Main content area

Spatial phytohormone profile of stored bulbs

Cools, K., Alamar, M. C., Terry, L. A., Chope, G. A.
Acta horticulturae 2016 no.1143 pp. 315-320
1-methylcyclopropene, abscisic acid, air, bulbs, dormancy, ethylene, maleic hydrazide, onions, postharvest treatment, sprouting, storage quality, temperature, zeatin
Early dormancy break and sprouting are major causes of quality loss in onion bulbs during postharvest storage. Plant growth regulators (PGRs) play a key role in governing dormancy. Different pre- and postharvest techniques (viz. maleic hydrazide, low temperature, and controlled atmosphere) are commercially used to extend storability of onions. Alternative postharvest treatments, such as continuous ethylene supplementation and 1-MCP have a positive effect on storability. However, the effect of these treatments on the spatial phytohormone distribution in onion bulbs has not been studied in detail and, as consequence, was studied herein. Onions cv. Sherpa were treated before curing (20°C for six weeks) with 10 µL L-1 ethylene, 1 µL L-1 1-MCP and 10 µL L-1 ethylene (simultaneously), or post-curing with 1 µL L-1 1-MCP and 10 µL L-1 ethylene for 24 h at 20°C. The bulbs were then stored in air at 1°C for 31 weeks. PGRs (viz. ABA, zeatin riboside [ZR] and isopentenyladenosine [IPA]) were analysed at each sampling point (0, 6, 19 and 31 weeks) for both top and bottom section of onion bulbs. Concentrations of ABA, IPA and ZR were significantly higher in the bottom section (45.8, 93.4 and 253 ng g-1 DW, respectively) compared with the top section of the onion bulbs (32.0, 47.3 and 86 ng g-1 DW, respectively). Moreover, although the treatment effect was not significant (p>0.05), average values for all three phytohormone studied tended to differ more between treatments in the bottom samples than in the top samples. Further experiments will need to be carried out to elucidate this trend.