Effect of Stocks on Scion Cultivars
1. Size and Growth Habit:
In apple, rootstocks can be classified as dwarf, semi dwarf, vigorous and very vigorous rootstocks based on their effect on a scion cultivator. If a scion is grafted on dwarf rootstocks the graft combination will be dwarf while the same cultivar grafted on very rootstock would grow very vigorously. In citrus, trifoliate orange is considered to the most dwarfing rootstock for grape fruit and sweet oranges. On the other hand, in mango all plants of a given variety are know to have the same characteristic canopy shape of the variety despite the rootstocks being of seeding origin. But recently, rootstocks of kalarady, Olour have been found to impart dwarfness in the scion cultivators. Guave cultivars grafted on Psidium puminum are found to be dwarf in stature.
2. Precocity in Flowering and Fruiting:
The time taken from plating to fruiting (Precocity) is influenced by rootstocks. Generally fruiting precocity is associated with dwarfing rootstocks and slowness to start fruiting with vigorous rootstocks. Mandarin, when grafted on Jamberi rootstocks are precious than those grafted on sweet orange or sour orange or acid lime rootstocks.
3. Fruit Set and Yield:
The rootstocks directly influence on the production of flowers and setting fruits in oriental persimmon (Diospyrous kakij cv. Hichiya). When it is grafted used as the rootstock, the fruit set is more.
The influence of rootstock on the yield performance or cultivar has been well documented in many fruit crops. Acid limes budded on rough lemon register nearly 70 percent increased yield than those budded on troyer citrange, Rangpur lime or its own rootstock. Sweet orange var. Sathgudi budded on Kichili rootstock gave higher yield than on Jamberi or on its own seeding (South India).
4. Fruit Size and Quality:
Sathgudi sweet oranges grafted on Gjanimma rootstocks produced large but poor quality fruit, while on its own roots they produced fruits with high juice content and quality. The physiological disorder ‘granulation’ in sweet orange is very low of grafted on Cleopatra mandarin seedlings, on the other hand Rough lemon seedlings, stocks induced maximum granulation. The physiological disorder ‘black end’ in Barlett Pear did not appear if Pyrus commnis was aged as the rootstock, when P. pyrisfolia was used as the rootstock. This disorder appeared, affecting fruits quality.
5. Nutrient Status of Scion:
Rootstocks do influence the nutrient status of scion also. Sathgudi sweet orange trees have a better nutrient status of all nutrients in the leaves when on its budded on C. volkarminriana rootstock than on its own rootstock or Cleopatra mandarin stocks.
6. Winter Hardlines:
Young grape fruit trees on Rangpur lime withstand winter injury better than on Rough lemon or sour on orange. Sweet orange and Mandarins on trifoliate were more cold hardy.
7. Disease Resistance:
In citrus considerable variability exists among the rootstocks in their response to diseases and nematodes. For instance Rough lemon rootstock is tolerant to tristesa, xyloprosis and exocorita but is susceptible to gummosis and nematode. On the other Troyer citrange is tolerant to gummosis but susceptible to exocorita virus disease. Similarly guava varieties grafted on Chinse Guava, (Psidium friendichthalliahum) resist wilt diseases and nematodes.
8. Ability to Resist Soil Adverse Conditions:
Among the citrus rootstocks Trifoliate orange exhibits poor ability, while sweet oranges, sour orange, Rangpur lime rootstocks exhibit moderate ability to resist excess salts in the soil. In some fruits, similarly, variation exists among rootstocks to resist excess soil moisture or excess boron in the soil. Myroblam plim rootstocks generally tolerate excess boron and moisture that Marianna pljum root or other rootstocks viz., peach, apricot or almond.