الفهرس 
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Abstract
The present work was carried out at the Tissue Culture Laboratory, Strawberry and Non-traditional Crops Improvement Center, Faculty of Agriculture, Ain-Shams University, during the period of 2002 to 2004 to determine the dominant bacterial and fungal contaminants through the different stages of strawberry production via tissue culture techniques.
Firstly, personal, laboratory, incubators, glasses and other equipments and/or tools used in the tissue culture were subjected to suitable sterilization means (materials) such as UV rays, spray of 3% Dettol [Liquid Antiseptic Each ml contains Chloroxylenol BP 4.8% W/V Terpineol BP 9% V/V Alcohol Absolute (Denatured) 13.1% V/V], 10% commercial Clorox [contains 5.25% sodium hypochlorite (NaOCI)], as daily or weekly regulator intervals to minimize the culture contamination as possible.
These treatments, besides traditional treatments, aid to reduce the
contamination as compared with the traditional treatments only. The results of this study can be summarized as follows:
I. The explants: homologous and high production rates of runner plants were obtained as a result of using two-years-old strawberry Camarosa and Sweet Charli cvs. runner in the micropropagation.
2. Disinfestation: beside taking precautions against any contaminants in the laboratory, facilities and plant material, some sterilizing agents were used to avoid any bacterial or fungal contamination in the tissue culture stages of strawberry explants. Concentrated fermented green tea (CFGT) gave good results as an antimicrobial either against bacterial- or fungal-contaminants (bio-antimicrobial). Somechemical sterilizing agents also gave encouraging results in this concern.
3. Isolation and identification of microbial contaminants: Seventeen bacterial isolates were assigned to major groups to the level of genera based on colony characteristics and biochemical tests. Two were classified as Agrobacterium spp.; two of them as Serratia spp.; four as Pseudomonas spp.; two as Xanthomonas spp. and one of each Enterobacter sp.; Klebsiella sp.; Corynebacterium sp.; four as Bacillus sp. Altogether a total of 15 fungal isolates were isolated. The most predominant fungus was Fusarium spp. (4) followed by Aspergillus spp. (3) Penicillium spp. (3) Alternaria spp. (2) Rhizopus sp. (1), Mucor sp. (1), and Candida sp. (1).
4. Culture filterates: Cell free culture of the most dominant bacterial and fungal isolates (of the contaminants) were obtained and mixed to tissue culture media to study their effect as promoter or inhibitor for plantlet growth development. Adding the bacterial filtrate to the culture medium caused significant enhancement in all growth parameters, except average of leaves number which increased until 100 ml then decreased. Regarding the effect of adding the fungal filtrate to the culture medium, it enhanced all growth parameters than those cultured on media + bacterial filtrate. The enhancement was increased with the increasing of fungal filtrate concentrations.
5. Antibiotics: best bacterial inhibition by antibiotics was observed when 100 and 200 ppm of either Cefotaxime or Gentamicin was used. Cefotaxime was superior in the inhibition of the bacterial contaminants at 50 ppm concentration, followed by Gentamicin at the same concentration. Meanwhile, both antibiotics used in thiswork against fungal contaminants, caused little inhibition when compared with the effect of antibiotics on bacterial contaminants. Gentamicin was more effective than Cefotaxime at all used concentrations in the suppression of fungal contaminants.
6.Bio-antimicribial: the concentrated fermented green tea (CFGT) showed antibacterial activity, but Pseudomonas showed some resistance (40%) to the CFGT followed by Bacillus (30%), Corynebacterium, Serratia (20%), and poor survival rate of Agrobacterium, Enterobacter, Klebsiella, Xanthomonas (10%) when 1.0% of CFGT per liter of medium was used. While, Pseudomonas survived (20%) and Bacillus (10%) only when 1.5% of CFGT per liter of medium was used. No growth of any investigated bacteria was observed when 2.0% of CFGT per liter of medium was used. Meanwhile, the concentrated fermented green tea (10 ml/L medium) showed antifungal activity, but Rhizopus survived (40%) to the CFGT followed by Penicillium (30%), then Aspergillus, Mucor (20%) and little growth of Alternaria, Candida, Fusarium (10%). However, no growth when either 1.5 or 2.0% of CFGT per liter of medium was used.
7.Modified culture media before acclimatization: adding 40 g sucrose to 1/2 MS (hormone-free) media gave good growth development than media supplemented with either Cefotaxime or Gentamicin antibiotics, which cause a marked reduction in the bacterial and fungal contamination. Meanwhile, the survival rate of both strawberry tested cultivars (Camarosa and Sweet Charlie) was affected by adding 40 g sucrose per litre than with the two antibiotics. However, survival rate showed increasing when sugar orantibiotics were added to culture media than control (1/2 MS hormone-free).