What is rootstock It is the lower portion of the graft union which develops into the root system of the grafted or budded plant.
Types of rootstock 1. Seedling rootstocks: These are developed from seed. Seedling rootstocks have deeper roots. Hence, they are strong and sturdy. Seedling rootstocks have an advantage that the chance of transmission of virus from mother plant to progeny is less. Seedling rootstock have a disadvantages of genetic variation which may lead to variation in performance of scion. Seedling rootstocks are generally used in mango, khirni , aonla, ber, bael etc.
2. Clonal rootstocks: The rootstocks are produced by vegetative propagation. Their propagation is made from layering, cuttings and micro propagation. Clonal rootstocks are uniform to mother plant. They can be utilized for their specific characteristic such as disease resistance, cold resistance, cold hardiness, stress tolerance etc. A major disadvantage of Clonal rootstock is that they retain the virus occurring in the plant part. Clonal rootstocks are common in temperate fruit crops such as apple, pear
Characteristics of an ideal rootstock: Rootstock should be vigorous, healthy and well grown. Rootstock can be easily propagated through seed or through asexual method It should exhibit a high degree of compatibility with scion cultivars and gives maximum life to trees. It should be well adapted to agro-climatic condition of the particular locality like frost, cold and heat. Rootstock should have thick bark to hold the bud It should be resistance to pest and diseases prevalent in the concerned area. It should be tolerant to adverse soil conditions like salt and drought. Rootstock have the ability to attain graftable size in short period of time
Effect of rootstock on scion 1. Influence on size and growth habit The effect of rootstock on the size and growth habit of scion cultivar is the most pronounced influence of rootstock. The rootstocks may affect the growth and the growth habit of scion cultivar invariably. In citrus, ‘Dragon Fly’ in being used universally under high density plantings in citrus because it has high potential to induce dwarfing effect in scion. Similarly ‘Creeping’ and ‘ Vellai Collumban ’ rootstock have been reported to induce dwarfness in vigorous mango cultivars like ‘ Banganpalli ’ or ‘ Alphanso ’. Likewise for guava, ‘ Pusa Srijan ’ has been recommended for as a dwarfing rootstock for Allhabad Safeda .
2. Precocity in flowering and fruiting The time taken from flowering to fruiting i.e. precocity is influenced by rootstocks. Generally fruit precocity is associated with dwarfing rootstocks and slowness to fruiting with vigorous rootstock. Mandarin, when grafted on ‘Rough lemon’ rootstock is precocious than those grafted on sweet orange or acid lime rootstock.
3. Fruit set and yield: The rootstock directly influence on the production of flower and fruit setting in oriental persimmon ( Diospyrous kaki cv . Hachiya ). When it is grafted on Dyospyrous lotus rootstock, it produces more flowers but only few mature into fruits. However, when Dyospyrous kaki is used as the rootstock, the fruit set is very high. The influence of rootstock on the yield performance of cultivar has been well documented in many fruit crops. Acid lime budded on rough lemon rootstock register 70 % increased yield than those budded on Rangpur lime or its own rootstock.
4. Influence on fruit size and quality Rootstock also influences the fruit characteristics of the scion invariably. For example if you use sour orange rootstock produces thin skinned, juicy and excellent quality fruit of scion varieties like sweet orange and grape fruit whereas rough lemon rootstocks usually produces thick, coarse skinned fruit of inferior quality of the scion cultivar. Similarly, the bitterness of the grapefruits disappears if budded on ‘Trifoliate orange’ rootstocks but it never disappears on rough lemon rootstocks. ‘
5. Nutrient status of scion Rootstock do influence the nutrient status of scion also. Sathgudi orange trees have a better nutrient status of all nutrients in the leaves when it is budded on Citrus volkarimariana root stock than on its own rootstock.
6. Winter hardiness: Young grape fruit trees on Rangpur lime withstand winter injury better than on rough lemon or sour orange rootstock. Sweet orange and mandarin on trifoliate rootstocks were more cold hardy.