Potato Grower

46 POTATO GROWER | SEPTEMBER 2017 Diggin' In Diggin' In Diggin' In Diggin' In Diggin' In STORAGE| By Nora Olsen, University of Idaho Understanding potato dormancy Down for a Nap When describing storability of a potato we often use the term "dormancy." A dormancy value or duration gives insight into how long the potato will store before it initiates sprout development. Knowledge on dormancy length provides information on selecting varieties for short- to long-term storage, planning for proper timing of sprout inhibition products, and marketing of the potatoes. For process and fresh market potatoes, detrimental quality concerns develop once sprouting begins. These concerns include changes in carbohydrate status, increase in respiration rate, additional weight loss, and storage management issues such as impeded airflow. Seed growers may need to accelerate or retard sprout development depending on the time of year and intended seed market. The biological advantage for a dormancy period in a plant is survival of the species. The inherent dormancy of potatoes allows for most varieties to overwinter, barring any freezing conditions, and re-sprout in the spring, thereby reproducing and perpetuating the species. Tuber dormancy keeps the potatoes from sprouting in the fall and therefore reducing chances of the species being killed by unfavorable winter conditions. We have come to know this effective survival mechanism all too well when trying to control volunteer potatoes. Conversely, the tuber dormancy period provides great advantage in storage to allow for many months of storage with or without sprout control product application. Quality can be maintained when using a tuber's inherent dormancy traits to our advantage. There are three classes or types of dormancy that can be described in potatoes: 1. Endodormancy occurs after harvest and is due to the internal or physiological status of the tuber. In this situation, even if tubers are placed in conditions favorable for sprout development, sprouting will not occur. 46 POTATO GROWER | SEPTEMBER 2017 VARIETY Russet Burbank Alpine Russet Classic Russet Umatilla Russet Owyhee Russet Premier Russet Clearwater Russet Highland Russet Ranger Russet DAYS OF DORMANCY WHEN STORED AT: 42 degrees 175 185 155 145 140 120 110 110 100 45 degrees 155 165 130 130 120 100 90 85 85 48 degrees 130 140 100 100 100 85 85 80 80 Understanding the dormancy of different varieties will help growers determine the best environment to create in their storages. Approximate dormancy length (days after harvest) of several russet varieties at three storage temperatures. Dormancy length is defined as 80 percent of potatoes having at least one sprout greater than 5 millimeters in length.

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