الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
Strawberry (Fragaria x ananassa), is liable to be attacked by several diseases under Egyptian conditions, which are responsible for considerable quantitative and qualitative losses in the fruit yield. Fungi are the major causative of many diseases such as root, bud and crown rots, leaf spots, blotch, scorch and fruit rots. Some of the pathogenic fungi are restricted to attack a specific plant organ i.e. leaf, fruit, root and crown; while some others can attack two or more plant organs.
Crown rot disease are one of the most important diseases that affecting and limiting the fruit production of strawberry plantations in many parts of the world including Egypt.
The severity of crown rot diseases mainly depends on the physical and biological factors which affecting growth and development of strawberry plants like; high temperature, plant nutrient deficiencies, adverse soil conditions, damage by insects, nematodes, fungi, virus diseases and weed competition.
The present investigation was planned to study crown rot diseases in various areas of strawberry cultivations especially these areas for exportation. The results of these studies are concluded in the following:
1- The isolation of the causal pathogens of crown rot diseases was made in laboratory using typical rot symptoms during two successive seasons 2013/ 2014 and 2014/ 2015.
2- According to frequency of isolated fungi from diseased samples that collected from four villages representing to Badr district in Behaira governorate; 207 fungal isolate in the first season were isolated, while 218 fungal isolate were recorded in the second season.
3- The isolated fungi were Alternaria tenius, Alternaria solani, Colletotrichum acutatum, Colletotrichum musa, Alternaria alternate as well as Trichoderma spp in both seasons with some variations between the percentage of isolated fungi and frequency.
4- In pathogenicity tests, four isolates from the most frequent two pathogens, i.e. C. acutatum and A. tenius were tested for their virulence against three commercial strawberry cultivars, i.e. Fertona, Festival and Florida under controlled conditions in greenhouses.
5- Crown rot symptoms were noticed on Festival plants that inoculated by C. acutatum spore suspension with 100% disease severity, while it was 72.33% in the case of A. tenius on the same variety.
6- In general, the symptoms of crown rot on strawberry inoculated plants under greenhouse conditions were in high percentages in all tested cultivars inoculated by C. acutatum while it was in low percentages in the case of A. tenius.
7- In laboratory tests, strawberry fruit extract agar was the best medium for both fungal growth, while agar plant tissue juice 5% was the least effective medium.
8- The optimum temperature for fungal growth of C. acutatum was 30°C, while it was 25 °C for A. tenius.
9- The best carbon source in media was glucose for both C. acutatum and A. tenius followed by sucrose.
10- The best nitrogen source was the sodium nitrate (2g/L.) for both tested fungi (the control N source) in comparing to other 3 N sources and concentrations.
11- All tested aqueous plant extracts were greatly affected the growth of both tested pathogens under laboratory conditions. Gall extract was highly affected growth of C. acutatum. Gall extract was the best treatment in inhibition growth of A. tenius.
12- Ascorbic acid was great affected the fungus growth of both C. acutatum and A.tumius 13- Trichoderma viride was the most effective bioagent againt C. acutatum and A. tenius , followed by Bacillus subtilis.
14- All tested chemicals and fungicides affected the pathogens growth on medium under laboratory conditions.
Azoxy storbin 25% SC was recorded the maximum effect on C. acutatum growth, complete inhibition by the applied concentrations, followed by Boscalid 38% wp by the three tested concentrations.
15- Alternaria teniys also affected by both recommended fungicides as noticed in the case of C. acutatum .
16- Coccide (2000) copper hydroxide 53% wp came in the third rank after the chemical fungicides. Coccide had affected growth of both pathogens.
17- In start of field trials, vegetative and fruiting characteristics of the three cultivated strawberry varieties were very important to study pre inoculation of both pathogens using spore suspension individually.
18- Under all control treatment for plant growth, the best dose of each treatment was selected and planned to apply in large scale under field conditions to test all these treatments on plant growth and production.
19- In all treatment, leaf infection symptoms on the three tested varieties inoculated by Colletotrichum acutatum and Alternaria tenius were calculated, i.e. black spot, irregular spot, black margin, petiol lession and dead leaf.
20- Fruit also were noticed and symptoms were recorded as fruit petiol, green fruits and coloured fruits.
21- Strawberry vegetative and fruit characteristics of all three tested varieties within last 2 weeks after fungal inoculation where leaves nember, lateral branches, flower number, green fruits, coulored fruits. TSS% and fruit weight (gm).