A SIMPLE METHOD TO MONITOR ONION BULB DORMANCY

Dormancy is an important factor in the storability of onion bulbs. It starts at about the time foliage is lodging (Komochi, 1990). Dormancy can be described as non-growth of sprout leaves, whereas sprouting is accelerated growth of sprout leaves. Sprout leaves of onion bulbs comprise a leaf sheath and a leaf blade. During initial sprout growth only the leaf blade is elongates, but not the leaf sheath (Bufler, unpublished; De Mason, 1990). Therefore, if sprout leaves with a defined leaf sheath length are monitored during dormancy, detection of an increase of the leaf-blade length will indicate initial sprout growth. Based on this principle, dormancy of a short-storing and a long-storing onion cultivar will be compared.