Splitting in Radish – Does Preharvest Environment Influence the Response to Postharvest Handling?

Splitting in radish (Raphanus sativus) hypocotyls is a problem for growers which occurs both pre- and postharvest. Experiment 1 investigated the effects of timing of irrigation application on splitting and the hypocotyl water content at harvest. Experiment 2 investigated the effects of hypocotyl water content on susceptibility to splitting postharvest. In Experiment 1 R. sativus ‘Rudi’ plants were glasshouse grown, the three treatments were watered for seven days then given two irrigation treatment periods of 10 days each: on-going irrigation (W/W), period of no irrigation followed by irrigation (D/W), and period of irrigation followed by no irrigation (W/D). At harvest the D/W treatment produced fewer splits than the W/D and W/W treatments (P<0.001) suggesting a dry period mid-growth results in less splitting. At harvest, treatment W/D had a significantly (P<0.001) lower hypocotyl water content on average than W/W and D/W. This suggests that irrigation in the final 10 days prior to harvest determines hypocotyl water content at harvest. In Experiment 2, hypocotyls at a range of water contents between 93 and 97% were tested for susceptibility to splitting as a result of postharvest mechanical damage using impact and puncture tests. Radish hypocotyl water content was found to be negatively correlated with puncture force and an increase in the number of radishes which split after dropping was observed at hypocotyl water contents above 96.5%. In conclusion, the water content of the growing medium during growth influences splitting at harvest, the water content of the growing medium prior to harvest affects the water content of the hypocotyl at harvest and radishes are more susceptible to splitting postharvest from dropping and puncture at high hypocotyl water contents.