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Abstract Potato (Solanum tuberosum L.) is considered one of the most important vegetable crops in Egypt and in the world, as well as its importance in local fresh consumption and use in food processing. Potato plants are suffering from many diseases during all stages of growth. Fusarium wilt, black scurf and stem canker and root-knot nematode are the most popular diseases, which cause considerable losses in tuber yield especially in their (disease complex). Results obtained from the present investigation could be summarized as follows: 1. According to potato growing areas, there is a variation in percentage of occurrence of Rhizoctonia solani and Fusarium spp. in four governorates. The highest percentage of R. solani was recorded in Kafer El-Zayat (68.3%), while the highest percentage of Fusarium spp. (80.2%) was found in Berkat El-Sabaa. 2. A survey of root-knot nematode Meloidogyne spp. was conducted in five locations of four different governorates. Sadat city, Kafer El-Zayat, Kom Hamada, Wadi El-Natron and Giza were the highest percentage of nematode occurrence (100%), while the highest population density achieved 660.00 larvae / 250 g soil in Giza. 123 Summary 3. Culture filtrates of nine Fusarium spp. isolates reduced mixed population of Meloidogyne spp. (M. javanica and M. incognita) egg hatching under laboratory conditions. The greatest egg hatching inhibition was recorded by Berkat El-Sabaa isolate, while the least inhibition was recorded by Sadat city isolate. 4. Culture filtrates of nine Rhizoctonia solani isolates inhibited mixed population of Meloidogyne spp. egg hatching under laboratory conditions. The greatest egg hatching reduction was recorded by Tanta isolate, while the least reduction was recorded by Shibin El-Kom isolate. 5. Culture filtrates of nine Fusarium spp. isolates were effective in reducing mixed Meloidogyne spp. larvae mobility. The greatest larvae immobility was achieved by Berkat El-Saba isolate, while the least one due to Sadat city isolate. 6. Culture filtrates of nine R. solani isolates were effective in reducing mixed Meloidogyne spp. larvae mobility. The greatest larvae immobility was recorded by Tanta isolate, while the least one was recorded by Shibin El-Kom isolate. 7. All tested culture filtrates of biocontrol agents reduced mixed Meloidogyne spp. egg hatching. The best isolate was Bacillus megaterium, while the least one was Trichoderma harzianum. 124 Summary 8. All tested culture filtrates of biocontrol agents reduced mixed Meloidogyne spp. larvae mobility. The best isolate was B. megaterium, while the least one was T. harzianum. 9. All tested biocontrol agents were effective against pathogenic Fusarium spp. isolates and inhibited the fungal linear growth. Trichoderma koningii revealed the most effective fungal bioagents, while Bacillus megaterium was the most effective bacteria under laboratory conditions. 10. All tested biocontrol agents were effective against pathogenic Rhizoctonia solani isolates and inhibited the fungal linear growth. Trichoderma koningii revealed the most effective fungal bioagents, while Bacillus megaterium was the most effective bacteria under laboratory conditions. 11. All tested concentrations of marjoram and thyme wastes reduced egg hatching of mixed Meloidogyne spp. under laboratory conditions. The highest reduction was observed by 1/10 concentrate of the two wastes. 12. Different concentrations of marjoram and thyme wastes reduced larvae mobility of mixed Meloidogyne spp. under laboratory conditions. The highest reduction was observed by 1/10 concentrate of the two wastes. 125 Summary 13. Different concentrations of marjoram waste were effective against pathogenic Fusarium spp. isolates and inhibited the fungal linear growth under laboratory conditions. The highest percentage of reduction (87.77%) observed by 1/10 concentrate, while the least one (34.44%) observed by 1/100 concentrate. 14. Different concentrations of thyme waste were effective against pathogenic Fusarium spp. isolates and inhibited the fungal linear growth under laboratory conditions. The highest percentage of reduction (87.77%) observed by 1/10 concentrate, while the least one (24.44%) observed by 1/100 concentrate. 15. All tested concentrations of marjoram waste reduced the linear growth of Rhizoctonia solani isolates under lab conditions. The concentrate 1/10 gave the best reduction (84.44%), while the concentrate 1/100 gave the least reduction (31.11%). 16. All tested concentrations of thyme waste reduced the linear growth of Rhizoctonia solani isolates under lab conditions. The concentrate 1/10 gave the best reduction (86.66%), while the concentrate 1/100 gave the least reduction (23.33%). 17. Inoculation of root-knot nematode mixed population of Meloidogyne spp. alone or with Rhizoctonia solani to the soil infested with Fusarium oxysporum significantly increased Fusarium wilt disease incidence under greenhouse conditions. 126 Summary 18. Inoculation of root-knot nematode mixed Meloidogyne spp. alone or with F. oxysporum to the soil infested with R. solani increased black scurf and stem canker disease incidence in pots. 19. Inoculation of F. oxysporum alone or with R. solani reduced reproduction factor and all related parameters of mixed Meloidogyne spp. in pots. 20. Interaction between root-knot nematode, R. solani and F. oxysporum was more effective in reducing potato plants growth parameter compared with any individual pathogen. 21. Under greenhouse conditions; application of Trichoderma koningii and Bacillus megaterium alone or in combination seven days earlier than soil infestation with F. oxysporum significantly reduced Fusarium wilt disease incidence. 22. Under greenhouse conditions; application of Trichoderma koningii and Bacillus megaterium alone or in combination seven days earlier than soil infestation with R. solani significantly reduced black scurf and stem canker disease incidence. 23. Application of the biocontrol agents T. koningii and Bacillus megaterium alone or in combination significantly reduced reproduction factor and all related parameters of mixed Meloidogyne spp. in pots. 24. Biocontrol agent applications to the soil significantly improved plant growth parameters. 127 Summary 25. Application of the endophyte Fusarium oxysporum one week before soil infestation with F. oxysporum significantly reduced Fusarium wilt disease incidence. 26. Application of the endophyte Fusarium oxysporum one week before soil infestation with R. solani significantly reduced black scurf and stem canker disease incidence. 27. The endophyte F. oxysporum significantly reduced reproduction factor and nematode parameters on potato plants. 28. The endophyte F. oxysporum significantly improved plant growth parameters. 29. Marjoram and thyme wastes were effective in reducing Fusarium wilt when they were applied to the soil at the time of planting. 30. Marjoram and thyme wastes were effective in reducing black scurf and stem canker by application to the soil at the time of planting. 31. Application of marjoram and thyme wastes at the same time of planting significantly inhibited the reproduction factor and nematode parameters. 32. Application of marjoram and thyme wastes to the soil significantly increased plant growth parameters. |