الفهرس 
Postharvest Treatment of Citrus Fruits with Some Organic and Inorganic Compounds for Protection against Rot-Inducing OrganismsOnly 14 pages are availabe for public view
 |  | from | 77 |  |  |
| | | from | 77 | | |
Abstract
This study was conducted at Plant Pathology Department, Faculty of Agriculture, Alexandria University, aims to study the effect of fungicides alternatives on postharvest diseases of Murcott mandarin fruits and include potassium silicate and chitosan at different concentrations and their effect on physico-chemical characteristics and reduce decay of fruits, to achieve this study, several steps were followed can be summarized as follows:
1- Samples of diseased citrus fruits (Valencia, Navel orange and Murcott mandarin) showed green mould symptoms were collected from field at harvest, packing house and market in El-Beheira and Alexandria Governorate during the 2014 and 2015 season.
2- Isolation, purification of the causal agent were performed and identification of fungal isolates were carried out according to microscopic morphological. Twelve isolates of Penicillium digitatum from fruits were isolated.
3- Pathogenicity test for twelve tested isolates of P. digitatum were examined using Valencia and Murcott mandarin fruits at 23±2ᵒC, results of pathogenicity tests were, as the following:
• Fungal isolates were grown on the tested Valencia and Murcott mandarin fruits, after 7 days.
• P. digitatum had different pathogenic capabilities on Murcott mandarin and Valencia fruits where isolate No. 1, 2, 3, 4, 5 and 6 was highly pathogenic, while isolates No. 7, 8 and 9 was moderate pathogenic, as well as isolate No. 10,11 and 12 was least pathogenic.
• The Murcott mandarin was the most susceptible as green mould developed with artificial infection covered 36.82% of the fruit surface. Meanwhile, Valencia orange exhibited lowest susceptibility as green mould developed with artificial inoculation covered 24.55% of the fruit surface.
4- Potassium silicate at 60, 90, 150, 210 mM and chitosan at 2, 4, 6 g /l were showed a significant effect in inhibition of growth virulent of P. digitatum isolate in vitro, while potassium silicate at 60mM and chitosan at 2 g / l showed an insignificant effect.
5- Potassium silicate at 90,150 mM and chitosan at 4,6 g/l induced resistance of Murcott mandarin fruits showed a significant inhibition against the green mould caused by P. digitatum on Murcott mandarin fruits.
6- Effect of the tested compounds on the defense related enzyme activities of peroxidase (POD) and catalase (CAT) were determined on Murcott mandarin at 0h, 12h, 24h, 72h, 168h after inoculation with virulent isolate of P. digitatum
There was an increase in the enzyme activity at all concentrations of Potassium silicate (Ksi) at 90 and150 mM, and Chitosan( Chit) at 4 and 6 g/l.
• The highest of POD activity is at 72 h, treatment with potassium silicate at 90 mM and Chitosan at 4 g/l was the most effective as increased POD.
• The general trend of the data indicated an increase in the enzyme activity till 72 h, treatment with Ksi at 150 mM was the most effective as increased CAT for Murcott mandarin.