this problem is due to exposure of the potato tubers to light and is common in varieties whose tuber formation is shallow. this can occur during tuber formation in soil, and storage in exposed light. This problem can be avoided i) by using either the deep tuber setting varieties or ii) by by making high hills to avoid tuber exposure to light. Some timers cracking of soil during drought conditions also expose the tuber to sun light. To avoid storage greening, the tubers should be harvested at proper time as immature tubers has high level of solanine than the mature tubers.

go for earthing up 

The practice of earthing or dirting should be coincided with a last cultivation. Cultivation is angled to throw dirt toward and on top of the row.

Then If straw is available the use of mulching will help and not permit rainsplashed diseases to be so bad.  If potatoes are irrigated use of drip will ensure bactierial disease are less.  For best potato yields they need early Phosphorus and plenty of potassium at flower into bulking.

The mulching with reduce moisture fluctuations of the soil and temperature bringing a better environment to reduce cracking.

Try to cover the tubers that appeared to the light with soil 

Greening is due to the exposure of tubers to the direct sunlight caused by increased production of solanine (glycoalkalod). Greening can be occurred in the production field as well as in storage. Therefore, try to protect the tubers from  direct sunlight. This can be achieved by increasing the hills during cultivation and protecting the tubers from sunlight exposure in the storage (dark storage). Try to avoid cracking of soils especially during drought conditions, thus cracks expose tuber to sunlight.

Besides, harvest potato at proper maturity stage, since immature tubers are more liable to greening than the matured once.

I agree with the above.    Consuming too much solanine, one of a number of glycoalkaloids, can lead to death.   There is a famous case of a potato breeder who had a meal of green potatoes with dire consequences (he died).

I also agree with the above answers. production of alpha solanine, is the reason for tuber greening. This happens following tuber exposure to light either while the crop is in the field or at storage place. Earthening up is one of the best option to tackle this problem. In storage better to avoid light entery to the storage. There could be varietal difference in sensitivity. Never consume green tubers as they can lead to death.