ORIENTAL HYBRID LILY CULTIVARS VARY IN SUSCEPTIBILITY TO UPPER LEAF NECROSIS

Abstract

Upper leaf necrosis (ULN) in Oriental hybrid lilies (Lilium L.), commonly observed as leaf tip burn, is a calcium (Ca) deficiency disorder. In this study, we compared the susceptibility of four cultivars, 'Star Gazer', 'Acapulco', 'Sissi', and 'Alliance', and investigated some calcium nutrition characteristics that may contribute to ULN susceptibility. We found that 'Star Gazer' and 'Acapulco' are susceptible cultivars, 'Sissi' and 'Alliance' are not, and 'Star Gazer' suffers from more severe ULN than 'Acapulco'. At planting, the Ca concentration in the bulb scales was similar in the four cultivars, approximately 0.03% DW. However, the susceptible cultivars had lower initial Ca concentration in leaf primordia than the non-susceptible ones, and the most susceptible 'Star Gazer' had the lowest. Thirty days after planting, leaf Ca concentration was highest (1.01%) in 'Acapulco', with no difference among the other three cultivars (in the range of 0.54-0.65%). During this 30-day period, the net Ca gain from the media in 'Acapulco' was 43 mg/plant, about 60% more than the other cultivars. The results agreed with the observation that 'Acapulco' had the highest transpiration rate. Shoot growth rate in the most susceptible period for ULN (30-40 days after planting) was approximately 0.18 g.day-1 for 'Star Gazer', 'Acapulco', and 'Sissi', but only 0.09 g.day-1 for 'Alliance'. Although the low initial Ca concentration in leaf primordia may play a role, it is difficult to isolate a single characteristic to explain the observed cultivar variation to ULN in Oriental hybrid lilies.