This is, perhaps, one of the most valuable diagnostic tools available to growers. It was developed by and is exclusive to 20/20 Seed Labs Inc.
Why do a Fungal Screen™?
Seed-borne pathogens can cause a host of problems with germination, vigour and seedling health, which can, in turn, impact stand establishment and, ultimately, yield potential.
If these pathogens are identified prior to seeding, growers can take action to minimize the risks, either by selecting a seed treatment that controls the identified pathogens, or deciding to not use the seed lot altogether.
It is always beneficial to learn why crops may have performed poorly in the field. If a pathogen was a contributing factor, a professional diagnosis is helpful, since many diseases show very similar field symptoms.
Disease pathogens can be categorized into four groups, as follows:
- Seed rots and seedling blights. Fungi such as Fusarium spp. and Cochliobolus sativus (Bipolaris sorokiniana) may cause the death of seeds or of seedlings before or shortly after emergence.
- Foot and root rots. Seedlings affected with Fusarium spp. and Cochliobolus sativus (Bipolaris sorokiniana) and that survive the seedling stage might die later, or ripen prematurely, producing fewer heads, resulting in reduced seed set and/or shriveled seed.
- Leaf blights. Septoria spp. can cause severe spotting on leaves and glumes, resulting in reduced seed set and shriveled seeds.
- Head blights. Three species of fusarium (F. avenaceum, F. culmorum and especially F. graminearum) cause floret sterility and poor seed fill, causing significant yield loss. These species also produce mycotoxins that can be harmful to certain livestock and humans. Other species of fusarium are associated with head blight, as well as foot and root rots.
How is a Fungal Screen™ Done?
200 seeds are surface sterilized, placed on a growth medium and allowed to germinate.
A qualified analyst examines the colonies produced and identifies the pathogens as follows:
Pathogenic Fungi – Common Name/Symptoms
Cochliobolus sativus – Seedling blight, foot and root rot or spot blotch (leaf blight)
Fusarium graminearum – Head blight
Fusarium spp. – Seedling blight, root and crown rot, and head blight
Pyrenophora spp. – Leaf blight (leaf stripe, net blotch and tan spot), and seedling blight (oats)
Septoria spp. – Leaf blotch
Saprophytes or Weak Pathogens such as: Alternaria spp., Cladosporium spp., and Epicoccum spp. –
Commonly found pathogens that can become more aggressive during delayed harvest and through mechanical damage. These fungi can cause seed discoloration resulting in lower seed grades.
Storage molds such as Aspergillus spp. and Penicillium spp. – These are found on the seed surface and can damage improperly stored seeds.
- This test gives the percentage of infected seeds to 0.5%.
- This test takes 7 days to complete.
How do I Use Fungal Screen™ Results?
Seed that tests positive for the presence pathogens is not necessarily unusable.
Cochliobolus sativus, for example, causes common root rot and can significantly reduce germination. However, when a seed lot that tests positive for Cochliobolus sativus is treated with a seed treatment registered for common root rot, it can be perfectly viable, germinate well and produce healthy plants.
Although there are no industry standards for the above mentioned pathogens other than True Loose Smut of barley (Please refer to Grade Tables II and III of the Seeds Act for the allowable limits), it is important to remember to correlate the germination results with the results of the Fungal Screen. For example, if a germination result is low due to a seed-borne infection it is possible to re-test that same seed lot in the laboratory with a seed treatment. We can hand-treat your seed sample to ensure that the pathogen is controlled and determine if there is an improvement in the germination result.
Most seed treatments will control common seed- and soil-borne diseases and smuts by protecting seed and emerging seedlings, and provide an economical advantage when compared to untreated seed.
Growers should always be aware of overall quality of their seed and use high germinating, vigorous, disease free seed whenever possible. The Fungal Screen™ is another tool that allows them to make a more informed decision about seed use.
More Information: The Fungal Screen™ is a snapshot of one aspect of seed quality and is most useful when used in conjunction with other seed quality tests. 20/20 Seed Labs Inc. offers a number of testing packages to help you find out exactly what you need to know about your seed. For more information, see our Agronomic Test Packages.
The responsibility for seed utilization under this report with respect to any result or specification rests entirely with the client.