by preventing leaf yellowing. We have now also demonstrated the spectacular efficacy of this material in extending the life of a range of potted plants and anticipate licensing this application as well. Four Ph.D. students completed their studies during the project. PARTICIPANTS: Individuals working on the project: In addition to the PI, graduate students Xinjia Chu, Genevieve Stier, and Yin-Chih Liang worked on the project. A postdoctoral fellow, Andrew MacNish was also involved, and the project involved close collaboration with an ARS scientist, Cai-Zhong Jiang. Partner organizations, collaborators, and contacts George Staby, of the Perishables Research Organization collaborated in some of the outreach activities, and numerous visiting scholars and colleagues from around the world were contacted in the course of the project. Training and Professional Development The PRO institutes described above, and the annual postharvest short course and ripening workshop are outreach activities that were undertaken to reach growers, shippers, and marketers for the purpose of advancing their knowledge of postharvest science and technology and encouraging improved postharvest handling and reducing postharvest food losses. As a member of the UCD postharvest research and outreach information center, I contribute to the highly regarded (and heavily trafficked) postharvest website (http://postharvest.ucdavis.edu) and monthly electronic newsletter. In addition I provide occasional contributions to the California Ornamentals Research Federation newsletter - a publication for ornamental growers and shippers from California. TARGET AUDIENCES: The target audiences for this project were fellow scientists, cut flower and potted plant producers, shippers, and marketers, and agrichemical and breeding companies that would potentially use the results of the research. PROJECT MODIFICATIONS: Not relevant to this project.
The outcomes of this project include information that is already being used by industry to improve the life of cut flowers, particularly the use of TDZ to increase the life of cut flowers and potted plants In addition, the project has provided fundamental information on the role of structural and regulatory genes in flower senescence. The results of experiments using silencing of a 26S proteasome subunit to extend flower life have been submitted for patenting, and potential licensees are presently being sought. Likewise a major agrichemical company has expressed interest in licensing the use of TDZ to extend the life of potted plants. Our research into the regulation of abscission has clarified the role of different cell wall enzymes in the process, and points the way to transgenic strategies to reduce postharvest petal and leaf loss.
- Macnish, A.J., C-Z Jiang and M.S. Reid. (2010). Treatment with thidiazuron improves opening and vase life of iris flowers. Postharvest Biology & Technology 56: 77-84.
- Macnish, AJ, A deTheije, MS Reid and C-Z Jiang. (2009) An alternative postharvest handling strategy for cut flowers - dry handling after harvest. Acta Hort. 847:215-221.
- Macnish, AJ, C-Z Jiang and MS Reid. (2009) Nicotiana mutabilis - a novel system for studying ethylene-mediated floral senescence. Acta Hort. 847:95-102.
- Jiang, C-Z, L.Wu, AJ Macnish, A King, M Yi and MS Reid. (2009) Thidiazuron, a non-metabolized cytokinin, shows promise in extending the life of potted plants. Acta Hort. 847:59-65.
- Reid, MS, J.C. Chen and C-Z Jiang (2009) Virus-Induced Gene Silencing for Functional Characterization of Genes in Petunia. In Petunia: Evolutionary, Developmental and Physiological Genetics. T. Gerats ed. Springer, New York, pp381-394.
Progress 01/01/08 to 12/31/08
OUTPUTS: Premature flower wilting reduces the vase life and quality of cut flowers and potted plants. The purpose of this study is to learn more about the way plants regulate senescence of their flowers to that we can delay flower wilting. Specifically, our objectives are: to develop and utilize the VIGS system in Petunia for functional analysis of genes associated with flower senescence, to examine the temporal and spatial/temporal expression of unknown and putative regulatory genes whose abundance increases during petal senescence, to test the effects of down-regulation of selected senescence-associated genes on petal senescence, using VIGS in Petunia, and to confirm the effects observed using VIGS in stably-transformed Petunia plants. Our approach to achieving these objectives is to use Virus Induced Gene Silencing to silence putative regulatory genes, and genes of unknown function that have been shown to be up-regulated during floral senescence in Petunia. Where silencing of a gene causes a change in the onset or progression of senescence, we plan to target that gene for further investigation, including stable transformation in sense and anti-sense, to provide further information as to its role in senescence. PARTICIPANTS: Not relevant to this project. TARGET AUDIENCES: Not relevant to this project. PROJECT MODIFICATIONS: Not relevant to this project.
