MONITORING STUDIES IN ONION (ALLIUM-CEPA L) SEEDS RETRIEVED FROM STORAGE AT -20-DEGREES-C AND -180-DEGREES-C

Seeds of two onion (Allium cepa L.) cultivars Puss Red (PR) and Puss W hite Flat (PWF) were studied for their ability to produce normal plant s after storage for 18 months at -20 degrees C and -180 degrees C (vap our phase of liquid nitrogen). These seeds maintained uniform speed, v iability, vigour and low frequency of aberrations in comparison to con trols maintained at room temperature (RT) where significant decline in viability occurred. A marginally higher level of aberrations occured at -20 degrees C than at -180 degrees C. Storage under cryopreservatio n prevented loss of vigour and also reduced aberration frequencies. Th erefore, although negative temperatures provide good conditions for co nservation, vapour phase of liquid nitrogen may be preferable over -20 degrees C for extended storage periods.