Sprouting disorders due to physiological age

Kind of organism : Disorders and damages

Detection method : Visual

All diseases & pests

The physiological changes of the tuber (incubation or physiological ageing) is an irreversible phenomenon which takes place in two stages.


The first stage, which begins immediately after the harvest, is a rest period during which the tuber is unable to sprout, even under ideal conditions. It is in a state of vegetative rest or deep (innate) dormancy.

The length of dormancy can vary according to the cultivar and conditions in the year of production. It may range from 17 to 40 weeks starting from tuber formation until the appearance of the first visible sprout (around 1 mm in length) on tubers stored in darkness immediately after the harvest, at 15°C with a relative humidity above 85%.


The second stage, sprouting, consists of three successive phases reflecting the degree of incubation of the seed tuber:

The growth vigour of the plant (photo 13) is closely related to the physiological state of the mother tuber at the time of planting.

Symptoms on foliage

Despite all the care given to the crop, over-incubated seed potatoes (phase III) have a slow, staggered, heterogeneous emergence. The developing aerial parts remain stunted and the root system undeveloped, rendering the plants vulnerable to drought. The slow growth of the shoots makes them extremely susceptible to attacks by soil pathogens (especially black scurf). As the tubers are formed early, the period of vegetation is shortened (which can be beneficial in the case of early potatoes). In extreme cases, notably when the temperatures immediately following planting are low, or when the tubers are desprouted, the plant tuberises in the soil with no preliminary formation of aerial stems.


Conversely, under-incubated seed potatoes (in phase I) result in late emergence and a limited number of stems (numerous single-stem plants) but subsequently have normal vigour. This phenomenon is observed mainly with early export and prompt planting in autumn.


Facteurs de risque

The tuber’s physiological ageing speed, or incubation speed, differs with each cultivar. It is rated in the French catalogue of potato cultivars from 1: very rapid (highly susceptible to incubation) to 9: very slow.

The age of a tuber of a given cultivar at a given time increases in proportion to the length of time since its initiation (chronological age), and to the temperature at which it was stored after being harvested. Cultivars characterised by slow physiological development tolerate basic storage conditions.

The knowledge acquired concerning the physiological age of seed potatoes has found a practical application in low-temperature storage and the use of cold rooms (2 to 4°C). This provides high-quality seed potato tubers that are physiologically suitable for conventional planting.

Apart from physiological ageing, seed potatoes of some cultivars, stored at too low a temperature or air moisture, may suffer dehydration of the eyes which may totally or partially inhibit sprouting.