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Abstract Our study was designed to combat rot the fruits of cucurbits Surveying the natural disease incidence of the most cucumber and squash fruit rots occurrence in many locations of seven governorates (i.e. Beheira, Kafr El-Sheikh, Qalubiya, Ismailia, Sharkiya, Dakahliya and Giza) was performed. All laboratories, greenhouse and field experiments were carried out during autumn and spring of 2003 and 2004 seasons. The obtained results could be summariezed as following: 1- Surveying of cucumber and squash fruit diseases under greenhouse conditions indicated that, the fruit rot disease severity (DS) was obviously higher in 2003 than 2004 seasons with great variation between seasons and tested locations. 2- Isolation trials showed that 152 and 81 fungal isolates were isolated from rotted fruits of cucumber and squash respectively. These fungal isolates included Alternaria spp., B. cinerea, F. solani, Mucor spp., Penicillium spp., Pythium spp. and Sclerotinia sclerotiorum. 3- On cucumber fruits, the highest DS was incited by B. cinerea isolated from Ismaelia and Beheira and F. solani isolated from Beheira, Kafr El-Sheikh and Ismaelia whereas, B. cinerea isolated from Sharkia, Ismaelia and F. solani isolated from Ismaelia recorded the highest DS on the squash fruits. Summary 138 4- Disease severity on cucumber or squash fruits were increased with increasing inocula concentrations of the tested fruit rot pathogens from 1000 to 7000 spores/ml. The highest significant increase of DS was recorded when inocula concentration increased from 6000 to 7000 spores/ml (B. cinerea on cucumber and squash fruits) and F. solani (on cucumber fruits) mean while increasing inocula concentration of F. solani from 5000 to 6000 spores/ml caused the highest significant increase in DS comparing with any other rots. 5- Fruits of cucumber Heikal cultivar seemed to be the most resistant against infection with B. cinerea and F. solani followed by Delta Star, Shams, New Star, Fysal, Sinai I and Samar cultivars. 6- Disease severity caused by B. cinerea on cucumber fruits was significantly higher than DS caused by F. solani meanwhile, DS caused by both pathogens was significantly equal on squash fruits. Also, DS of both tested pathogens were increased as plant age and fruit age increased and it was significantly higher on the wounded than the unwounded cucumber or squash fruits. 7- Disease severity was significantly higher on fruits stored for 8 than those stored for 4 days. It was noticed that DS developed more slowly on cucumber fruits stored at lower temperature regimes (2, 5 and 7°C) than those stored at room temperature Summary 139 (24°C). At 24°C, DS caused by B. cinerea developed more quickly than that caused by F. solani. 8- Disease severity was significantly affected by CO2 concentrations and storage period. The lowest DS on cucumber fruits inoculated with B. cinerea or F. solani was recorded after 10 days of storage under conditions containing 10% CO2 concentration. 9- Exposing fruits to the UV-treatments at 280 and 320 nm resulted in significant decreases in DS. Applying the UVexposure under conditions of the present study could not be satisfactory practice for suppressing DS on the cucumber fruits. 10- All tested fungicides were effective in suppressing the growth of the tested fruit rot pathogens in vitro. Ronilan fungicide was the most effective one where it completely inhibited the growth of B. cinerea followed by Sumisclex fungicide. However, the fungicides Rovral, Sumisclex, Ronilan, and Tecto were the most effective ones respectively for inhibiting growth of F. solani. Inhibition of fungal growth (both tested pathoges) increased as the concentration of the tested fungicides increased. 11- Spraying cucumber or squash plants with any tested fungicide significantly decreased the fruit rot DS caused by B. cinerea or F. solani. The fungicides Copral and Teledor were the highly effective in controlling DS caused by B. cinerea Summary 140 whereas, Copral, Ridomil and Teledor were the best effective fungicides in controlling DS caused by F. solani on cucumber fruits. Also, Copral and Teledor were the best fungicides in decreasing DS caused by B. cinerea and F. solani on squah fruits. Increasing the fungicdal concentration decreased gradually the recorded DS on infected cucumber or squash fruits. 12- Spraying cucumber and squash plants with some resistance inducers significantly reduced the fruit rot DS on the harvested cucumber and squash fruits. On cucumber fruits, the lowest DS caused by B. cineria was recorded on fruits harvested from plants previously sprayed with KH2PO4, CaCl2 and Na2SO4, SA, OA Meanwhile, OA, KH2PO4 and SA were the best for controlling cucumber fruit rot DS caused by F. solani. In case of squash fruits, the lowest significant DS caused by B. cineria was recorded by SA followed by KH2PO4, OA, LiSO4, and Na2SO4 comparing with the untreated control. Also, the least DS of F. solani infections on squash fruits was recorded with OA followed by KH2PO4. 13- Spraying of cucumber and squash plants with some resistance inducers (Bion, SA, OA, KH2PO4 and CaCl2) induced changes in the electrophoresis of the soluble proteins in plant leaves. The number of protein bands was higher in leaves of treated plants than the untreated control. Comparing to the untreated cucumber leaves (control), 27 new protein Summary 141 bands with MW ranged between 51 and 39 kDa were appeared in leaves of treated cucumber plants. Similarly, 22 new bands with MW ranged between 55 and 47 kDa were detected in squash leaves. In general, the highest number of the new protein bands was detected in cucumber or squash leaves treated with Bion or salicylic acid (SA). 