الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
In the early history of citrus culture, especially in the western world, consumption of the fruit was principally restricted to the area in which it was produced. As faster and more convenient transportation developed, new consumer markets for citrus fruits were developed which in turn stimulated new plantings. Also, due to the great areas of the new reclaimed soils that are being mostly added to the citrus plantings not only to the suitable citrus production conditions but also to the high income of citrus orchards.In this respect, new plantings created new problems. Because, new rootstocks especially Volkamer lemon (Citrus volkameriana) has been inserted in many new plantings El-Ezaby (1994), Hassan et al. (2000) and Magaury (2011).Here, while it has long recognized that the rootstock and scion have a reciprocal influence on each other, there must be a certain affinity or congenial relationship between them for healthy development of the composite plant.Different rootstocks vary in their adaptability to grow on different soils and under different climatic conditions, as well as with different scion varieties. The rootstock and the scion interact with each other to produce stionic effects which may have a three way influence. First, the influence of the scion upon the stock, for example, the scion may increase the sodium uptake of the rootstock. Lemon scions may also increase the susceptibility of the rootstocks to gummosis. The depth of root penetration as the extent and configuration of the root system may vary on a giving rootstock depending on the scion variety budded upon it ,Castle et al. (2004).The rootstock may greatly alter the scion. It may dwarf or invigorate it. Yields may be increased or decreased; fruit size may be altered; fruit quality can be affected; hardness of the scion may also be influenced and maturity and precociousness of the scion are other considerations. In general the union of a rootstock and a scion may give rise to a combination which may be affected by an external factor which by itself affects neither the stock nor the scion individually. Such a situation exists when the virus disease Tristeza is present .The Sweet orange by itself is not measurably affected; the Sour orange by itself is not viscerally affected. However, when Sweet orange is budded upon Sour orange and Tristeza virus is present, the combination will decline or even die from the disease. If Sour orange is budded upon Sweet orange, there is no expression of the disease, even though the virus is present, Klotz (1998).Nowadays in Egypt Volkamer lemon widely used as a rootstock for different citrus cultivars in all citrus plantings in the new reclaimed soils. An advantage of this rootstock is its rapid growth, and early fruiting it being more vigorous when compared with the commonly used the Sour orange rootstock. On the other hand, the grafted trees on volkameriana bared high yield of fruits but with poor taste. In addition, exhibiting low resistance to many serious virus diseases leading to rapid reduction of fruit quality and the integrity of trees as well. Thereby, many citrus orchard in the new reclaimed areas nowadays have been removed. Also, it was observed in the mideterranean area that the Sour orange (Citrus aurantium) was resistant to many diseases especially gummosis or foot rot, Klotz and Calvan (2006).For the all above mentioned, it is ridiculous to assume that any one rootstock will have the general qualities to meet each growers needs, yet each individual growers specific rootstock need is a critical choice for the success of his orchad. Therby, the purpose of the present study, therefore, is that it will emphasize the importance of careful rootstock selection for different commercial citrus varieties. So, in our department we have planned a series of studies could be enabled us to attain reliable and convenient information about the compatibility or congeniality between the rootstock and the scion. Therefore, this study could be the first step for trying to solve the fact that: why certain combination between the rootstock and the scion as in case of volkameriana may be healthy and productive for a period of 10-15 years and then decline for unknown reasons. Other combinations as in case of Sour orange remain healthy and productive for 50 -60 years or even longer. Morphologically and physiologically traits of Sour orange and Volkameriana rootstocks and the scion are beginning these planned studies.