Chinese Cabbage Cultivars Vary in Susceptibility to Postharvest Development of Black Speck
The physiological disorder black speck is one of the major causes of postharvest losses of Chinese cabbage in California. Mature heads from 16 cultivars from three trials were evaluated in 1995 and 1996. No black speck was observed at harvest. A sequential combination of postharvest conditions reported to induce black speck (storage at 0°C for 1-2 weeks, exposure to 5 ppm ethylene for 7 days at 5°C, and transfer to 15°C for 3 to 7 days) were applied to 20-30 heads per cultivar per harvest. The more tolerant cultivars showed a low severity score, low incidence, and/or low percentage of affected leaves; conversely, susceptible cultivars has high score for severity, a high percentage of heads affected and/or a high percentage of leaves affected. A black speck index was calculated based on the severity score and percent of leaves affected. Results to date indicate that cultivars China Express, China Flash, XPH-5575, Gold Leaf, and Monument developed less black speck and that cultivars Early Meeho, Pride #2, FMX-425, Optiko, and Blue were the most susceptible. Another six cultivars (You Needs, SCC9206, Green Sweet, WR-70, PSR 4894, and Tango) had intermediate black speck development. Screening Chinese cabbage cultivars under black speck-inducing conditions should be useful way to reduce this postharvest disorder.