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Keeping the green in lentil

The equation is easy enough; the greener the lentil sample, the higher the value of the crop. But keeping that green is not quite as easy. The loss of green lentil seed coat colour desirability has been estimated to cost producers millions of dollars annually, says Blaine Davey, a producer at Wilkie, Saskatchewan, who conducted research into green colour retention while at the University of Saskatchewan.


April 30, 2010
By Bruce Barker

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The equation is easy enough; the greener the lentil sample, the higher the value of the crop. But keeping that green is not quite as easy. The loss of green lentil seed coat colour desirability has been estimated to cost producers millions of dollars annually, says Blaine Davey, a producer at Wilkie, Saskatchewan, who conducted research into green colour retention while at the University of Saskatchewan.

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DuPont’s Acurum instrument.(Photos courtesy of Blaine Davey)
 
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Top: Lentil sample with index score of 2.6 (more desirable).
Bottom: Lentil sample with index score of 8.2 (less desirable).


 

Lentil producers and processors report that the level of quality loss differs from year to year and may be dependent on variety. Davey, along with Dr. Bert Vandenberg at the university’s Crop Development Centre, looked at genetic factors and how swathing or desiccation can impact green seed colour.

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The researchers grew 15 green lentil varieties at two locations over two years. The lentils were either swathed or desiccated with Reglone at the recommended timing, when the seeds rattled inside the pods on the lower third of the canopy. Typically, the recommended stage is reached in late July for early varieties in the drier southwest through to the first two weeks of August further north and east. The green lentil varieties were CDC Greenland, CDC Glamis, CDC Grandora, CDC Plato, CDC Sedley, CDC Sovereign, CDC Vantage, CDC Viceroy, CDC Meteor, CDC Richlea, CDC Milestone, Laird, Eston, 1048-8R, and 1294M-23.

An Acurum instrument supplied by DuPont Canada was used to objectively measure seed coat colour. The Acurum machine was developed as a grading tool to reduce grade variation among individual graders. It assigns each lentil seed an arbitrary number describing its colour. “Swathing a green lentil crop almost always produced a better quality green lentil sample with greener seed,” says Davey. 

However, swathing did not always produce a better sample. Davey says that one issue that arose with swathing during an abnormally wet harvest was an increase in disease incidence on the seed coat. Some level of seed cleaning would have been required to maintain a grade of Canada No. 2 or better. Swathing also brings the added risks of windblown swath losses, slower dry-down and sprouting with cool, damp weather. 

On the other hand, desiccation did not produce a more desirable green seed coat when compared to swathing at either of the two test locations. With desiccation, the risk of grade loss increases because samples are more likely to bleach or darken as a result of exposure to sun and rain, which occurs when they are left standing. 

Since weather is uncontrollable, though, the researchers say that swathing is an individual decision based on equipment, time and target market. In general, they say that the growers who swath have the fewest acres and are aiming for the highest possible quality. Desiccation is favoured by large acreage growers who want to get the most in the bin in the shortest period of time. 

Varietal differences as well

Large differences for green seed coat desirability in lentil were found between the varieties. The most desirable variety was 1294M-23. It has recently been a parent in many crosses developed by Vandenberg’s lentil breeding program. CDC Greenland and CDC Grandora produced the most desirable green seed coats of the registered varieties available to lentil producers. The breeding line 1048-8R, produced the least desirable green seed coat colour. CDC Milestone and CDC Vantage were the two registered varieties that produced the least desirable green seed coats.

Vandenberg explains that breeders have tried to move away from varieties with sharp seed edges like Laird, because they tend to chip, especially when the seed is dry and the seed coat is more brittle. “In the breeding program, we now have a strong focus on improving the ability to retain green colour in the seed coat,” explains Vandenberg. “For example, when Eston was replaced with Milestone a few years ago, we gave up some colour retention for ascochyta blight resistance, but the release of Viceroy combined everything in one package.”

Vandenberg and Davey say that the best strategy for harvesting a good quality green lentil starts with seeding early and using varieties that tend to retain green colour. They say that good weed control and attention to potential disease development is also part of the package. Timing of preharvest desiccation or swathing is critical. 

While the best laid plans can go astray because of the weather, good timing and a little good luck will go a long way to producing a high quality green lentil crop.