Figure 1. Wheat seed and young seedlings affected by Fusarium graminearum (white arrows). (Photo credit: Brandon Wilt, PSU-PPEM.)
High quality seed is the first input for successful crop production. Using certified seed ensures varietal purity, optimum seed health, uniform and fast germination, reduced number of weed seeds in the seedlot, and a minimal risk for the introduction of noxious weeds in your fields. The high-quality standards of certified seed are obtained during seed production, through phytosanitary inspections and strict disease and weed control.
Commercial wheat (Triticum spp.) and barley (Hordeum vulgare) are self-pollinating plants, with average outcrossing rates of less than 1%. This means that most of the harvested grain will have the same genetic makeup as the crop they were harvested from. Consequently, grain is sometimes used as seed for the next growing season. From a plant health standpoint, using farm-saved seed (grain) is not a recommended practice since seeds are highly effective means for the movement of plant pathogens within a field, and across large areas. The use of farm saved seed can also perpetuate the presence of inocula, the survival structures of plant pathogens that affected the previous crop, as well as soilborne and airborne inocula. In other words, planting saved seed increases your chances of having future disease, weed or stand issues.
Any pathogen accompanying seed either internally or externally is considered seedborne. Seedborne pathogens have the potential to directly affect seed germination and vigor as well as developing plants. Many seedborne pathogens will survive seed processing stages like sorting, cleaning, drying, and storage, and for this reason the use of farm-saved seed is more challenging even if seed conditioning is performed or seed treatments are applied. Therefore, planting certified seed will ensure a clean start for small grain production and the establishment of vigorous and healthy plants.
Here is the list of seedborne diseases of wheat and barley:
|Loose smut (Ustilago nuda)||Barley and wheat|
|Leaf stripe (Pyrenophora graminea)||Barley|
|Net blotch (Pyrenophora teres)||Barley|
|Ergot (Claviceps prupurea)||Barley and wheat|
|Covered smut (Ustilago hordei)||Barley|
|Bacterial blight (Xanthomonas translucens)||Barley and wheat|
|Basal glume rot (Pseudomonas syringae)||Barley|
|Fusarium head blight (Fusarium graminearum)||Barley and wheat|
|Common bunt or stinking smut (Tilletia spp)||Wheat|
|Crown root and root rot (Bipolaris sorokiniana)||Barley and wheat|
An example of a seedborne pathogen that reduces seed germination and causes seedling blight is Fusarium graminearum, the predominant causal agent of Fusarium head blight (Figure 1). Under optimal weather conditions the fungus infects the floret and depending on the time of infection, seeds may not develop, or seeds may be shriveled, chalky white, or pink to purple, and symptomless infection may even occur. While seeds planted from a lot infected with F. graminearum will not grow into plants infected with head scab, emergence may be reduced by 80% and seedlings will be at greater risk of rot.