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OPTOMIZE
Architectural engineering in the tomato

The greenhouse production of tomatoes is a key agricultural activity in several European countries. Although traditional breeding has produced high-yielding tomato varieties, several unresolved problems reduce efficiency. For example, side shoots have to be removed manually because they reduce yield from the main stem, and the non-uniformity of flowering results in non-uniform fruit development and quality. The consequences are increased labour costs, increased risk of disease and increased use of agrochemicals. Classical breeding will never be able to resolve all these issues. The OPTOMIZE project will optimise tomato plant architecture for greenhouse growth and, in parallel, will increase flavour and health benefits of fresh tomatoes by the targeted manipulation of key endogenous regulatory molecules controlling these processes. OPTOMIZE will therefore provide benefits to the grower by providing genotypes better adapted to the requirements of the greenhouse, and to the consumer who will be able to enjoy a tastier tomato with excellent health-promoting characteristics.

Objectives
For greenhouse-grown tomatoes, the key architectural problems that have to be resolved are:
1) the elimination of side shoots
2) the synchronisation of flowering
3) a fixed number of fruits per truss
4) optimised leaf shape and leaf number between trusses
5) uniform ripening
6) high-quality fruits.
All these modifications should be achieved with no loss of yield. These problems are being addressed by Optomize within the following work packages:
Work Package 1: Elimination of side shoots. This is being performed utilising the recently cloned Lateral Suppressor (LS) gene with unique tissue- and stage-specific promoters.
Work Package 2: Optimising leaf inflorescence ratios and leaf shape. Controlled regulation of the Self Pruning (SP) gene will allow the generation of tomato plants with only two leaves between each reproductive meristem, rather than three, which is the current situation. The activity of key molecules such as expansins (which cause loosening and extension of plant cell walls), PINs (which are involved in polarised auxin transport) and Knotted (a homeobox gene) are being modified.
Work Package 3: Synchronisation of flowering. Novel meristem identity genes are being controlled using specific promoters that will both synchronise flowering and produce a fixed number of flowers (and hence fruits) per inflorescence.
Work Package 4: Increasing fruit quality by manipulation of phytochromes. Hypersensitive phytochromes are being expressed in the fruits to potentiate light-dependent processes, such as the biosynthesis of carotenoids and other health- and flavour-promoting substances.
Work Package 5: Increasing fruit quality by manipulation of light signalling. The activity of key regulators of light signal transduction is being modulated in fruits to improve fruit quality as in the previous work package.

Progress to Date
1) Elimination of side shoots: two approaches are being pursued but the one that inhibits LS activity in vegetative meristems is proving to be the most promising.
2) Mobilising architecture genes to optimise leaf-inflorescence ratios: It has been possible to generate plants with sessile leaves but normal flower inflorescences.
3) Modifying the tomato inflorescence: Transgenic plants are being generated and mapping, and subsequent cloning, of the An and S mutations, has begun in earnest.
4) Investigating the role of photoreceptors on the fruit-ripening process: a series of photoreceptor-deficient tomato mutants has been generated and crossed to make a range of different double, triple and quadruple mutants. Many of these have very clear and dramatic effects on truss and fruit development. These have been the focus for assessing the role of individual photoreceptors in the fruit ripening process.
5) focusing on the manipulation of key light signalling molecules: to isolate constitutively photomorphogenic mutants in tomato, several thousand mutagenised seedlings have been screened in darkness. Some interesting mutants were found, one of which is likely to be a null allele in the tomato DET1 gene. The process of performing basic physiological characterisation of these mutants is ongoing, and will be extended to photobiology experiments. These physiological characterisations have revealed that ATV and Af are the most interesting genes that warrant cloning. Mapping populations are currently being studied by CAPS analysis for fine mapping of ATV.

Classified in HORTICULTURE, FRUIT

Scientist responsible for the project

Prof CHRIS BOWLER
VILLA COMUNALE
I-80121 Napoli
Italy - IT

Phone: +39 081 583 3241
Fax: +39 081 764 1355
E-mail: chris@szn.it

References

Project ID QLRT-1999-30357
Organisation Laboratory of Molecular Plant Biology, Stazione Zoologica
Area 5.1.1
Start date 01 December 2000
Duration (months) 48
Total cost 1 601 256 €
Total EC contribution   1 304 330 €
Status Ongoing

The partners

  • Laboratory of Molecular Plant Biology, Stazione Zoologica, Italy - IT
    chris@szn.it
  • Laboratory of Molecular Plant Biology, Stazione Zoologica, Italy - IT
    chris@szn.it
  • Laboratory of Molecular Plant Biology, Stazione Zoologica, Italy - IT
    chris@szn.it
  • Laboratory of Molecular Plant Biology, Stazione Zoologica, Italy - IT
    chris@szn.it
  • Laboratory of Molecular Plant Biology, Stazione Zoologica, Italy - IT
    chris@szn.it
  • Laboratory of Molecular Plant Biology, Stazione Zoologica, Italy - IT
    chris@szn.it
  • Laboratory of Molecular Plant Biology, Stazione Zoologica, Italy - IT
    chris@szn.it
  • Laboratory of Molecular Plant Biology, Stazione Zoologica, Italy - IT
    chris@szn.it
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