During the last year we have been refining techniques for the use of Virus-induced gene silencing (VIGS), a powerful tool for examining the effects of silencing individual genes so that we can understand their function. We determined that our inability to implement VIGS in a wide range of species was partly due to the need for highly specific silencing fragments, and we have developed a set of universal primers that enable us to isolate fragments of the phytoene desaturase gene from many plant species. In implementing VIGS we need a reporter gene, and in floral senescence studies we have used chalcone synthase. Silencing this gene in flowers whose petals are normally purple results in white petals, a change that makes an excellent reporter for the location of silencing events. For studies in vegetative or non-purple tissues, we decided to test the use of transgenic plants expressing green fluorescent protein (GFP). These plants fluoresce bright green when exposed to long-wavelength UV light. Infection with virus containing a fragment of the GFP sequence resulted in silencing, and loss of the green fluorescence, which makes this another very useful reporter gene. Events: In addition to the research and graduate student instruction associated with it, we continue to participate in a range of educational activities, including the PRO institutes in which I work with a colleague in the private sector to provide current information on postharvest floriculture to leaders from the production, shipping, wholesale, and retail sectors of the floricultural industry. In the last year we also held an advanced PRO institute for a smaller number of industry leaders, who participated in laboratory experiments and demonstrations. The annual UCDavis postharvest short course, in which I participate, is also a significant educational event, providing postharvest information to more than 100 members of industry and academia through a week of classroom lectures, and a week field trip visiting postharvest facilities throughout California. In addition to the new and fundamental knowledge exemplified by the publications below, products from the program include the licensing of thidiazuron (TDZ) as a tool for extending the life of cut flowers by preventing leaf yellowing. We have further demonstrated that this material can increase flower opening and extend longevity of a number of flowers; the treatment is extremely effective with iris and bird of paradise. We have also demonstrated that a common oxidizing chemical can be used to greatly reduce the severity of postharvest infection of roses with Botrytis, and are testing its efficacy in other susceptible flower species.
- Reid, M. S. and G. L. Staby. 2008. A brief history of 1-methylcyclopropene. Hortscience 43(1):83-85.
- Reid, M.S. and F.G. Celikel. 2008. Use of 1-methylcyclopropene in ornamentals: carnations as a model system for understanding mode of action. Hortscience 43(1):95-98.
- Jiang, C.Z., Lu, F., Imsabai, W., Meir, S., and Reid, M.S. 2008. Silencing polygalacturonase expression inhibits tomato petiole abscission. J Exp Bot. 59(4):973-9.
Progress 01/01/07 to 12/31/07
Activities: During the last year, I have continued to conduct and analyze experiments designed to understand the function of genes associated with the regulation of flower senescenceVirus-induced gene silencing was used to study the role of cell wall modifying enzymes and proteins on petal and leaf abscission. We have also determined the effect of commercial plant growth regulators on the postharvest performance of potted plants. Events: In addition to the research and graduate student instruction associated with it, I have been involved in a range of educational activities, in particular the PRO institutes in which I work with a colleague in the private sector to provide current information on postharvest floriculture to leaders from the production, shipping, wholesale, and retail sectors of the floricultural industry. The annual UCDavis postharvest short course, in which I participate, is also a significant educational event, providing postharvest information to more
than 100 members of industry and academia through a week of classroom lectures, and a week field trip visiting postharvest facilities throughout California. Products: In addition to the new and fundamental knowledge exemplified by the publications below, products from the program include the licensing of thidiazuron (TDZ) as a tool for extending the life of cut flowers by preventing leaf yellowing. We have now also demonstrated the spectacular efficacy of this material in extending the life of a range of potted plants and anticipate licensing this application as well. Two Ph.D. students completed their studies during the year. Dissemination: The PRO institutes described above under events, and the annual postharvest short course and ripening workshop are outreach activities that were undertaken to reach growers, shippers, and marketers for the purpose of advancing their knowledge of postharvest science and technology and encouraging improved postharvest handling and reducing
postharvest food losses. As a member of the UCD postharvest research and outreach information center, I contribute to the highly regarded (and heavily trafficked) postharvest website (http://postharvest.ucdavis.edu) and monthly electronic newsletter. In addition I provide occasional contributions to the California Ornamentals Research Federation newsletter - a publication for ornamental growers and shippers from California.
