الفهرس 
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Abstract
This research work was undertaken in the Plant Tissue Culture Lab.of the Tissue Culture Lab.of Hort.Dept., Faculty of Agaric., Minoufiya Univ., Shebin El-Kom in cooperation with Tissue Culture Lab., of Plant Biotechnology Dept., Genetic Engineering and Biotechnology Research Institute, Sadat City University, during the years 2010 to 2013 to investigate the procedures of tissue culture technique for clonal propagation of Banaty, Sabahy and Mobaker (guava cultivars). After surface-sterilization, the plant materials (shoot tips) were cultured in Murashige and Skoog (MS-1962) medium supplemented with various plant growth substances that favour shooting then rooting. Obtained plantlets were transplanted in the greenhouse and the survival values were recorded. The result obtained can be summarized as follows: I. Surface-sterilization: The best results were obtained when the plant materials were immersed in 0.5% sodium hypochlorite for 6-8 minutes, followed by dipping in 70% ethanol for 1- 4 minutes, then in 0.3% mercuric chloride for 1 minute. Varietal differences appeared by applying different treatments. II. Proliferation: 1- BA at 1.0 mg/l gave the best effect on shoot production per explant of the three guava cultivars. 2- Better effects were obtained when IBA at 0.02 to 2.0 mg/l was combined with BA at 1-2 mg/l. 3- Varietal differences appeared by changing the concentrations of the growth substances used. III. Rooting: 1- Application of NAA or IBA to the rooting media in the range of 0.1 to 2.0 mg/l gave better rooting than the control. Yet, the former auxin proved to be superior to IBA especially with Banaty and Sabahy cultivars. 2- Generally, increasing the concentration of either auxin tended to increase root number, while a reverse trend was true in regard to root length, especially with NAA. 3- The best rooting percentages were obtained when 0.5 to 1.0 mg/l NAA or IBA were applied to the rooting medium. 4- Combining IBA with NAA (each at 0.5 mg/l) in the rooting medium increased the rooting percentage than either auxin alone especially in the case of Mobaker shoots where the rooting value obtained was doubled by such combination. IV. Plant Survival: 1- Generally, the results indicate that the shoots treated with high concentration of IBA (up to 2.0 mg/l) survived better than those treated with such concentrations of NAA. 2- Combining IBA with NAA in the rooting medium, especially increased the survival rate of plantlets obtained with Mobaker cv. In conclusion, the results tend to indicate that it is difficult to reach a general recommendation for raising the guava cultivars included in the present study through tissue culture technique since each individual plant has different genotype make up in addition to the endogenous hormonal balance. Therefore, the explants showed measurable variation in their response to different concentrations and ratios of the growth substances included in the culture media. So, more research work is need to shows success lead to general recommendation in this aspect.