الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
Citrus (Citrus sp.) is considered as one of the most important fruit crops. It is cultivated world wide especially in warm regions. Citrus occupies the third stage in the world after grapes and apples. Meanwhile, citrus is considered the first crop in Egypt for fresh use, juice and export. Citrus fruits are attacked by a number of pathogens from flowring to harvesting stages and subsequently by post-harvest pathogens that affect on fruit production at quantative and qualitative standareds. Considerable, fungal diseases, especially Alternaria rot in citrus fruit was the most important diseases wchich affect on production. The major goal of this study is to throw some lights on disease incidence, distribution and survey of Alternaria rot of citrus fruits in different growing regions, isolation and identification of the causal pathogen at microscopic examinitation and molecular level. Moreover pathogenicity tests, also varietal susceptibility. On the other side, the antagonistic action effect of different bio-agents and fungicides against the causal pathogen was studied.
The obtained results could be summarized as follows:
1- In this study data indicated that disease survey in the nurseries and orchards of citrus during 2011 till 2012 revealed that, fruit-rot disease was presented in all the observed Governorates i.e. Beheira, Kalyobia, Ismaelia, Beni-Suief, Giza, Menofia, Gharbia and Dakahlia, Governorates. Also, the highest percentage of disease survey was obtained in Beheira being (22.10%) followed by Kalyobia being (21.40%), Ismaelia (15.81%), Beni-Suief (12.70%), Giza (10.97%) and Menofia (9.60%) Governorates, while the lowest percentage of disease survey was noticed in Gharbia and Dakahlia, being (4.30 and 4.03%) respectively. Also, the results showed that, the highest percentage of Alternaria alternata fungal isolates was reached about (42.23%) compared with A. citri the percentage was (41.38 %) meanwhile, the percentage 16.39% was other fungi. The results also, indicated that the A. alternata isolates was the highest frequency isolates which isolated from
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SUMMARY
Abou-Ghanima S.F. Shehata (2018), Ph.D., Fac. Agric., Ain Shams Univ.
leaves and the percentage was reached about (12.66%) while, the highly frequency of A. citri isolates was isolated from fruits and the percentage was reached about (24.76%).
2- The tested fungal isolates were significantly various in their responsibility to cause the disease. Pathogenicity tests showed that, (S24) was the most pathogenic fungal isolate the average was 5.65 followed by (S4) 5.35 followed by (S26) the average was 5.21 then (S68) was the lowest pathogenic fungal isolate 0.22. Whilst, A. citri isolate code (S71) not gave disease symptoms when Minneola detached leaves were inoculated with A. citri.
3- Also, data of varietal susceptibility revealed that, Minneola was more susceptible cultivars to infection by all selective isolates of A. citri the (average) percentage of disease incidence was reached about (15.43%) followed by Navel orange (11.94%) and Valencia (11.86%). On the other side, more highly pathogenic isolates to all varieties were K2 followed by BW7 compared with other isolates of A. citri. Also, data of varietal reaction reveal that, Minneola tangelo was the most susceptible to infection by A. citri compared with Navel orange and Valencia percentage of disease incidence in Minneola tangelo with A. citri was 15.43% compared with Navel orange and Valencia, where the percentage were 11.94% and 11.86%, respectively.
4- Beside, Molecular biology technquies and polymerase chain reaction (PCR) clear that, 16 isolates of A. citri were identified by using 5 specific primers (ITS, OPA10-2, OPA2-1, OPA1-3and Endo-PG) but, analysis technique show that, the diversity between A. citri isolates based on two primers (OPA1-3 and Endo-PG) whlist, all isolates of A. citri were identical with primers (ITS, OPA10-2 and OPA2-1).
5- The culture filterate bioassay of Alternaria results clear that, induce and produce necrotic lesions on Minneola citrus detached leaves similar to those produced by the pathogen. Our results clearly demonstrated that the culture filtrate contained a substance that caused
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Abou-Ghanima S.F. Shehata (2018), Ph.D., Fac. Agric., Ain Shams Univ.
cell death in developed necrotic blotches when sprayed with fungus-free, culture filtrate. Development of symptoms on citrus leaves sprayed with culture filtrate showed symptoms within 48 to 72 hr, leaves subsequently wilted and died.
6- In this study, studied the effect of different solid cultures media on growth, sporulation and conidiospore measures of A. citri resulted that, potato dextrose agar (PDA) medium gave the maximium growth, the high spore production (sporulation) and the best spore size with all tested isolates of Alternaria compared with other different solid cultures media. Meanwhile, potato sucrose agar (PSA) medium gave the lowest radial growth rate and sporulation and spore size.
7- This study was extended to include the biological control of the causal pathogen of citrus fruit-rot disease. The results show that, all the tested bioagents Trichoderma harzianum, Bacillus subtilis, Omega (Bacillus spp.), T. album (Bio-Zeid) and B. megaterium (Bio-ARC) reduced percentage of infection with all the tested fungal isolates of citrus fruit-rot disease at various degrees, in vitro and in vivo trials. In case of in vitro trials, the obtained data showed that T. harzianum was more effective on the mycelium linear growth of the tested pathogenic isolate fungus than B. subtilis. Beside, the obtained data showed that, the tested bioagents were action effective against the tested causal pathogen of citrus fruit rot disease. In vitro studies proved that T. harzianum isolated was found highly effective in suppressing as abioagent against the tested causal pathogenic Alternaria isolate (Code, K2) followed by volatile of T. harzianum then B. subtilis the reduction percentage of the growth was 86.66, 86.44 and 69.44% respectively. In vivo studies also, showed that T. harzianum was the most effective bioagent against Alternaria isolate (Code, K2) followed by B. subtilis then omega whereas the reduction percentage of disease incidence was 84, 76and 72%. Whilst, B. megaterium (Bio-ARC) and T. album (Bio-Zeid) were the least effective bioagent against Alternaria isolate (Code, K2) the causal
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Abou-Ghanima S.F. Shehata (2018), Ph.D., Fac. Agric., Ain Shams Univ.
pathogen of citrus fruit rot, reduction percentage of disease incidence was 68 and 60% respectively. The biological control treatments by using fungal and bacterial bioagents was the best method to prevent environmental pollution and to keep human healthy. Biological control of plant pathogens by microorganisms has been considered a more natural and environmentally acceptable, safety, active, alternative to the existing chemical treatment methods and economically the bio-agents cost less than fungicides (Siameto, et al., 2010).
This work was planned to test some fungicides and bio-control agents to control fruit rot disease of citrus.
8- Chemical control results indicated that, A. citri was more affected fungus with three fungicides namely, Score, Montoro and Iprodione were the best fungicides based on (Ec. 50 and Ec. 90) and no observed growth of the causal fungus when these selective concentrations were used in vitro whereas at Ec. 90 were found to be 96.89, 96.89 and 329.01 respectively, and the same trend was observed in vivo trials and the reduction percentage of the disease incidence was 96.00 , 96.00 and 92.00 % respectively, while, coprax, coprareekh, and azoxystrobine were the lowest effective fungicides against isolate of A. citri (K2) causing citrus fruit rot disease in vitro and the same trend was observed in vivo trials and the reduction percentage of the disease incidence was 80.00, 80.00 and 64.00% respectively. While, Pyraclsotrobin was moderate effective when used against the pathogenic Alternaria isolate and the reduction percentage of disease incidence was (88%) and the disease incidence average was (12%) when used in vivo trial level