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Development of an environment-friendly F1 hybrid breeding technology

The F1 hybrid is a proven breeding tool since it results in better crop yields and the natural protection of breeders' rights. It relies on parental homozygosity and, in most crops, reversible male sterility. The former ensures the uniformity of the hybrid crops, the latter allows large-scale hybrid seed production without emasculation. Instead of repeated self-pollination, a rapid way to reach 100% homozygosity is through microspore embryogenesis followed by chromosome doubling to produce doubled haploid (DH) plants. Unfortunately, this is only feasible in a few crops and cannot combine with male sterile systems. As a multidisciplinary consortium, HybTech will use in vivo metabolic starvation to establish a widely applicable breeding technology that can combine reversible male sterility and production of DH plants. It will provide a rapid way to generate new F1 varieties without releasing transgenic pollen into the environment.

The objectives of this project are:
1) to develop a male sterility system in tobacco, tomato, chicory and rice, where the sterility is caused by depleting one of the four enzymes from developing microspores
2) to develop a system to produce doubled haploid (DH) plants from recalcitrant crops by using in vivo starvation to trigger the switch from pollen maturation to embryo development, followed by microspore culture
3) to combine 1) and 2) into a rapid breeding procedure for F1 hybrid seed production
4) to develop strategies for restoring male fertility by spraying plants with the missing metabolites or by in vitro microspore maturation.

Progress to Date
1) All cloning work has been finished and 20 constructs have been made for the dominant negative mutation, anti-sense suppression and RNA interference (RNAi).
2) One monocot tapetum-specific promoter, CA55, has been introduced for rice transformation.
3) Transgenic plants have been obtained in Arabidopsis, tomato, chicory, tobacco and rice.
4) Partial and total male sterility has been observed in the transgenic Arabidopsis, chicory, tobacco and tomato carrying some of these constructs, suggesting that the working concept could be valid.
5) Petunia transposon population has been screened for the insertion in two key metabolic genes and candidate insertions have been identified.
6) A GC-MS method has been developed which can be routinely applied for microspores, embryos, pollen and anthers.
7) The HybTech website ( is running both a public and a partner-only domain for the exploitation of findings and communication.


Scientist responsible for the project

Droevendaalsesteeg 1 Box 16
6700AA Wageningen
Netherlands (The) - NL

Phone: +31 317 477330
Fax: +31 317 418094


Project ID QLRT-1999-30902
Organisation Plant Research International B.V.
Area 5.1.1
Start date 01 March 2000
Duration (months) 42
Total cost 2 011 986 €
Total EC contribution   945 322 €
Status Ongoing

The partners


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