Physiology of Solanaceous Scion and Rootstock Seedlings for Grafting in Low Temperature Storage Conditions under Low Light Intensity

A potential application of low temperature storage is to establish techniques and conditions that increase the production of grafted vegetable seedlings for the planting season. If stored seedlings are provided with optimal light intensity and temperature, growth and development can be suppressed while not deteriorating seedling quality due to chilling injury. This will allow propagators to store seedlings, adjust the propagation schedule, and/or increase volume over time without increasing labor input. Finding storage light and temperature parameters on un-grafted seedlings would provide the foundational knowledge for further studies on the effect of low temperature storage on grafted seedlings. In this experiment performance of solanaceous scion and rootstock seedlings were evaluated during and after storage.  Cultivars included in the experiment were tomato (Solanum lycopersicum ‘Aloha’, ‘Conchita’, and ‘Durinta’, and S. lycopersicum x S. habrochaites ‘Maxifort’), pepper (Capsicum annuum ‘Double up’, ‘Red Bull’, and ‘Ti-135’), eggplant (S. melongena ‘Black Bell’, and ‘Black Shine’, S. melongena x S. sp. ‘Red Scorpion’), and Solanum torvum (‘TI-216’). Seedlings were stored for a period of 4 weeks at 10 °C under 5 µmol·m^-2·s^-1 photosynthetic photon flux (PPF). All cultivars maintained a visual quality score of 5 for day 0, 1, and 7. By day 14 all cultivars maintained a visual quality score of 5 ± 0, except for ‘Maxifort’ tomato which had a significantly different visual quality score of 4.7 ± 0.12. By day 21 all cultivars maintained a score of 5 ± 0, except for ‘Maxifort’ tomato, and ‘Black Shine’, and ‘Black Bell’ eggplant, demonstrating scores of 4.6 ± 0.13, 3.8 ± 0.08, and 3.4 ± 0.1, respectively. By day 28, the storage caused chilling damage on all genotypes, except for ‘Aloha’ and ‘Durinta’ tomato, which maintained a visual quality score of 5 ± 0. Chilling damage was most prominent on ‘Black Bell’ and ‘Black Shine’ eggplant leading to the lowest significantly different score of 3.0 ± 0. At the end of storage, the seedlings were moved to a greenhouse for further observation. Post storage observations taken at day 14 showed complete recovery, with all cultivars having a score of 5 ± 0. With most cultivars not exhibiting any damage until day 21 it can be recommended that solanaceous seedlings can be stored without loss of quality for 14 days. These preliminary results will be repeated to confirm the findings and used to test storability of grafted vegetable seedlings.