Low oxygen effect on Penicillium expansum mould in stored apple
Marta Mari, R. Gregori, M. Guidarelli and Bertolini
Abstracts Book, 6th International Postharvest symposium, 8-12 April 2009, Antalya, Turkey. 256 pages.
2009
บทคัดย่อ
P. expansum causing blue mould, is a serious postharvest pathogen in all growing pome fruit areas. Physical treatments, including storage atmosphere manipulation, have been developed to control postharvest fungal decay. The present study aimed to determine the influence of oxygen (O2) levels on growth of P. expansum (P37 strain). Pathogen enzymatic production at low O2 levels was also tested in in vitro trials by agarose diffusion assay. In in vitro trials, 100 ml of conidial suspension (103 conidia per ml) was spread on PDA dishes, stored for 30 days at 0°C with 0.7; 1.5; 3; 6 and 21 % O2. The concentration of carbon dioxide was 1 %. In in vivo trials, fruit were wounded and inoculated with 20 ml of a conidial suspension (103 conidia per ml) of P. expansum and stored with the same O2 concentrations for five months at 0°C plus 3 days at 20°C. No significant difference have been observed, within the different O2 concentrations, on P. expansum growth in vitro. The percentage of infected fruit was significantly greater at low O2 levels (0.7; 1.5; 3 %) than at 6 or 21%. However the dimensions of decay lesions, on apple exposed to 21 and 6% of O2, were significantly wider than those of apples stored at 0.7; 1.5; 3 % O2. In addition O2 levels deeply influenced the enzymatic activity. Polygalacturonases, proteases and amylases activities were increased by low O2 level (0.7%), whereas cellulases were reduced by the same O2 concentration. More investigations are required to better elucidate the interactions between pathogen-fruit-oxygen level and the role of the enzymes in pathogenicity.