Seed diagnostics offer insight into crop performance

Today’s farmers pride themselves on using technology and science in their operations. They soil test to formulate the right nutrient package needed to maximize yield, use specialized seeding equipment, GPS and variable rate technology to ensure nutrients are accurately placed, and so on.

Yet many farmers tend to forgo hightech diagnostic tools when it comes to seed selection. Seed is most often chosen on the basis of variety and germination, with the idea that as long as the variety has good germination it will grow well. But seed diagnostics can offer growers so much more.

Which is why, besides germination, farmers might want to think about testing their 2017 seed for vigour and the presence of disease. In a presentation at the SeedGrowth Solutions Expo held in Saskatoon in March, Holly Gelech, from BioVision Seed Labs, said there was heavy disease pressure in 2016 therefore seed quality could be compromised.

To illustrate her point, Gelech talked about fusarium graminearum, which may pose a serious problem for farmers this growing season. Last winter, fusarium graminearum was detected in 35 per cent of Alberta wheat samples submitted to BioVision. The average detection level for the previous four years was just 20 per cent.

This is a huge increase in a province where fusarium is not yet considered a major problem in cereals. Thankfully, the severity level in the samples was relatively low, with an average infection rate of two per cent this year. Still, this means two out of every 100 seeds in over a third of the wheat samples tested was infected with fusarium graminearum.

In Saskatchewan and Manitoba, where this disease is solidly established, the news is even worse. Fusarium graminearum was detected in 87 per cent of Saskatchewan wheat samples this year and in 92 per cent of Manitoba wheat samples. The average fusarium graminearum severity level for Saskatchewan wheat samples was 10.8 per cent while in Manitoba it was 12 per cent. Winter wheat, which is highly susceptible to fusarium, saw detection rates of 16 per cent in Alberta samples and 100 per cent in samples from Saskatchewan and Manitoba!

BioVision uses 100X magnification when examining seed for signs of disease as fusarium-diseased seed can look normal to the naked eye. The lab uses DNA testing and/or a plated test when looking for fusarium.

The DNA test is specific to the fusarium graminearum species — and it’s quick. In just two days, DNA from 400 to 600 seeds is extracted and analyzed to see if the seed has been exposed to fusarium graminearum. It’s also a highly sensitive test, able to detect disease levels at 0.125 per cent infection rates. However, the DNA test cannot tell you disease severity or if other fusarium species are present within a sample. For that there’s the plated test.

This consists of first washing 200 seeds in a bleach solution to destroy any surface bacteria that can impact fusarium growth. The seeds are then placed in a fungal growing medium and incubated for five days at 30 C. This initiates seed-borne fungal growth.

Gelech warns there could be multiple fungal pathogens on the seed so it takes visual examination to determine if the fungal growth is a critical disease such as fusarium, root rot, mildew or blackpoint, or if it’s a less critical storage fungus.

Not just for cereals

Cereals are not the only crops threatened by seed-borne diseases. At the Expo, Trevor Blois with 20/20 Seed Labs spoke about seed-borne pulse diseases. Indeed, pulse and canola diseases were both higher in 2016, with ascochyta being the prime concern for pulse growers.

Blois said this disease can cause 30 to 50 per cent yield loss in peas, up to 70 per cent yield loss in lentils, and total yield loss in chickpeas. Chickpeas have very high levels of seed-to-seedling disease transmission, so growers must use seed with very low disease levels — less than 0.25 per cent.

And yet, this past year, 60 per cent of chickpeas tested positive for ascochyta, with an average infection rate of 1.5 per cent — well above recommended levels. Ninety per cent of peas tested were positive for ascochyta, with five per cent infection rates. With numbers like that, can you really afford not to test pulse seed for disease?

Besides ascochyta, seed labs regularly test for botrytis, anthracnose, sclerotinia and aphanomyces in pulses and blackleg, alternaria, and clubroot in canola seed.

As well as testing for seed-borne disease, consider asking for a vigour test, also known as a cool stress test. A germination test typically involves placing 200 seeds in a blotter soaked with water and potassium nitrate (used to break dormancy), then incubating them in a growth chamber at 20 C to see how many germinate under ideal conditions. For the vigour test, the growth chamber temperature is only 7 C, to mimic the less than ideal cool soils that farmers typically seed.

This year Gelech compared the germination and vigour test results of 100 random samples received in the lab. She treated a subset of these samples with recommended rates of various seed treatments so she could compare the germination and vigour of untreated versus treated seed. Untreated seed germination was 89 per cent, and vigour was 86.7 per cent. Treated seed germination was 94.5 per cent, and vigour 91.2 per cent. These results show that seed treatments improved germination.

Farmers should also consider getting a 1,000 kernel weight (TKW) test on their seed so they can set seeding rates more accurately to achieve target yields. There can be a big difference in TKW from seed lot to seed lot, even of the same crop, so one size does not describe all seed. Unless you know the TKW there is no way you can accurately set a seed drill for the desired plant stand.

While no seed test or diagnostic can guarantee a bumper crop, it can tell you that seed quality is not the issue should you have a disappointing harvest.

On a personal note …

After writing this story, I wasn’t surprised to find out after talking with six prairie seed cleaning plants, that very few farmers test their seed for anything other than germination.

Five out of the six managers said that either seed diagnostic testing is not normally done or very few farmers do any seed testing other than germination. One manager said that most of his customers do not test for seed diseases and some not even for germination.

Often when I research an article, I have an “aha” moment. I learn something new. I discover a practice or product that I want to try on my own farm. I find a new way of tackling a problem — sometimes even before I realize I have that problem.

Murray Van Petten, manager of the Camrose County Seed Plant, triggered such a moment for me when I interviewed for this article. He estimates only about one per cent of the commercial farmers he cleans seed for regularly test for diseases other than fusarium graminearum. (In Alberta, by law, all seed must be tested for fusarium graminearum before it can be cleaned.)

Van Petten says many farmers balk at the cost of diagnostic testing. However, he points out that the $150 to $200 cost for a full fungal scan is a fraction of the cost that a farmer spends on seed treatment before even knowing if and what seed-borne diseases he’s treating for.

Over the past winter, Van Petten encouraged farmers to try additional seed testing to find out what diseases might be present and to make a more informed choice about which seed treatment would be best. He also hopes some of those who did test will also test the harvested seed this fall to see the effects of their treatment decision. If the harvested crop shows a decrease in seed-borne disease, it will validate their decision to treat.

By showing farmers the comparatively low cost of seed diagnostic testing and assisting farmers to select seed treatment products based on actual disease presence, about five per cent of Van Petten’s customers opted for additional diagnostic testing this winter.

While Van Petten opened my eyes to the potential value of diagnostic testing, I have to admit I only test for fusarium graminearum, germination and vigour. I zero-till and often seed into cool damp soils, which are conducive to disease and slow germination.

I also want to protect against both seed-borne and soilborne diseases, so I treat all seed every year. I rotate between seed treatment chemistry annually. Through field trials I have found seed treatment consistently increases yield on my farm through disease suppression, improved germination and plant health.

Is it possible that I am spending more than I need by treating seed for diseases that I may not have? Yes. However, I consider seed treating not only to be effective, but also as insurance.

Simply knowing what seed-borne diseases may be present likely wouldn’t change my practices. However, other seed diagnostic tests like TKW are worth considering. After all, yield hinges on plant stand and plant health.