Growers need to know their seed quality for 2011
By Bruce Barker
With delayed seeding, monsoon rains and killer frosts, the growing season of 2010 left a mixed bag of seed quality for 2011. At 20/20 Seed Labs Inc., president Sarah Foster says seed dormancy, frost damage and disease have been issues seen with samples sent to the lab during the winter. “Dormancy is our biggest challenge this season. It has taken us several attempts to break dormancy on several seed lots arriving from areas that had seed harvested early. Wheat is the most affected, barley next, then oats,” she says.
Foster explains that dormancy is a state in which the seed is viable, but for various reasons cannot germinate. She says the key to breaking dormancy is to determine which type of dormancy is present. From the harvest of 2010, exogenous dormancy is predominant. Exogenous dormancy is broken into three sub types, one of which is physiological dormancy. Physiological dormancy is caused by chemical inhibitors that prevent the embryo from developing, and is usually associated with high moisture, a short drying down period and poor harvest conditions.
20/20 Seed Labs typically breaks dormancy in the laboratory with a three-day pre-chill stratification period, and the use of a growth promoter such as potassium nitrate (KNO3). However, in many cases this regime was not enough to completely break the dormancy and 20/20 Seed Labs was retesting with a seven-day pre-chill period and potassium nitrate over the fall and winter. “This naturally caused delays with germination, as we are often retesting as many as three times to obtain the best possible result,” says Foster. “This regime gives us results on the potential germination that will be accomplished next spring.”
Foster says seedling vigour is affected too, because often seed will not respond to low temperature stress and that causes the seed to stay in its dormant state. As a result, the tests may not truly reflect the quality of seed. “We end up with high germination and low vigour, which may not be the true quality. We sent our clients a note with their samples last fall that to be certain of seed quality this spring all seed should be retested for both germination and vigour.”
Frost damage also causes concern
With frost in areas across the Prairies, frost damage is showing up in tested samples. Frost-damaged grain is white or grey in colour, smaller, often shrivelled with a wrinkled texture. Oats may be black and lack the usual glossy coating. Often symptoms are not apparent and the damage is only identified through a germination or vigour test. “I particularly found it interesting to monitor germination samples this year, because producers were sending in several samples at a time; some seed would be dormant, some frost damaged and some completely fine. It really did depend on time of harvest, and the lay of the land,” says Foster.
Frost damage is identified by seedling abnormalities displayed during a germination test, explains Foster. The small plants will appear to be grainy, with little or no leaf development. Often the coleoptiles will be empty; they may also appear shrivelled, or twisted, unlike a normal seedling, which is strong and straight. Severe damage will completely kill the seed; the dead seed in a germination test is black and very soft.
Foster says frost is an issue because it continues to deteriorate the embryo during the winter, while in storage. The germination and vigour test results produced in the fall are not always the same in the spring. She recommends retesting in the spring, as well. “I think it is safe to say that a seed with frost damage that is making grade in the fall of the year should, with good storage, maintain a reasonable germination,” says Foster. “However, if the test results are lower than 85 percent germination, with all of the remaining seed being dead or abnormal due to frost, then one should consider finding new seed.”
Foster says severe frost was seen on oat samples sent in during the fall of 2010, with some samples showing zero percent viability. Wheat was a close second, and barley was third. However, she says not all cereal samples were showing frost damage, and many samples were “stellar.”
Seedling abnormalities categorized
In addition to abnormalities caused by frost, mechanical damage on peas, beans and canola was prevalent in samples submitted in late 2010. Foster says mechanically damaged seed will result in seedlings that have no roots or shoots. Often both structures are missing, but in most cases only one or the other is absent. This is caused by threshing the seed when it is too dry, or processing the seed when it is too dry without taking the necessary precautions to prevent splitting. Peas and beans are particularly susceptible, and these seedlings will not develop normally.
Preharvest desiccation on any crop that was not evenly mature also has caused abnormal seedlings. The seedlings will have all the essential structures, but will be deformed with short, wiry roots that want to grow in opposite directions. “Unfortunately, abnormal seedlings are incapable of normal growth and are therefore incapable of developing into healthy seedlings in the field,” says Foster.
Foster says the presence of disease has been very high. Cereals are affected by Septoria, Eppicocum, Fusarium and Cochliobolus. Peas can be affected by Ascochyta and Sclerotinia.
Ultimately, Foster says growers should ensure the seed they are planting had three critical seed tests conducted in conjunction with a germination test: a vigour test, a thousand kernel weight test and a disease diagnostic profile. “The three critical tests can assist in determining the correct amount of seed to purchase (or clean) and then plant at an appropriate seeding rate. These tests form the basis for a uniform seedling establishment, which should be used to achieve an optimal plant stand. These factors can have a large influence on nutrient utilization, herbicide utilization and crop maturity,” says Foster.