Heat treatment effect on Cadophora luteo-olivacea of kiwifruit

Abstract

Heat treatment represents an alternative method to fungicides to control latent fruit pathogens, such as Cadophora luteo-olivacea of kiwifruit. This study reports the efficacy of different hot water (HW) and hot air (HA) treatments (45, 50, 55, 65, and 70°C with durations of 10, 15 or 20, 5 or 10, 5, and 3 min, respectively) on the conidial and mycelial growth of fungal isolates by in vitro assays. Both treatments at 70°C were the most effective in inhibiting conidial and mycelial growth of C. luteo-olivacea isolates. Treatment efficacy for HW and HA was on average 88% and 71%, respectively, on mycelial growth, and 100% and 91.3%, respectively, on conidial growth. A significant reduction of xylanase and pectinase enzyme activities of the isolates was detected after HW and HA treatment (70°C × 3 min). In most cases, both treatments showed a total reduction, sometimes varying with the target isolate. HA treatment was the most efficient treatment for reducing the skin pitting incidence in in vivo experiments, showing an average efficacy of 46.6%. Results show that heat treatments are effective against C. luteo-olivacea, but the main challenge will be to develop the optimal time × temperature combinations.