How To Protect Cut Potato Seed From Infection
July 19, 2024 Most potato growers cut seed tubers into pieces for planting, mainly because they are more cost effective than using whole seed, but cutting the seed creates a wound that allows moisture loss and is an entry point for bacteria and fungi. This problem can be circumvented if the cut surface undergoes a natural wound-healing process.
Wound Healing
Wound healing is a two-step process. First, a layer of suberin (a waxy, fatty compound) is deposited below the cut surface to seal the wound. This process can start immediately and is usually complete in two to four days. Next, a wound periderm is formed. This is a protective layer of corky cells that serves as a skin replacement. The entire process can take a week or two under ideal conditions.
The healing process is helped by plenty of oxygen, temperatures around 55°F, and a humid environment.
If the seed pieces are planted immediately after cutting, then the wound healing process will take place in the soil, provided the conditions are favorable.
Precutting Seed
Precutting is the practice of storing cut potato seed pieces for a period before planting. The precut seed is usually stored in an environment that encourages rapid wound healing, which can be useful when soil conditions are not favorable.
Precutting can also be used to overcome dormancy and promote more uniform sprouting, especially for cultivars that tend to emerge slowly (e.g., ‘Shepody’ and ‘Yukon Gold’) or for seed that is physiologically young. Another advantage of precutting is that growers get more time to focus on the cutting process without also having to worry about planting.
Some growers precut seed and store it in bulk trucks for a few days before planting, but this may not be the best environment to encourage wound healing. It is better to store precut seed in bins or piles (no more than 6-feet deep) where temperature, humidity, and airflow can be adjusted.
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The temperature should be maintained at 50 to 55°F, unless the seed is physiologically aged and is likely to sprout within a few days, in which case it should be kept cooler. Precutting is not recommended if the seed is old and has already sprouted.
Relative humidity should be about 90% to 95%. The humidity prevents desiccation of new periderm cells. It is important, however, to avoid condensation on the seed pieces, because a water film can restrict oxygen and promote the establishment of soft rot bacteria. Warming the seed tubers to the same temperature as the storage environment before cutting can discourage condensation in the pile, and it cuts better with less tissue tearing and bruising.
Airflow is needed to provide oxygen and remove carbon dioxide, and to help regulate temperature. It may also help to remove any condensation that forms on the seed pieces. Ventilation can be provided through storage system air ducts, but excessive air flow can dehydrate freshly cut seed, so it may be necessary to reduce the fan speed or block some of the vents.
The precut seed should suberize in three to four days. Apply gentle pressure across the seed piece to test suberization. If a layer of dead cells pushes off the surface, then it is not ready. Once suberized, the seed pieces can be planted. Or you can wait another week or two for the wound healing process to be complete.
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