Jan 30, 2009

Research Projects

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How reliable is the cultivation of male-sterile maize as a means of restricting dispersal?

(2008 – 2011) Julius-Kühn-Institut, Federal Research Centre for Cultivated Plants (JKI), Institute for Biosafety of Genetically Modified Plants

Topic

When it comes to assessing the safety of transgenic plants, the possibility of the new genes being dispersed by pollen or seeds plays an important role. Therefore, strategies are being developed around the world that aim to prevent pollen- and seed-mediated gene transfer (biological confinement strategies).

Cytoplasmatic Male Sterility (CMS) is a naturally occurring characteristic that has been described in various plant species, including maize. Plants with this characteristic do not produce fertile pollen. This makes CMS a suitable tool for biological confinement, since unlike other sterility concepts, it is not necessary to carry out sterilisation of the male flowers using painstaking mechanical or genetic methods.

Cytoplasmatic sterility can however be reversed through the activation of specific genes or by extreme environmental conditions, such as heat, drought or torrential rain. However, if a method is to be used for biological confinement, it needs to display a high level of trait stability and reliability.

The aim of the project is to record quantitative data about the dispersal of CMS maize plants to neighbouring maize plots in three different environments. The data should enable conclusions to be drawn about the reliability of CMS as a biological confinement method.

Experiment description

Maize cobs from a white-grain variety. The plants were fertilized with pollen from a yellow-grained CMS maize variety. The proportion of yellow grains shows how much pollen from the yellow-grained variety was able to fertilize the white variety.

Previous projects managed to identify ten CMS maize varieties, six of which display stable sterility traits and four of which display fluctuating sterility traits. The latter produce both sterile and fertile pollen. The yellow-grain CMS maize varieties are grown next to a maize field with a white-grain variety. If white-grain maize is fertilized with pollen from yellow-grain varieties, a yellow grain develops. The cobs are harvested when they are ripe. The proportion of yellow grains indicates how much pollen from the neighbouring CMS plots was able to fertilize the plants in the harvest plots.

The trials are being conducted at three sites, with three repetitions at each (at the Julius Kühn-Institut in Braunschweig, at BioOK GmbH and at the Bayerische Landesanstalt für Landwirtschaft). During the growing seasons, various characteristics of the maize plants, e.g. plant height, start and end of flowering and ripeness of the panicles, are recorded.

In this project phase the following questions are of interest:

  • Do the plants produce anthers and pollen in field conditions?
  • If pollen is produced, is it fertile?

The variety with the lowest dispersal potential and the variety with the highest dispersal potential (best- and worst-case varieties) will then be planted at varying distances from the recipient plot in realistic conditions. The following questions will be investigated:

  • How are the two CMS maize varieties distributed in the pollen recipient crop (white maize)?
  • What distance needs to be left between the recipient crop and the CMS variety in question to avoid exceeding the threshold for outcrossing when genetically modified maize is planted?

Once the field trial is completed, a statistical analysis of the collected data will be carried out.