MORPHOLOGICAL-CHANGES IN TUBER BUDS DURING DORMANCY AND INITIAL SPROUT GROWTH OF SEED POTATOES

Potato tuber dormancy is usually defined as lasting from tuber initiation until a sprout of 2 mm long has been formed under storage conditions optimal for sprouting. We tried to find out whether there is a period during which buds of seed tubers do not grow and whether different batches of seed take the same time to grow sprouts 2 mm long. We measured changes in number of leaf primordia and length of tuber buds of cvs Diamant and Desiree over two years. After early haulm pulling, buds did not grow for at least 60 days ('Diamant') or 95 days ('Desiree'). Buds in both cultivars and two tuber weights of 'Diamant' took about 20 days from the estimated onset of sprouting to grow 2 mm long. We question whether this period is always similar and thus whether the moment sprouts 2 mm long have formed is a good criterion for the end of dormancy.