الفهرس 
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Abstract
Ornamental plants are hosts of a number of diseases caused by bacteria, fungi, viruses and phytoplasma; many of which have an economic impact on the crop. Root rot disease can affect a wide range of ornamentals in home and commercial landscapes, nurseries, and greenhouses. The present study was planned to identify major fungal pathogens causing root rot disease in ornamental nurseries in Egypt, and test the possibility of integration of certain cultural practices and/or bio-agent to losses caused by this disease.
Results of the present study can be summarized as follows:
Samples of diseased ornamental plants, exhibiting symptoms of root rot, i.e., Carnation, Geranium, Hollyhock, Hopbush, Orange Jessamine and Pothos were collected from different nurseries located in different regions in Egypt (Alexandria, El-Qanater El-Khaireya, Giza, Nubariya and Shoubra El-Kheima), during August 2012- March 2013.
Isolations from rotted-roots of six different ornamentals plants yielded 66 fungal isolates.
The most frequently isolated fungi were identified as Fusarium spp. (94%). These include: Fusarium semitectum, Fusarium solani, Fusarium equiseti, Fusarium chlamydosporum, Fusarium subglutinans, Fusarium scirpi, Fusarium oxysporum, Fusarium anthophilum, Fusarium verticiloides and Fusarium proliferatum. In addition, three isolates of Phytophthora spp. and an isolate of Pythium uliumum were also isolated.
Variation in pathogenicity of these isolates on Geranium and African marigold plants were established. The tested isolates caused root rot infection ranged from (0-50%), as foliar wilt severity, and (8.33-83.33%), as root rot severity, after 60 days from transplanting of geranium. While, on African marigold: foliar wilt severity ranged from (0-100%), and root rot severity ranged (25-100%), 60 days from transplanting, respectively.
A total of five fungal isolates and ten bacterial isolates were obtained from rizospheric soil of three different ornamental plants (Caranation, Geranium and Hopbush) grown in nurseries at El-Qanater El-Khaireya and Nubariya.
The bio-control ability of 16 bacterial and fungal isolates, in addition to one known isolate, was evaluated for their antagonistic activity against five tested fungal pathogens isolates, using in vitro assays. The most antagonistic bacterial isolate was Pseudomonas fluorescens (strain3339); meanwhile the most antagonistic fungal isolate was Trichoderma harzianum (TCNu 1) which greatly reduced mycelial growth of the five tested fungal pathogen isolates. T. harzianum (TCNu 1) significantly reduced mycelial growth of all tested Fusarium spp. isolates, and showed slight effect against Pythium ultimum. However, P. fluorescens (strain3339) was less effective and slightly reduced growth of all tested fungal isolates.
In greenhouse experiments with geranium transplants, P. fluorescens (strain3339) was superior to T. harzianum (TCNu 1) in reducing root rot severity. Meanwhile, with marigold, P. fluorescens (strain3339) significantly reduced foliar wilt severity, although T. harzianum (TCNu 1) gave the least root rot severity.
The effect of bio-agent treatment on growth parameters of geranium and
marigold plants was positive, where T. harzianum (TCNu 1) and
P. fluorescens (strain 3339) cause significant increase of plant height, main root length, number of leaves and fresh and dry weight of geranium plants. However, both bio-agent showed no significant effect on number of flowers of geranium plants. On marigold plants, where both T. harzianum (TCNu 1) and P. fluorescens (strain3339) greatly increased growth parameters of
marigold plants.
An experiment was conducted to evaluate the effectiveness of solarization of spent potting soil and the addition of bio-agent and organic amendments on growth and infection of marigold plants by root rot disease. Solarization of potting soil in clear, 0.1-mm-thick black polyethylene plastic
bags was solarized for 8 weeks during July and August 2015. Solarized media were compared to un-solarized soil. Before planting, two bio-control agents T. harzianum (TCNu 1) and P. fluorescens (strain3339), or cabbage and garlic dry powder or compost and vermicompost were added to solarized or un-solarized soil. The results was follows:
Total count rhizobacteria and fungi in un-solarized soil was superior to solarized soil. Which the highest bacterial (41X108 /dry soil) count was obtained from solarized soil, while the highest count of fungi (90X104 /dry soil) was obtained from un-solarized soil.
Seeding damping-off was reduced in solarized soil and the healthy survival seedling was significantly increase (100%) compared to (65%) in un-solarized soil, 14 days after seed sowing.
Trichoderma harzianum (TCNu 1) and Pseudomonas fluorescens (strain3339) were the best significant on seedling survival after 14 days by (98%) and (91%), respectively.
Root rot severity on marigold plants were greatly reduced on plants grown in solarized soil by (25.00%) compared with un-solarized soil (41.67%). However, soil amendment with cabbage, compost and vermicompost gave the best significant effect reducing root rot disease severity by (8.33-25.00%), respectively.
Growth of marigold plants was enhanced in solarized soil where main root length and number of flowers of were higher than those grown in un-solarized soil. Treatment of cabbage, compost and vermicompost gave the best significant effect and increased main root length, number of leaves of plants. However, while (TCNu 1) and (strain3339) gave the highest number of flowers.
No significant effect of soil solarization on total chlorophyll content of marigold plants. However, plants grown in soil amended with cabbage and garlic powder or compost showed high chlorophyll content, (37.97) and (37.10), respectively.
Un-solarized soil was superior to solarized soil on activity of Polyphenol Oxidase enzyme of marigold plants. Treatment with compost led to high activity of Polyphenol Oxidase enzyme (882 unit/g fw), while there was no significant effect between treatments or solarization on activity of Peroxidase enzyme of marigold plants.
In conclusion, solarization of recycled media or potting mixture for eight weeks, during summer in Egypt, in plastic bag, has prove high potential to be considered as a useful soil disinfectant, and is an inexpensive, fast, and effective technique for recycling pathogen infested soil. Combining solarization with either bio-agents or compost or vermicompost for ornamental nurseries and greenhouses production will have higher horticultural value besides being an environmentally safe and an inexpensive alternative for soil disinfestations.