BULB TISSUE COLD-TOLERANCE SENSITIVITY DIFFERENCES IN LILIUM LONGIFLORUM 'NELLIE WHITE' AND L. FORMOSANUM
As part of a breeding objective for selection and development of winter-hardy (USDA Z3-4), seed-propagated interspecific lily hybrids, this research focuses on the identification of cold-sensitive levels of lily bulb tissue(s). The objective of this experiment was to test two cold-sensitive Lilium spp. for tissue sensitivity to and damage by freezing temperatures. Bulbs of L. longiflorum Nellie White and a L. formosanum hybrid population were acclimated at 2°C for 1,000 hours. In a separate experiment, Nellie White bulbs were also acclimated at 2°C for 2,000 h. Cold tolerance was assessed using laboratory freezing tests at 0, -2, -6, -8, -10, -12°C with varying ramp time periods and a 2 hour soak time in a programmable freezer. Lethal temperatures at which 50% kill occurred (LT50) of all bulb tissues (basal plate, roots, mother scales, daughter scales, meristem, pre-formed leaves), reduction and quantitative regrowth data (leaf, root numbers; shoot length) were determined for dissected bulbs tissue(s) after freezing. Significant changes in the interaction of genotype × temperature were detected. The LT50=-6°C for all structures of Nellie White bulbs (both 1,000 and 2,000 h) and roots of L. formosanum whereas an LT50=-8°C was found for L. formosanum mother and daughter scales, leaves, meristems, and basal plates. Cooling for 1,000 h resulted in significant regrowth differences for leaf number and shoot length of Nellie White between -6 and -8°C. However, after 2,000 hours cooling the number of leaves and shoot length differed significantly between -2 and -6°C for Nellie White. TTC tests did not correspond to laboratory freezing LT50s and had insufficient or variable amounts that were difficult to detect. As a result, laboratory freezing and regrowth tests provide more substantive data for use in determining cold tolerance in geophytic Lilium.
Fang Du, , Anderson, N.O. and Yiping Xia, (2013). BULB TISSUE COLD-TOLERANCE SENSITIVITY DIFFERENCES IN LILIUM LONGIFLORUM 'NELLIE WHITE' AND L. FORMOSANUM. Acta Hortic. 1002, 123-129
bulb tissue, freezing injury, Lilium