Nov 10, 2010

Research Projects

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Forecast model for volunteer rape

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

Topic

Rape seeds can survive for a long time in the soil, and often do not germinate until years later, appearing as volunteer plants in the following crops. If genetically modified oilseed rape is grown, it can lead to the undesirable mixing of GM rape in subsequent conventional rape crops. Under controlled conditions in laboratory and field trials, the key factors influencing seed survival were found to be the frequency with which oilseed rape was grown on a field, the post-harvest tillage of oilseed rape stubble and the variety chosen.

The aim of the project is to develop a forecast model for the emergence of volunteer rape plants and to expand on existing knowledge. To this end, phenotypic scoring of volunteer plants will be conducted on plots on working farms and the key factors influencing the survival of rape seeds will be identified with the help of field records.

The project is part of the joint project on “Developing and testing confinement strategies for oilseed rape”. The network partners – the University of Hohenheim, the University of Göttingen and the Julius Kühn-Institut (JKI) – are collaborating on laboratory analyses, the use of trial fields and data exchange for modelling.

Experiment description

Volunteer rape in farming practice

A nationwide survey will be conducted to find a representative number of fields on which oilseed rape has been grown over the past ten years and on which there are plans to grow oilseed rape in the 2009/2010 season.

The field files for these plots will be evaluated to determine what the farming practice has been over the past ten years. All relevant cultivation data will be statistically evaluated and used in the volunteer rape forecast model.

Field trials to identify the volunteer rape

In the 2009/10 and 2010/11 growing years, phenotypic scoring (assessments) of volunteer rape plants will be carried out on selected oilseed rape plots. Since it is difficult to differentiate between volunteer rape plants and cultivated rape plants, two complementary methods are used to identify the volunteer plants:

• Assessments on unsown areas During sowing, gaps (unsown areas) are intentionally left in the oilseed rape crops.
• Assessments in semidwarf oilseed rape crops Semidwarf rape hybrids are much shorter than normal varieties, so the volunteer plants stick out.

The assessments on unsown areas took place in autumn 2009 and 2010. The assessments in the semidwarf rape crops took place in spring 2010.

Identifying the genotype of volunteer rape plants

Oilseed rape had been grown several times on almost all the farm plots in previous years. Different varieties had been grown. In order to obtain information about the influence of the oilseed rape genotype on the number of volunteer plants, leaf samples are taken from volunteer rape plants and examined to determine their variety of origin using PCR methods.

Volunteer rape forecast model

The aim is to develop a forecast model that will assist farmers with their rape cultivation plans by predicting the expected number of volunteer rape plants as a function of variety, site and cultivation measures. The tool can be particularly useful when switching from a transgenic to a conventional oilseed rape variety, where farmers are trying to avoid cross-contamination. The data used in the model will include farming-related information from field files and the results of the assessments of volunteer plants.

Results

Assessing volunteer rape plants

By spring 2010, volunteer rape plants had been assessed on a total of 78 plots. Of these, 31 involved assessments on unsown areas, while assessments in semidwarf rape hybrids were conducted on 47 plots. Further surveys using assessments on unsown areas are planned for autumn 2010. Preliminary evaluations reveal that the site has an influence on the number of volunteer plants. This is presumably due in part to the cultivation history of the field. For instance, the greater the role of oilseed rape in the crop rotation, the greater the number of volunteer rape plants. By contrast, numbers of volunteer plants fall when the time between the rape harvest and the first stubble tillage is increased.

Volunteer rape forecast model

In order to be able to improve forecasts of volunteer rape numbers in future, a forecast model is being developed. At the moment, important information is still being obtained that will be incorporated in the model later on. This includes information on the site (soil and climate data), on the crop rotation, tillage, the genotype of the emerging volunteer rape plants and information on the use of herbicides in the crop following the oilseed rape crop.