الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
 |  | from | 119 |  |  |
| | | from | 119 | | |
Abstract
White rot of garlic caused by the soil inhibiting fungus Sclerotium cepivorum Berk is a world-wide disease. It affect greatly productively of garlic in Upper Egypt. Many attempts have been done to control the disease using crop rotation, culture practices and resistance varieties, but their effectiveness are still very limited.
The current work was planned to study the induction of resistance and biological control.
Results of this work can be summarized in the following:
1. Forty-three isolates of S.cepivorum obtained from different localities of El-Minia, Assiut and Sohag Governorates were able to infected Chinese garlic cultivar and produced typical symptoms of white rot. The pathogenic potentialities of the tested isolates from weakly to severe. Isolates No. 18, 42, 7 and 13 caused the highest percentage of infection, however isolates No. 20 and 27 caused the lowest percentage of infection.
2. The tested isolates of the pathogen produced white mycelium, small and very small black sclerotia on PDA medium. Sclerotia produced by isolates were different in their population density.
3. The Protein of six isolates of S. cepivorum were compared by polyacrylamide gel electrophoresis (PAGE) and sodium dodecyel sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Protein profiles separated by PAGE, isolate No.5 showed the highest number of bands (20 bands), while isolate No. 20 showed the lowest number (15 bands). The number of bands of other isolates was 16 or 17 bands. Protein profiles separated by SDS-PAGE, isolate No. 34 showed the highest number of bands (19 bands) while isolate No. 18 showed the lowest number of bands (6 bands). The other isolates showed a number of bands ranged from 13 to 17 bands. On the basis of electrophoretic dissimilarities among protein banding paterns, isolator were grouped by claster analysis and the results were expressed as phonograms. Grouping the isolates based on PAGE analysis was associated with geographic of isolates. Groping the isolates based on SDS-PAGE was associated with virulence of isolates.
4. Aqueous extracts of bougainvillea, inula, datura, eucalyptus, lantana, morus, oleander, castor bean, rosemary, salix, thuja and vinca showed toxic effect on mycelial growth and number of sclerotia/cm2 growth of S.cepivorum in vitro at 40 to 100% concentration except bougainvillea, morus, castor bean and salix at 5 to 40% and oleander and vinca at 5 to 80% concentration had no effect in this respect. Rosemary was the most effective one. Result also, revealed that all aqueous extracts decreased the number of sclerotia/cm2 growth compared with the control lantana was the most effective one in this respect.
4.1. Under greenhouse as well as field conditions in 2006/2007 and 2007/2008 growing seasons treating cloves of garlic by 40, 60 and 100% of aqueous extract of datura, eucalyplus, inula, lantana, oleander and rosemary decreased the percentage of infected plants with white rot disease as compared with the control. Rosemary was the most effective one in this respect. Treating cloves of garlic by 40, 60 and 100% of aqueous extract of datura, eucalyplus, inula, lantana, olender and rosemary greatly increased plant height, bulb diameter and bulb fresh weight as compared with the control in two growing seasons.
5. Ascorbic acid, Benzoic acid, boric acid, citric acid, oxalic acid and salicylic acid showed toxic effect on mycelial growth and number of S.cepivorum in vitro at 4 to 12mM concentrations. Ascorbic acid and salicylic acid were the most effective one. Oxalic acid had no effect in this respect. Result also, revealed that all treatments decreased the number of sclerotia/cm2 growth compared with the control
5.1.Under greenhouse as well as under field conditions in 2006/2007 and 2007/2008 growing seasons, treating cloves of garlic by 2, 4, 8 and 12mM solution of ascorbic acid and salicylic acid decreased the percentage of infected plants with white rot disease as compared with the control. Salicylic acid was the most effective one in this respect following by ascorbic acid. Results also revealed that ascorbic acid and salicylic acid caused the increased in plant height, bulb diameter and bulb fresh weight as compared with the control two growing seasons.
5.2. Treating Chinese garlic cultivar cloves with different concentrations (2, 4, 8 and 12mM) of ascorbic acid and salicylic acid increased accumulation of total phenol and leveis of PO and PPO in treated plants compared with healthy or diseased untreated plants. Treatment by salicylic acid caused the highest increased in levels of total phenol, PO and PPO following by ascorbic acid. In general, increasing concentrations of ascorbic acid and salicylic acid (from 2 up to 12mM) increased levels of total phenols, PO and PPO.
6. Studies on the effect of certain microorganisms associated with garlic rhizosphere as biocontrol agents on the caused pathogen in vitro, incidence of white rot disease growth and yield of garlic.
6.1. Thirteen isolates of fungi were isolated from the rhizosphere of Chinese garlic. Four isolates were identified as Trichoderma koningii, three isolates T.hamatum, two T.harzianum and four T.longibrachiatum and also fifteen isolates of bacteria were isolated from the rhizosphere of the same cultivar and identified as nine Bacillus subtils and six pseudomonas flourescens. All fungal and bacteria isolates obtained from the rhizosphere of garlic plants inhibited the mycelia growth of S.cepivorum in vitro and varied in their antagonistic effect.
6.2. Under greenhouse condition as well as field conditions in 2006/2207 and 2007/2008 growing seasons, infestation of the soil separately with T.koningii (isolate No. 2), T.hamatum (isolate No. 9), T.harzianum (isolate No. 13) and T.longibrachiatum (isolate No. 7), treating cloves with B.subtilis (isolate No. 7) and P.flourescens (isolate No. 13) significantly reduced the percentage of infected plants with white rot disease compared with the control.
6.3. Infection of soil separately with T.koningii, T.hamatum, T.harizamum and T.longibrachiatum as well as treating cloves with B.subtilis and P.flourescens greatly increased plant height, bulb diameter and bulb fresh weight as compared with the control in the two growing seasons.