We have demonstrated the effects on floral senescence of silencing a gene that encodes an ubiquitin ligase - part of the regulatory mechanism that targets proteins for destruction. Using Virus-Induced gene silencing in Petunia, we demonstrated that silencing this gene resulted in an increased longevity of the corolla. We also showed that silencing TAPG1, a polygalacturonase, significantly delayed abscission, whereas silencing endoglucanases (cellulases) and expansins had no obvious effect. Working with growers, we have demonstrated that flowers are not improved by being placed in water immediately after harvest, and may, in fact, perform better when handled dry from harvest to wholesale. We have demonstrated the usefulness of Radio Frequency Identification Tags equipped with batteries to allow continuous monitoring of temperature and other environmental parameters in monitoring temperature conditions during the transportation of cut flowers.
- Xu, X., Jiang, C-Z, Donnelly, L., and Reid, M.S. 2007. Functional analysis of a RING domain ankyrin repeat protein that is highly expressed during flower senescence J. Exp. Bot. 58: 3623-3630.
- Reid, M., and Chen, J-C., 2007. Flower senescence, In (Su-Sheng Gan, Ed.,) Senescence Processes in Plants, Blackwell.
- Reid, M. and Staby, G., 2007. Active RFID tags - a new tool for improving temperature management during the marketing of cut flowers. CORF News 11(1):1, 2, 11.
- Reid, M., Macnish, A., and De Theije, A., 2007. Removing buckets from the postharvest chain. CORF News 11(1):1, 5.
Progress 01/01/06 to 12/31/06
Our group has continued exploration of the function of genes associated with the processes of senescence and abscission in cut flowers and potted plants. In the last year we have isolated and characterized the expression of a number of genes associated with flower senescence in Mirabilis jalapa, our chosen model system, including a RING zinc finger protein which has high homology to ubiquitin ligases in other species. Abundance of transcripts of this gene increases 40,000 fold during the onset of corolla senescence. We have isolated the promoter of this gene, and determined the activity of different portions of the promoter, using promoter fragments fused to GUS. A 1kb fragment is sufficient to drive maximal GUS expression during petal senescence. The gene has highly homologous counterparts in other species that we have examined, and the promoter/GUS fusion is able to drive GUS expression in other species, including petunia and carnation. The promoter activity appears
to be highly specific to floral tissues and floral senescence, but this remains to be confirmed by more in-depth analysis. Curiously, the promoter does not drive expression in petals of senescing monocotyledonous flowers, whether they are ethylene sensitive or insensitive. The promoter contains numerous domains characteristic for binding of a range of transcription factors, and it appears possible that this ubiquitin ligase plays a key role in regulating the onset of floral senescence.
Rapid floral senescence is a characteristic of many beautiful commercial cut flowers like iris, and of an even larger number of showy blooms whose life is too short to enable them to be commercialized. Our research is developing the fundamental knowledge that will allow us to engineer longer-lasting cultivars of such flowers, thereby increasing the palette of species available to commercial and amateur horticulturists for use as potted plants or cut flowers.
- Stewart, B.A, Reid, M.S., Ransom, N.A., and Slack, D.C. 2005 Impact of climate change on water supply and agriculture - Crop/Water management guidelines and extension dissemination. Science and Culture 71:288-292.
- Meir S, Hunter D.A., Chen J.C., Halaly V., Reid M.S. 2006 Molecular changes occurring during acquisition of abscission competence following auxin depletion in Mirabilis jalapa. Plant Physiol. 141:1604-1616.
- Reid, M.S. Air transport of cut flowers. 2006 In:Perishable Cargo Manual, 6th Edition, International Air Transport Association, pp. 175-186.
