Feb 2, 2009

Research Projects

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Genetic research into the heredity of persistence (secondary dormancy)

(2008 – 2011) University of Göttingen, Department of Crop Sciences, Plant-Breeding Unit, Göttingen

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.

The aim of this project is to investigate the heredity of the persistence tendency (secondary dormancy) in winter rape in order to enable varieties with lower secondary dormancy to be bred. The influence of environmental factors and possible connections to valuable seed substances will be quantified. In order to accelerate the breeding process and to select specifically for the secondary dormancy trait, the project will develop molecular markers and provide appropriate genotypes for cultivar breeding.

Experiment description

Genotype variation of the secondary dormancy trait

The genotype variation of the secondary dormancy trait will be investigated in preliminary studies on seeds from three different oilseed rape populations. Since close genetic correlations are known to exist with certain seed substances, wide-ranging studies are being conducted in this area. As well as measuring the levels of certain oils and proteins, specific tests will be used to record the levels of glucosinolate, the plant hormones abscisic acid and gibberellic acid, as well as individual storage proteins like napin and cruciferin.

Molecular marker maps already exist for all three oilseed rape populations. For further experiments, the researchers are looking for the population that displays the closest correlation between the secondary dormancy trait and the relevant genetic markers.

Field trials at several sites

Based on the results from the preliminary studies, field trials will be conducted to examine between 150 and 280 lines of a suitable double haploid population for secondary dormancy and plant substances. The different lines will be grown at two locations for two years each. The project will examine the seeds for the following traits:

• Secondary dormancy: A laboratory test developed at the University of Hohenheim will be used on freshly harvested material to examine the plant’s ability to produce seeds with secondary dormancy.
• Seed weight and seed leaf size: The seed weight is measured using the thousand grain weight. The seed leaf size is assessed visually.
• Seed substances: Storage proteins, plant hormones and other seed substances will be identified using various tests, including ELISA , HPLC (high-performance liquid chromatography) and NIR (near infrared reflection spectroscopy).

QTL (quantitative trait loci) analysis

To enable more precise molecular genetic mapping of the secondary dormancy trait, the information obtained from two locations over two years will be analysed statistically in terms of population development, phenology and seed substances, among other things, and integrated into existing molecular marker maps. This process will take place using QTL mapping, which is used specifically for traits determined by more than one gene (quantitative trait loci (QTL)).

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.

Results

Harvest samples were taken from the double haploid lines as planned in both years of the field trial. An evaluation of all the above-mentioned traits over both years of the trial is not yet complete. The results of the first trial year should be regarded as provisional, since the data from the second year is required to validate them.

A very significant variation was observed for the secondary dormancy trait and for the germination ability. It was found that genotypes with pronounced secondary dormancy have a lower germination ability. In addition, there was a slight negative correlation between the secondary dormancy trait and thousand grain weight.

Within the oilseed rape population there was also a significant variation for all the plant substances measured, although it was not possible to establish any correlation with the dormancy trait.

The QTL analysis based on the secondary dormancy data for one year identified four QTLs on a total of four linkage groups. In total, this accounted for 35 per cent of the phenotypic variation.