شروین هادیان

Citrus green mold, Penicillium digitatum is one of the most important postharvest diseases. Continuous application of chemical pesticides has serious long term effects on human health and environmental pollution that may result in emergence of resistance in pathogenic strains. In this study, antifungal activity of different concentrations (100, 200, 300, 400ppm) of four medicine plants essences including Thymus vulgaris, Cuminum cyminum,Allium sativum and Aloe vera collected from Ghorogh area of Golestan provience was evaluated. Essences were prepared by the steam distillation water using Clevenger apparatus. The main constituents' essences having the most antagonistic activity were analyzed by GC / MS. Antagonistic activity of bacteria isolated from orange epithelium including Bacillus, Pseudomonas sp., and Streptomyces sp. against Penicillium digitatum was also investigated in a completely randomized factorial model. The maximum percent inhibition (99.95%) was observed by the thyme plant essence at 400 ppm concentration. Regression analysis of the effects of essences showed that by increasing the essences concentration, its inhibitory effect on fungi increased. Based on the results, thyme essence with having the important constituents of essences (carvacrol - 45.5%), (alpha-terpineol - 22.9%) and (endo - borneol 14.3%) had the highest inhibitory effect (22.3 mmol) against penicillium. Among 23 bacterial isolates, one of them, H7, had the highest inhibitory effect on penicillium. Using PCR amplification and DNA sequencing of 16S rRNA gene, it was identified as Bacillus cereus. Thus, thyme essence and Bacillus cereus (H7) are an appropriate substitutions to chemical control of orange postharvest diseases caused by Penicillium digitatum.

Using natural plant products has become more important as viable alternatives to control postharvest diseases. The effect of four essential oils of medicine plants including Thymus vulgaris, Cuminum cyminum,Allium sativum and Aloe vera were tested (100, 200, 300, 400ppm) in vitro and in vivo (200,300,400 ppm) for their fungal inhibitory percentage and antagonistic properties against Penicillium digitatum. Plant essential oil extracted by hydro distillation using a Clevenger-type, and minimal inhibition concentrations (MIC) was determined using agar dilution method. In vitro inhibitory effects of the plant extracts showed maximum percent inhibition (99.95%) by thyme extract, which also had the best MIC value against P. digitatum. GC-MS analysis of the thyme oils extract led to the identification of 22 different components which carvacrol (2.88%), 60.18% thymol (60.18%), linalool (4.22%), γ-terpinene (6.39%) were found to be the main constituents in T. vulgaris. Thyme essential oil inoculated into wounds with the pathogen stimulated the orange to increase production of phenol compound, catalase and peroxidase activity. Thus, different concentrations of the thyme essential oil are effective on controlling the producing agent of the green mold fungus significantly, and induce resistance to orange by effect on defense enzyme.