Progress 01/01/05 to 12/31/05
During the period under review we continued our work using Virus-induced gene silencing (VIGS) to test the function of genes that we have found to be associated with flower senescence. Of particular interest was a gene encoding a protein called prohibitin. This protein has been intensively studied in humans because it was found that a mutation in the gene encoding it was associated with uncontrolled cell division in mammary cancer. Studies in yeast have demonstrated that it is a mitochondrial protein with two isoforms that polymerize to form a mega-complex in the mitochondrial membrane that is critical for proper assembly and maintenance of the proteins comprising the respiratory chain. Mutations in the prohibitn gene cause abnormal mitochondrial structure and function. In plants, genes that have high homology to animal and yeast prohibitins have been identified in Arabidopsis, maize, rice, and tobacco. Attempts to determine the function of these plant prohibitins
have been unsuccessful, apparently because silencing or over-expression of this protein is lethal in young plants. We used VIGS to silence prohibitin1 in Petunia, and obtained phenotypes that are consistent with a similar function, in plants, to that already observed in animals and yeast. Flowers of silenced plants were smaller than controls, yet the petal cells were considerably larger. We interpret this to indicate a negative effect of silencing prohibitins on cell division during petal development. Petals of silenced flowers had a higher respiration rate, wilted earlier, and contained more abundant transcripts of catalase, an enzyme involved in detoxification of reactive oxygen species (ROS). As in yeast and human systems, therefore, we feel that we have established a case that plant prohibitins are involved in mitochondrial structre and function. As part of our project, we have been isolating genes that are up- and down- regulated during petal senescence. Using the four oclock
flower (Miorabilis jalapa) as a model system, we have demonstrated changes in a large number of independent genes. In some cases, there were very large changes (for example a 30,000 fold increase in transcript abundance of a ring zinc finger protein), and we have been isolating promoters from genes showing these dramatic changes at the onset of senescence. Our intent is to test a strategy where these promoters are used to turn on synthesis of a protein that will interfere with protein synthesis and thereby prevent the synthesis of the enzymes responsible for petal senescence.
The per-capita consumption of cut flowers in the U.S. is much less than that in other first-world countries, less than a quarter, for example of that in Britain. This is directly attributable to consumer dissatisfaction with the low vase life of flowers as they are presently marketed. Focusing on increasing vase life of flowers in supermarkets (the major outlet for fresh cut flowers) will increase consumption, and thereby improve profitability for farmers and traders. Our outreach activities already have increased the focus of the industry in improving freshness, and we have set a goal of doubling cut flower consumption in five years, a target that mirrors the recent increases in consumption in Britain, also driven by improving (and guaranteeing) flower freshness.
- Jiang, C.Z., Chen, J.C., and Reid, M.S. 2005. Functional analysis of genes associated with flower senescence. Acta Hort. 682: 795-800
- Reid, M.S., and Jiang, C-Z. 2005. New strategies in transportation for floricultural crops. Acta Hort. 682:1667-1673.
- Celikel, F.G., and Reid, M.S. 2005. Temperature and postharvest performance of rose (Rosa hybrida L. First Red) and gypsophila (Gypsophilapaniculata L. Bristol Fairy). Acta Hort. 682. 1789-1794. Chen, J.C., Johnson, F., Clark, D.G., Gookin, T., and Reid, M.S. 2005. Potential application of virus-induced gene silencing (VIGS) in flower senescence studies. Acta Hort. 669:147-152
- Reid, M.S. 2005. An efficient regeneration system for Four Oclocks (Mirabilis jalapa). Acta Hort. 669:153-156.
- Reid, M.S. 2005. Trends in flower marketing and postharvest handling in the United States. Acta Hort. 669:29-33.
- Reid, M.S. 2005. Flower development: From bud to bloom. Acta Hort. 669:105-109.
- Chen, J-C. Jiang, C-J, and Reid, M.S. 2005. Silencing a prohibitin alters plant development and senescence. Plant J. 44:16-24.
Progress 01/01/04 to 12/31/04
During this year we have started to analyse the function of the many genes that we and others have isolated from different systems and that appear to be associated with floral senescence. Our primary tool in this analysis is the use of Virus-Induced gene silencing. We are using a unique approach in which the Tobacco Rattle Virus (TRV) genome is engineered to contain petunia chalcone synthase (CHS) and a gene of interest. When purple-flowered petunia plants are infected with this engineered virus, the plants virus silencing system turns off its own chalcone synthase gene (because it's included in the infecting virus) and the infected flowers (or sectors of the flowers) are white, because CHS is required for the synthesis of the purple anthocyanin pigments. The white sectors serve as a 'reporter' showing where gene silencing is occurring and we can examine the effects of silencing our unknown gene on the senescence of the flowers. To date we have examined the function
of more than 50 genes whose expression appears to be altered during floral senescence. In some cases these genes have no effect on floral longevity, but silencing some of our candidate genes has shortened life of the flowers (suggesting that they are involved in retaining petal function), and silencing others has increased flower life (suggesting that they may be involved in floral senescence).
