Variation in Chilling Sensitivity among Eight Dieffenbachia Cultivars

Abstract

This study evaluated chilling sensitivity of eight popular Dieffenbachia cultivars. Tissue culture liners were potted in 15-cm diameter pots using Vergro Container Mix A and grown in a shaded greenhouse under maximum photosynthetically active radiation of 285 μmol·m−2·s−1 for 5 months. After determining growth indices, the plants were chilled in walk-in coolers at 2, 7, or 12 °C for 6, 12, or 24 h. Chilled plants were placed back in the shaded greenhouse for chilling injury and growth evaluation. Visible symptoms of injury included chlorosis, necrosis, water-soaked patches on leaves, or complete wilting. In addition to leaf injury, stems of some cultivars chilled at 2 °C for 24 h became water-soaked at the base, which resulted in the death of either entire shoots or entire plants depending on cultivars. Leaf injury occurred in all cultivars chilled at 2 °C, except for ‘Panther’; and the longer the exposure at this temperature, the greater the injury. No visual injury was observed among plants chilled at 7 and 12 °C except ‘Tropic Honey’ that had 26% of leaves injured at 7 °C. Based on the percentage of injured leaves 12 days after chilling at 2 °C for 24 h, the sensitivity of the eight cultivars ranked as follows: Tropic Honey > Sterling > Carina ≥ Octopus > Camille > Camouflage > Star Bright > Panther. In addition to visual injury, plant growth was also affected by chilling during the subsequent 3 months of growth. All ‘Tropic Honey’ chilled at 2 °C died regardless of the tested chilling duration. Growth indices of all other cultivars except for ‘Panther’ chilled at 2 °C for 24 h significantly decreased compared with those of controls. ‘Camille’, ‘Camouflage’, ‘Carina’, and ‘Sterling’ also exhibited significant growth reduction after chilling at 2 °C for 12 h. This study showed that genetic variation in chilling sensitivity exists among cultivated Dieffenbachia. The identified chilling-tolerant cultivars could be used for breeding of new chilling-tolerant cultivars. The use of chilling-tolerant cultivars in production may reduce the chance of injury during heating outages and shipment.