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Stock -Scion Relationships
A grafted or budded plant can produce unusual growth patterns which may be different from what would have occurred if each component part of a graftage viz., rootstock and scion was grown separately or when it is grafted or budded in other types of rootstocks. Some of these have major horticultural value. This varying aspect of rootstocks will influence the performance of a scion cultivar or vice versa is known as stock-scion relationship. A. Effect of stocks on scion cultivars 1. Size and growth habit:
Rootstocks do influence the nutrient status of scion also. Sathugudi orange trees have a better nutrient status of all nutrients in the leaves when it is budded on C. volkarimariana root stock than on its own rootstock or Cleopatra mandarin stocks. 6. Winter hardiness Young grapefruit trees on Rangpur lime withstand winter injury better than on rough lemon or sour orange. Sweet oranges and mandarins on trifoliate stocks were more cold hardy. 7. Disease resistanceIn citrus, considerable variability exists among the rootstocks in their response to diseases and nematodes. For instance, rough lemon rootstock is tolerant to tristeza, xyloporosis and exocortis but is susceptible to gummosis and nematode. On the other hand, troyer citrange is tolerant to gummosis but susceptible to exocortis virus disease. Similarly, guava varieties grafted on Chinese guava. (Psidium frie-drichsthalianum) resist wilt diseases and nematodes. 8. Ability to resist soil adverse conditions B. Effect of scion on rootstockAmong the citrus rootstocks, foliate orange exhibits poor ability, while sweet oranges, sour orange, rangpur lime rootstocks exhibit moderate ability to resist excess salts in the soil. Similarly, in pome fruits, variation exists among rootstocks to resist excess soil moisture or excess boron in the soil. Myrobalan plum rootstocks generally tolerate excess boron and moisture than Marianna plum root or other rootstocks' viz., peach, apricot or almond. 1. Vigour of the rootstocks: In apple, it has been found that if apple seedlings were budded with the 'Red Astrachan' apple, the rootstock produced a very fibrous root system with few tap roots. On the other hand if scion 'Goldenburg' was budded on the seedlings, they produced two or three pronged deep roots without fibrous root system. In citrus, if the scion cultivar is less vigorous than the rootstock, the rate of growth and the ultimate size of the tree is more determined by the scion rather than the rootstocks. 2. Cold hardiness of the rootstockCold hardiness of citrus roots is affected by the scion cultivar. Sour orange seedlings budded to 'Eureka' suffered much more from winter injury than the unbudded seedlings. 3. Precocity in floweringYoung mango rootstock seedlings (6 months to one year old) were found to putforth inflorescence when the branches from old trees are inarched which can be attributed to the influence of scion on the rootstock. |
Last modified: Tuesday, 18 September 2012, 9:13 AM