The fundamental information that we are obtaining will be very useful to breeders seeking to develop longer-lasting flowers. Many beautiful flowers, including commercial crops, such as Dutch iris, have an unacceptably short vase life, and the rigors of the marketing chain result in losses that are estimated at up to 25% of the harvested flowers. Poor performance of flowers in the home is a root cause for recent lackluster sales of ornamentals in the U.S., and we feel that improving postharvest performance will not only reduce direct losses, but also encourage repeat sales, and increased consumption. The genes that we are identifying may be the key to providing new floricultural crops with genetically improved vase life.
- Chen, J.C., Jiang, C.Z., Gookin, T.E., Hunter, D.A, Clark, D.G. and Reid, M.S. 2004. Chalcone synthase as a reporter in virus-induced gene silencing studies of flower senescence. Plant Molecular Biology. In Press. Hunter, D.A., Lange, N. and Reid, M.S. 2004. Physiology of Flower Senescence. In [Nooden, L., Ed.] Cell Death in Plants. Elsevier Science, USA. pp. 307-319.
- Hunter, D.A., M.F. Yi, X. Xu and M.S. Reid. 2004. Role of ethylene in perianth senescence of Daffodil (Narcissus pseudonarcissus L. 'Dutch Master'). Postharvest Biology & Technology 32:269-280.
- Hunter, D.A., A. Ferrante and M.S. Reid. 2003. Role of abscisic acid in perianth senescence of daffodils (Narcissus pseudonarcissus 'Dutch Master'). Physiologia Plantarum, 121:313-321.
- Ferrante, A., D.A. Hunter and M.S. Reid. 2003. Towards a molecular strategy for improving harvesting of olives (Olea europaea L.). Postharvest Biology & Technology. Postharvest Biology & Technology 31:111-117.
Progress 01/01/03 to 12/31/03
Although we are continuing to test a range of strategies (including novel selectable markers) for stable transformation of four o'clocks, our model system for ethylene-independent floral senescence, we have focused considerable effort in the past year on the use of Virus-induced gene silencing as a strategy for testing the function of target genes in species that are recalcitrant to transformation. Initial studies have used petunia as a model system because of its well-studied senescence patterns and its close relationship to Nicotiana, the genus in which the current generation of gene-silencing vectors has been developed. Petunias are infected with tandem constructs where the RNA2 of tobacco rattle virus (TRV) is modified by insertion of chalcone synthase and the target gene. Where virus infection occurs, the plant's silencing mechanism also silences chalcone synthase (a key enzyme in anthocyanin biosynthesis), resulting in white sectors on the otherwise purple
flowers. The effect of the test gene on flower senescence can be determined by comparing the pattern of senescence in the purple and white sectors in individual flowers. Since it is likely that the senescence process is coordinated through control elements such as transcription factors, kinases, and DNA binding factors our studies have focused on transcription factors identified in a large EST database housed at the University of Florida. The results of VIGS silencing of selected transcription factors on flower senescence will be reported. Future studies will extend this technology to flowers where ethylene is not involved in the coordination of flower senescence.
Our previous work has identified tools for preventing floral senescence in ethylene-sensitive flowers. In the current period we have also demonstrated that daffodils, previously considered ethylene-insensitive, do in fact respond to exogenous ethylene. In the future, the life of daffodil flowers handled through mass markets will be substantially improved by pre-treating them with inhibitors of ethylene action such as 1-methyl-cyclopropene. The North American market for cut flowers, presently about $1 billion, represents a consumption per capita of $3. This is similar to that in Russia, 1/15th of that in the U.K., and 1/30th of that in Switzerland. The potential for increasing the market depends on providing consumers with longer-lasting flowers, the primary goal of our project.
- GOOKIN, T.E., HUNTER, D.A. and REID, M.S. 200.3 Temporal analysis of alpha and beta-expansin expression during floral opening and senescence. Plant Science 164:769-781.
- REID, M.S. 2003. Postharvest handling, packing systems and precooling. Encyclopedia of Rose Science.