14- Spraying cucumber and squash plants with the most tested resistance inducers and fungicides resulted in conspicuous increases in the quantities of total and free phenols in fruits which inoculated with B. cinerea and F. solani comparing to fruits harvested from untreated plants (control treatment). In case of cucumber fruits, all tested treatments reduced the conjugated phenols while, Catechol, Bion and Ethephon (B. cinerea), Teledor, Copral and Catechol (F. solani) recorded the highest increases in quantities of total and free phenols in treated and infected cucumber fruits comparing with the untreated control. Similar trend was recorded concerning squash fruits. Spraying squash plants with Catechol recorded the highest quantity of free phenols while the highest quantity of total phenols was recorded with Copral fungicide treatment in case of B. cinerea infection. In case of F. solani infection, the highest quantities of free phenols were recorded with Ethephon and Teledor treatments. 15- Spraying cucumber and squash plants with the tested resistance inducers and fungicides affected the total amino Summary 142 acids content of harvested fruits, which inoculated with B. cinerea and/or F. solani. The highest increase in total amino acids in cucumber fruits harvested from plants sprayed with Teledor and Catechol and squash fruits harvested from plants sprayed with Calcium chloride (F. solani). On the other hand, spraying cucumber plants with Catechol, Teledor, Copral or Ethephon recorded the highest amounts of total amino acids in cucumber fruits inoculated with B. cinerea whereas, Teledor and Catechol were the best effective treatments in increasing total amino acids content in squash fruits inoculated with B. cinerea. 16- Spraying cucumber and squash plants with plant extracts or kombucha tea preparation significantly decreased DS of fruit rots caused by B. cinerea or F. solani. On cucumber fruits, marjoram extract was the most effective as it completely suppressed DS caused by B. cinerea followed by kombucha tea, ginger and garlic, henna and nigella. However, nigella, henna, marjoram and ginger preparations were the most effective where they decreased DS caused by F. solani, followed by thyme, kombusha tea, garlic and carnation, respectively comparing with the untreated control. As for squash fruits, henna, garlic, carnation and ginger preparations were the most effective for decreasing DS caused by B. cinerea followed by nigella, kombusha tea and marjoram whereas, the preparations of garlic, henna, ginger, nigella, Summary 143 carnation and thyme were the most effective against fruit rot caused by F. solani. 17- Using any of the tested plant extracts or kombusha tea greatly decreased the activity of PME enzyme in cucumber fruits inoculated with B. cinerea or F. solani comparing to the untreated control. In cucumber fruits inoculated with B. cinerea, ginger extract was the most effective for reducing PME activity followed by marjoram, nigella, garlic, kombucha, carnation, henna and thyme, respectively whereas, ginger extract still the most effective for decreasing PME activity in fruits inoculated with F. solani, followed by nigella, marjoram, kombucha, garlic, thyme, carnation and henna, respectively. In squash fruits inoculated with B. cinerea, kombucha tea and nigella were the most effective for reducing PME activity followed by marjoram, ginger, garlic, carnation, henna and thyme particularly comparing to the untreated control. However, in fruits inoculated with F. solani, nigella and thyme extracts were the most effective and completely suppressed PME activity followed by garlic, kombucha, ginger, marjoram, henna and carnation, respectively. 18- Spraying cucumber and squash plants with any of the tested preparation (plant extracts or kombusha) decreased activity of the polygalacturonase (PG) enzyme in their fruits inoculated with B. cinerea or F. solani comparing to the inoculated fruits harvested from the untreated plants. In general, garlic extract Summary 144 caused the highest reduction in activity of PG followed by kombucha, marjoram, nigella, carnation, henna, thyme and ginger extracts, respectively in fruits inoculated with B. cinerea. However, thyme extract caused the highest decrease in PG activity in inoculated fruits with F. solani followed by nigella extract, kombucha, henna, marjoram, ginger, garlic and carnation, respectively. 19- The activity of polyphenoloxidase (PPO) enzyme was higher in cucumber and squash fruits harvested fron plants previously sprayed with any of the tested plant extracts or kombusha tea after inoculation with B. cinerea or F. solani comparing to inoculated fruits harvested from control treatment (untreated). In fruits of cucumber, the highest PPO enzyme activity was recorded with pre-harvest treatment with nigella extract (B. cinerea) and marjoram and nigella extracts (F. solani). As for squash fruits, the highest activity of PPO enzyme was recorded in fruits harvested from plants formerly sprayed with with nigella extract and kombusha followed by thyme, henna and carnation extracts respectively (B. cinerea) and marjoram, henna and carnation extracts (F. solani). 20- As for the activity of peroxidase (PRO) enzyme in cucumber fruits under stress of infection with the tested fruit rot pathogens, the highest PRO activity was recorded in fruits harvested from cucumber plants previously sprayed with henna followed by ginger and kombusha tea respectively (B. cinerea)and henna, kombusha and marjoram extract, respectively (F. solani). In squash fruits inoculated with B. cinerea, the activity of PRO enzyme was higher in fruits harvested from plants that were pre-sprayed with henna and kombusha tea, respectively. In case of squash fruits inoculated with F. solani, the highest PRO activity was recorded in fruits harvested from plants treated with nigella extract followed by henna. |