Effect of vapor heat treatment on the symptom development of anthracnose in harvested ripe 'Irwin' mango.
Chan WenLi, Wu ChunTa
Author Affiliation: Department of Horticulture and Landscape Architecture, National Taiwan University, Taipei, Taiwan.
Journal of the Taiwan Society for Horticultural Science 58 : 103-116
Abstract : Mango anthracnose, caused by Colletotrichum gloeosporioides Penz. fungus, is a serious postharvest disease of mango; and it is also one of the major causes of fruit deterioration in 'Irwin' mango exported from Taiwan. Ripe 'Irwin' mango treated with standard vapor heat (VH) quarantine procedure (fruit core 46.5°C for 30 min) in an experimental VH equipment had less than 5.3% anthracnose incidence, significantly lower than the incidence of 66.7% for untreated control in 20 d of storage at 20°C. No anthracnose symptom was found on the conidia-inoculated and then VH treated fruit in 20 d, while the average diameter of the lesions was 24.2 mm on the inoculated fruit without VH treatment. However, when the inoculation was made after VH treatment, the result showed that the susceptibility of the fruit to anthracnose increased by VH treatment. When the quiescent C. gloeosporioides in vitro incubated on cellophane until appressorium-formation stage was either VH treated or not before being cultured in potato dextrose agar medium, the VH treated group had a mycelia regrowth percentage of only 6.8% while the other group, 94.4%. VH treatment apparently had a fungicidal effect on the quiescent conidia and prevented from their hypha regrowth in the culture medium. According to the regression curve of different lethal heat accumulation (above 45°C × time of treatment) of C. gloeosporioides in vitro incubated versus mycelium regrowth percentages, 5700°C.min of VH treatment would be adequate to reduce anthracnose decay of ripe 'Irwin' mango to less than 5%.