- Reid, M.S. 2003. Postharvest Physiology Effects of Temperature. Encyclopedia of Rose Science.
- HUNTER, D.A., LANGE, N. and REID, M.S. 2003. Physiology of Flower Senescence. In (Nooden, L., Ed.) Cell Death in Plants. Academic Press. 307-319.
Progress 01/01/02 to 12/31/02
We are developing the tools that we need to test the function of the wide range of genes that have been isolated from senescing flowers of daffodil and four o'clock, our present model systems. After considerable effort, we finally have a successful system for regeneration of four o'clocks, using cotyledons from mature seeds as our explant. Presently we are testing a range of strategies for transformation of these explants with a test construct bearing the green fluorescent protein reporter gene. We anticipate rapid progress with the four o'clock system, which has the advantage of a rapid generation time (seed to seed in 8 to 10 weeks) and a rapidly senescing ethylene-independent flower. Daffodils, in contrast, cannot easily be transformed and regenerated, and the time taken to see floral phenotypes from a successful transformation may be as much as 3 years. Accordingly, we are testing various strategies for transient examination of the function of
senescence-associated genes, including Virus Induced Gene Silencing, and other RNAi techniques.
of commercial flowers, and beautiful wildflowers that would be appropriate in commerce if they had a longer vase life. In the world market for cut flowers, estimated at $9 billion, flowers with ethylene-independent senescence pathways probably account for at least 30% of the products sold. Losses of floral products due to early senescence are estimated at 20%, so the potential economic impact of this work is substantial.
- CELIKEL, F.G., DODGE, L.L. and REID, M.S. 2002. Efficacy of 1-MCP (1-methylcyclopropene) and promalin for extending the post-harvest life of Oriental lilies (LILIUM x `Mona Lisa' and `Stargazer'). Scientia Horticulturae 93(2):149-155.
- REID, M.S. 2002. Maturation and maturity indices. IN: Postharvest Technology of Horticultural Crops, 3rd edition. Adel Kader, Technical Editor. University of California, Agriculture and Natural Resources, Publication 3311, pp. 55-62.
- REID, M.S. 2002. Postharvest handling systems: ornamental crops. IN: Postharvest Technology of Horticultural Crops, 3rd edition. Adel Kader, Technical Editor. University of California, Agriculture and Natural Resources, Publication 3311, pp. 315-325.
- CELIKEL, F.G. and REID, M.S. 2002. Storage temperature affects the quality of cut flowers from the Asteracease. HortScience 37:(1):148-150.
- CELIKEL, F.G. and REID, M.S. 2002. Postharvest handling of stock (MATTHIOLA INCANA). HortScience 37:(1):144-147.
- FERRANTE, A., HUNTER, D.A., HACKETT, W.P. 2002. Thidiazuron - a potent inhibitor of leaf senescence in ALSTROEMERIA. Postharvest Biology and Technology 25:333-338.
- HUNTER, D.A., STEELE, B.C. and REID, M.S. 2002. Identification of genes associated with perianth senescence in Daffodil (NARCISSUS PSEUDONARCISSUS L. `Dutch Master'). Plant Science 163:13-21.
- REID, M.S., WOLLENWEBER, B. and SEREK, M. 2002. Carbon balance and ethylene in the postharvest life of flowering hibiscus. Postharvest Biology and Technology 25:227-233.
- REID, M.S., FERRANTE, A., HUNTER, D.A. and HACKETT, W.P. 2002. Compositions and methods for preventing leaf yellow in plants. UC Case No. 2000-492-1, United States Patent No. 6,455,466. September 24, 2002.
Progress 01/01/01 to 12/31/01
﻿This year we have focused on gene discovery and understanding the role of specific genes in floral development and senescence. Our model system, MIRABILIS JALAPA, has proven to be a very useful tool, and we have identified a family of alpha-expansin transcripts (MjExp1 through MjExp6) and an expansin-like transcript (MjExpL1) that show dynamic changes in abundance during the rapid expansion and subsequent enescence of these ephemeral flowers. In general, alpha-expansin transcript abundance was low or undetectable in small buds, peaked during maximal elongation of the floral tube, declined to low levels during floral display and, for some members of the family, increased during the in-folding and collapse of the corolla.
