This work was carried out during two successive seasons (2016 and 2017) on cucumber fruits from a plastic greenhouse and from open field cultivation in El Gharbeia and El Giza Governorates, Egypt. Isolation trials from spoilage fruit samples of plastic greenhouse cultivation recorded high frequency of Alternaria tenusinium, Fusarium spp. and Pleospora alli. The most common fungi of rotten cucumber fruits from an open field were Galactomyces spp. and Fusarium spp. Pathogenicity tests proved that, Fusarium solani from El-Gharbeia followed by A. tenusinium from El-Giza were the most frequent isolates responsible for rot of cucumber fruits from plastic greenhouse cultivation. Moreover, the most frequent isolates causing postharvest disease of cucumber fruits of the open field were Galactomyces candidium from El-Giza followed by Geotrichum sp. and F. fujikuroi from El-Gharbeia Governorates, respectively. This is the first report of several fungi causing postharvest fruit rot disease of cucumber i.e., G. candidium, Geotrichum sp., A. tenusinium, P. alli and Fusarium spp. (F. fujikuroi, F. verticiolides, F. solani, F. geraminearium and Fusarium incarnatum). Fungal isolates were identified according to cultural, morphological and molecular characterization based on sequencing of internal transcribed spacer1 (ITS1). All the ITS nucleotide sequences of fungi were applied and conserved in GenBank.
The virulent isolates of Colletotrichum capsici and Alternaria alternata produced more cellulolytic enzymes viz., C1 and Cxin vitro than the avirulent ones and the activity of these enzymes increased with the increase in age of culture. The virulent isolates of C. capsici and A. alternata produced more pectinolytic enzymes (macerating enzymes, pectin methyl esterase and endo polygalacturonase) than the avirulent ones. All the pectinolytic enzymes were highly active in 10-day-old culture and the activities decreased with the increase of culture age. Whereas the activity of enzymes produced by avirulent isolate of pathogens did not decrease and these enzyme activities increased with the increase in the age of culture. These pathogens also produced nonspecific toxic metabolites in culture filtrate which reduced seed germination, root length, shoot length and vigour index of the seedlings of chilli, rice, mungbean, maize, cotton, groundnut, okra, egg plant, cucumber and tomato. The toxins of the pathogens reduced seed germination and caused mortality of chilli seedlings in pot culture. The toxins also produced phytotoxic symptoms in the treated ripe and green chilli fruits and leaves.
The inhibitory properties of the ethanolic and methanolic leaf extracts of Vernonia amygdalina and Cola acuminata on the fungal pathogens isolated from infected tomato fruits were investigated. The pathogens were Fusarium moniliformes and Rhizopus stolonifer. Various concentrations of the extracts ranging from 10, 20, 30, 40, 50, 60, 70, 80, 90 and 100% were separately added to PDA media. The fungal pathogens were separately inoculated into the media and incubated for seven days. Antifungal effects of these extracts on the mycelia growth of the pathogens were significant at P<0.05 for all treatments at higher concentrations. At 10-50% concentration, ethanolic and methanolic extracts of Vernonia amygdalina and Cola acuminata had no significant effect on the mycelia growth of Fusarium moniliformes and Rhizopus stolonifer after seven days observation period. At 60-100% concentrations, the two pathogens were completely inhibited by ethanolic extracts of Vernonia amygdalina and Cola acuminata. Methanolic extracts of Vernonia amygdalina and Cola acuminata inhibited completely Fusarium moniliformes and Rhizopus stolonifer at 80-100% concentrations. The in vitro inhibitory effects of these extracts at higher concentrations indicated that they can be used for the control of tomato fruit rot. It may be necessary to use them in prolonging the shelf-life of fresh tomato fruit and some other fruits.
During the cold storage of sweet cherry, severe losses can occur due to the water loss, phytopathogenic fungi and physiological disorders. The aim of this research was to assess the effects of treatments with NAA (α-naphthaleneacetic acid), BA (6-benzyladenine), and GA3 (gibberellic acid) on fruit quality at harvest and after 21 days of storage under two regimes, including 0°C, RH (relative humidity) 90% and 3°C, RH 70%, and after additional shelf life exposure. Sweet cherry cultivars – ‘Summit’, ‘Kordia’ and ‘Regina’ – were treated with bioregulators at the end of flowering. NAA significantly increased the fruit weight at harvest compared to the control in all cultivars assessed. BA stimulated the fruit growth in ‘Kordia’ and ‘Regina’, while it was ineffective in ‘Summit’. GA3 caused significant increase in fruit weight by 8.3% in ‘Kordia’ only. Moreover, BA and GA3 induced a higher firmness of fruits at harvest. Weight loss of fruits during storage at 0°C, RH 90%, was increased with NAA and reduced with GA3 in ‘Regina’ only. BA and GA3 reduced the weight loss of sweet cherry fruits stored at 3°C, RH 70%. Bioregulator treatments increased TA (titratable acidity) in fruits at harvest, while the effects on TA during storage were variable depending on the cultivar. ‘Summit’ had the highest sensitivity to storage fruit rot. BA and GA3 decreased the disease occurrence on fruits stored at 0°C in ‘Summit’ and ‘Kordia’.
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