ECODA project number: B.2.4
Principal investigator: K. Peter Pauls
The presence of green seed in canola at harvest is unwanted, because chlorophyll in the oil is undesirable from a consumer’s perspective and leads to rancidity in the oil. Grade #1 canola contains a maximum of 2.0% green seed. Green seeds occur especially when an early stress event destroys the enzymatic activity that normally breaks down the chlorophyll into colourless compounds.
The current work was based on the hypothesis that genetic variation for the susceptibility of canola lines to stay green exists and sought to find molecular markers related to the trait.
The work on the current project was focused on:
- defining a laboratory treatment of canola that induces the green seed phenomenon
- identifying canola germplasm that differed in the green seed incidence after a cold treatment during the seed maturation period, and
- identifying gene targets that might be involved in the stay-green phenotype in canola.
The work demonstrated that the severity of low temperature damage to canola seed and the resulting occurrence of green seed in the crop depend on the maturity of the seed during the cold period, the severity of the cold treatment and the variety (genotype). It defined a laboratory treatment for inducing the green seed phenomenon (four to 50 fold) in a consistent manner that included: growing plants from various varieties in a growth room (at 22°C light/16°C dark); hand pollination after bolting and prior to flowering; controlled freezing in a programmable freezer twenty days after pollination (DAP) to -4°C; recovery and regrowth of the plants in the growth room until maturity and assessment of the percentage of green seed.
It identified a set of six canola varieties that differ in their susceptibility to form green seed during a cold stress and showed that the differences observed among the varieties in the laboratory screen were correlated with the frequencies of green seed observed in the OOPSC Spring Canola Co-op Trials (2009).
The work also examined global gene expression patterns in control and treated seed by RNA-Seq to examine the expression patterns of genes coding for enzymes in the degreening process in normal and freeze-treated tissues. The differences between treated and control and sensitive and tolerant genotypes are being used to identify correlations between gene expression and the stay green trait. In the future, polymorphisms in the genes associated with the stay green trait can be used for selecting for lines that have a low incidence of staying green.