﻿The losses of floral crops after harvest are estimated to be in the range of 25%. Our research has provided tools to reduce the negative effects of ethylene, to improve temperature management so as to slow deterioration, and to overcome the premature senescence of leaves. The impact of our molecular work will be very substantial, if we can develop strategies for enhancing the life of ephemeral flowers such as daffodil and iris, whose corolla senescence is not regulated by ethylene.
- Cho, M.S., Celikel, F., Dodge, L.L. and Reid, M.S. 2001. Sucrose enhances the postharvest quality of cut flowers of Eustoma Grandiflorum (Raf.) Shinn. Acta Hort. 453:305-315.
- Reid, M.S. and Hunter, D.H. Manejo de la poscosecha. 2000. IN Clavel (M. Pizano deMarquez, Ed). HortiTechnia Ltda, Colombia, pp. 165-181.
- Cevallos, J.C. and Reid, M.S. 2001. Effect of dry and wet storage at different temperatures on the vase life of cut flowers. HortTechnology 11(2)199-202.
- Cameron, A.C. and Reid, M.S. 2001. 1-MCP blocks ethylene induced petal abscission of Perlargonium peltatum but the effect is transient. Postharvest Biology and Technology 22:169-177.
- Waithaka, K., Dodge, L.L. and Reid, M.S. 2001. Carbohydrate traffic during opening of gladiolus florets. J. Hort. Sci. & Biotech. 76(1)120-124.
- Waithaka, K., Reid, M.S.and Dodge, L.L. 2001. Cold storage and flower keeping quality of cut tuberose (Polianthes tuberose L.). J. Hort. Sci. & Biotech. 76(3)271-275.
- Hunter, D.H. and Reid, M.S. 2001. A simple and rapid method for isolating high quality RNA from flower petals. Acta Hort. 453:147-152.
- Waithaka, K., Dodge, L.L. and Reid, M.S. 2001. Carbohydrate traffic during opening of gladiolus florets. Acta Hort. 453:217-226.
- Reid, M.S. 2001. Advances in shipping and handling of ornamentals. Acta Hort. 453:277-284.
Progress 01/01/00 to 12/31/00
Our studies in the period under review have included a range of approaches to understanding the molecular biology and physiology of senescence in ephemeral flowers. Using daffodil as our initial model system, we demonstrated that although ethylene is not an important endogenous regulator of senescence, the flowers senesce more rapidly in the presence of this common air pollutant. Pre-treatment with 1-MCP will therefore improve the life of daffodils and other species of Narcissus used in commercial floriculture. From daffodil we isolated a large number of cDNA clones that are strongly up-regulated prior to or during the onset of senescence, including cysteine proteases, a subtilisin, and a range of other intuitive species. Because daffodil is not readily amenable to transformation and regeneration, our studies have continued with MIRABILIS JALAPA, the four o'clock. The flowers of this dicotyledonous plant last a scant 16 hours, opening in the evening, and wilting the
next morning. The physiology of four o'clock floral senescence mirrors that of daffodil, and we have already isolated a range of cDNAs that are upregulated during floral opening and senescence. Efforts to transform and regenerate this short cycling species are under way and appear promising.
Increasing the longevity of cut flowers and potted plants is an important factor in improving the profitability and expanding the market for these products in the U.S. 1-MCP is now being used commercially, not just for the traditionally ethylene-sensitive crops such as carnations and larkspur, but for a range of crops where we have shown benefits, including daffodil and roses. The reduction in postharvest losses is quite apparent, and this treatment is now being used routinely in truck shipments from California and Florida to all parts of the continental U.S.
- Reid, M.S. and M. Serek. 2000. Growth regulators and the postharvest life of ornamentals. In (Basra, A., Ed.). Growth Regulators in Horticulture.
- Macnish, A.J., D.C. Joyce, P.J. Hofman, D.H. Simons and M.S. Reid. 2000. 1- Methylcyclopropene treatment efficacy in preventing ethylene perception in banana fruit and grevillea and waxflower flowers. Australian Journal of Experimental Agriculture 40:471-481.
- Serek, M. and M.S. Reid. 2000. Ethylene and postharvest performance of potted kalanchoe. Postharvest Biology and Technology 18:43-48.
- Reid, M.S. and D.A. Hunter. 2000. Postcosecha. In (Pizano, M. Ed.) LaClavel. Asocoflores, Colombia.