DORMANCY

Dormancy is a state in which tubers will not sprout even when placed under conditions ideal for sprout growth (18-20ºC, 90% RH and darkness). Duration of dormancy is normally counted from the date of harvest. Based on the dormancy duration from the date of harvesting (it is assumed that harvesting is done 10-15 days after dehaulming) in the plains, Indian potato cultivars can be divided into three categories: Short dormancy: < 6 weeks.  e.g. Kufri Bahar; Medium dormancy: 6-8 weeks.  e.g. Kufri Jyoti & Long dormancy: >8 weeks.  e.g. Kufri Sindhuri. Even within a cultivar, dormancy duration can be affected by growth conditions and tuber weight. Dormancy duration is not related to the crop duration of a cultivar. In other words, it is not necessary that a late cultivar should have long dormancy. 

Soil and environmental conditions during crop growth have a strong influence on the dormancy duration. Cold and wet weather is known to increase the dormancy duration while dry and warm weather reduces it. Potatoes grown under short-day conditions (plains) have shorter dormancy duration than those grown under long-day conditions (hills). For example the dormancy duration in Kufri Jyoti, Kufri Chipsona-1 and Kufri Chipsona-2 was 55, 47 and 40 days, respectively when grown in the northern plains under short day conditions and 126, 84 and 91 days, respectively when grown in the northern hills under long day conditions. Season (year) to season variation in the duration of dormancy can also be considerable due to variation in the environmental conditions during crop growth.

Storage temperature has a strong influence on the dormancy duration. Higher storage temperature hastens dormancy release, while storage at a temperature of 4ºC and below prolongs dormancy by preventing sprout growth. Exposure to light during storage also affects dormancy duration but its effect is much less compared to temperature effect. RH in the storage atmosphere has very little effect on dormancy duration. Concentration of gases in the storage atmosphere also affects dormancy duration. Lower concentration of oxygen (O₂) and higher concentration of carbon-di-oxide (CO₂) hasten the release of dormancy and stimulate sprout growth.