Canola and Frost What happens to the seed?

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1 Canola and Frost What happens to the seed? Robert Park Oilseed Specialist MAFRI Growing Degree Days 2004 Examples of low temperature impact on Growing Degree Day accumulation 1 : Location Edmonton Saskatoon Regina Winnipeg 2004 GDD year av. GDD % of 30 year av. 86% 78% 73% 72% Occurrence Lowest since 1977 Lowest on record Lowest on record Lowest on record 1 Growing Degree days (GDD s) are heat units accumulated each day during the growing season. GDD s are determined by adding the high and low temperatures of each day and dividing by two. The base temperature for a specific crop is subtracted from this average. For canola a base of 5 C is used.

2 Minimum Temperatures ( C) June 24, 2004 Minimum Temperatures ( C) August 20, 2004 ( C) Manitoba Canola 2004 Manitoba planted 2.6 million acres in 2004, average yield est. of 30.7 bushels / acres, above average Very cool & wet conditions in all parts of Manitoba. Some more than others 30% early planted, 50% mid to late planting and 20% very late planted. Early frost SW / NW and SE Manitoba Aug 20 Killing frost all of Manitoba Oct 1 The impact of abiotic stress during seed development Depends on 2 major factors level of stress and moisture content in the seed (maturity) - Seed shriveling - Altered protein and / or oil synthesis - Loss of germination - Retention of chlorophyll and other pigments - Precocious germination Green Seed in Canola What are the causes -Frost of immature seeds -Disease - Alternaria Black spot -Hot dry conditions during and after -Variable stands = Variable development -Variety characteristics????? Frost on immature Canola Degrees and duration of the frost and the moisture content of the seed influence the level of damage. - e.g. Frost > -5 at high seed moisture is lethal - Lethal due to the formation of ice crystals that physically disrupt membranes and enzymes.

3 Frost on immature Canola Visual Pod Damage - Heavy damage will result in the pods turning black, total seed collapse, pod drop - Light frost will turn pods white or whitespeckled, some seed collapse???? We generally say that frost causes a disruption in chlorophyll degradation due to enzyme damage. Resulting in high Chlorophyll.. This season we predicted a very high level of green seed following the Aug 20 frost but it didn t happen. Majority of early to mid-late planted canola was all #1 What happened???? Research has shown that chorophyllase activity is activated and synthesized following frost. NEWS TO ME.. Peroxidase activity is inhibited following sub-lethal frost and could be responsible for de-greening failure???? Seed moisture is the over riding factor in chlorophyll breakdown. The wet fall allowed for more breakdown than expected. After a sub-lethal frost there is rapid moisture loss from pod walls, followed by rapid moisture loss from the seed. Min of 20% seed moisture is need for enzyme activity. Frosted canola - go from 50% to 12% in a week. Re-hydration of frostinduced green seeds to 20% moisture for 7 days led to a 25% reduction in total pigment content (Johnson-Flanagan et al, 1994) 40% required for germ. Did this happen in 2004? Maybe???

4 Last time we had green seed Very hot, dry (low humidity) conditions at and after Rapid dry down of the swath - from 40 to 50% moisture to 4 to 7% in a week No time or moisture for chlorophyll breakdown Result - canola in swath for 4 + weeks and limited change in green seed count Common Green Seed Questions Will green seed be reduced in the bin? Will time in the swath simply reduce the green seed count? Will sunlight reduce green seed? Does early contribute to high green seed count? Green seed reduction in the bin???? Time in the swath???? Green seed levels will NOT decrease in bin. 15 to 20% seed moisture is required for enzyme activity Stored canola should be less 10% moisture. Unless the seed moisture is raised back up to 20% moisture it can stay in swath till Christmas. Rain showers, high humidity and morning dues will help. Sprouting????????? Will sunlight reduce green seed? Time of???? Sunlight will bleach the chlorophyll and make it a lighter green. May or may NOT help Very small changes will occur over time. Early will increase your chances of high green seed levels. The environment is the major factor. HOT, DRY, WINDY, LOW HUMIDITY in combination with early is BAD

5 Conclusion Seed moisture seems to be the over riding factor in the breakdown of chlorophyll in the seed. The fall of 2004 was not normal the cool moist fall allowed seed moistures to remain higher than normal. The rate of dry down of the seed the most important factor to consider when assessing green seed issues. Robert Park Oilseed Specialist MAFRI The Manitoba Problem 2004 Table 4. Average Dates of Last Spring and First Fall Frosts and Average Frost-Free Days Average Date of Last Average Date of First Fall Average Frost-Free Days Area Spring Frost Frost Morden, MB May 14 September Winnipeg, MB May 16 September Enzyme activity within the seed breaks down chlorophyll (green) High Chlorophyll levels give the oil a green tinge Consumers like clear golden oil, not green Brandon, MB Portage la Prairie, MB Regina, SK Watrous, SK Saskatoon, SK Indian Head, SK Scott, SK Melfort, SK Lethbridge, AB Lacombe, AB Ellerslie, AB Vermilion, AB May 19 May 11 May 24 May 25 May 21 May 27 June 1 May 28 May 23 May 31 May 24 June 1 September 19 September 29 September 11 September 10 September 16 September 15 September 7 September 7 September 17 September 8 September 11 September Fort Vermilion, AB May 28 August Planting Date & Crop No Frost Damage Top Damage Only Deep Canopy Damage Stage The Manitoba Problem 2004 Seeded Before May 18 5 to 10% Seeded late May & early June off flower but no Seeded in mid to late June just finishing flower Monitor for firmness in seed Wait for Treat as normal Wait for seed firmness and Treat as normal Wait for open fall Wait for seed firmness and Treat as normal and wait for open fall May want to wait for top pods to shatter (frost damaged seed) before May want to wait for top pods to shatter (frost damaged seed) before Be patient as now can not help yield and quality Allow the plant to mature as much as possible No action needed (can be rapid) May want to swath now to avoid shelling losses (can be rapid) Be patient, now can not help yield or quality however be prepared to swath earlier than normal to avoid shelling losses May have lost open flowers and immature pods May continue to flower Wait and see Wait for open fall A minimum of 15% moisture is required for enzyme activity Cool, cloudy & wet weather is the best to reduce Chlorophyll content The opposite for what you need for wheat.