Efficacy of guava and mangosteen extracts in reducing soft rot (Pectobacterium carotovorum) in harvested Chinese cabbage
2018
Barbin, K. B. | Secretaria, L. B. | Bayogan, E. R. V. | Lacap, A. T. | Ekman, J. H.
The effect of mature guava leaf and mangosteen rind extracts was evaluated in soft rot (Pectobacterium carotovorum)-inoculated butt-ends of Chinese cabbage heads. Chemical extraction (with methanol and ethanol) exhibited higher antibacterial properties in the bioassay compared to the mechanically produced extracts. The inhibition zones observed with five concentrations (100, 250, 500, 750 and 1000 µg mL-1) of guava leaf and mangosteen rind extracts did not vary but were significantly better than distilled water. Newly-trimmed Chinese cabbage heads were inoculated with the soft rot organism 24, 48 and 72 h followed by air-drying for 30 min before treatment with 10% alum (positive control); distilled water (negative control); and extracts from mature guava leaf (1000 µg mL-1) or mangosteen rind (500 µL L-1). In the bioassay, the mangosteen rind extract exhibited a greater diameter of inhibition than the guava extract but this was lesser in vitro. The two extracts very slightly extended shelf life of heads held under ambient conditions (26.2±0.30°C, 84.8±2.0%RH) by one day. On the other hand, the 10% alum treatment extended shelf life to twice that of the control. Delaying inoculation on butt-ends trimmed 72 h earlier delayed onset of disease by one day. This study confirms efficacy of 10% alum in reducing soft rot in Chinese cabbage butt-ends. Further assessment is needed to evaluate other concentrations of the two plant extracts.
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