Plant Propogation and Nursery Management

Other Grafting Methods

3. Repair Grafting

Bridge grafting:

• Bridge grafting is basically not a method of propagation but a form of repair grafting only in plants, which have been damaged either by frost, rodents or insects. The various steps involved are shown in Fig.7.8.
• It may, however, be kept in mind that bridge grafting is only helpful if the trunk is damaged but the root system of the plant is healthy.

Fig.7.8: Different steps involved in bridge grafting A damaged plant parts B. Prepared scion stick C. Bridge grafting (Sharma and Srivastav, 2004)

• In this method, first the damaged portion of the stock is cleaned and the irregular edges of the girdled area are cut evenly.
• The scion of desired variety is inserted in such a way that it is attached at both upper and lower ends into the living bark. Similarly, it is important that scions should be inserted right side up to ensure the polarity.
• The exposed injured wood must also be covered otherwise; it may serve as an entry channel for decaying organisms.
Bracing:

• Bracing is a form of natural branch grafting that is used by fruit growers to strengthen scaffolding limbs of a tree in order to support the load of the fruit crop. In this method two strong, young lateral shoots from the limbs are to be braced.
• A rope or electrical cord is used to temporarily brace the larger limbs. The weaved smaller shoots, which will naturally graft, are tied with waxed string or poly tape to keep them together.
4. Softwood grafting

• This technique of grafting is commercially used for raising mango, sapota, tamarind and cashewnut in western India. In this technique, grafting is done with mature, procured scion on the emerging soft, coppery-red shoot of the rootstock, which is 60-70 days old.
• The basic technique involves the beheading of rootstock with a sharp knife. Then, a slit is made on the beheaded stock to insert the procured scion. The lower portion of scion is made in wedge shape so that both the faces of scion fit with the stock. Both stock and scion are tied with help of a polyethylene strip.
• The scion is then covered with a polythene bag (100 gauge) and tied with thread to keep the scion fresh till the complete union is formed (Fig.7.9). After sprouting, the bag is removed. To have better success, the leaves on the stock must be retained.
• This technique is effective in dry hot weather or in areas of low precipitation where mortality of nursery raised grafts is very high.



Fig.7.9: Steps involved in softwood grafting. A. One year old plant showing new shoot growth; B. Preparation of scion from the new growth; C Prepared root stock; D .Grafted plant ; E. Emergence of new growth in grafted plant(Sharma and Srivastav, 2004)

5. Epicotyl grafting

• It is also called as stone grafting. In this method, germinating seeds of less than two weeks old are wedge or splice grafted with mature scion. Moderate temperature and high relative humidity are major factors related to success of epicotyl grafting. For splice grafting, germinating seeds less than 2 weeks old are used as rootstock.
• A 2-3 cm long slanting cut is made in the epicotyl with a matching cut on the proximal portion of the scion and then these are tied firmly with polythene strip. In wedge grafting, the selected 2 weeks old seedlings are headed back, by retaining 6-8cm long stem with the stone.
• The longitudinal transverse cut running 4-6 cm centrally down on the beheaded rootstock is made with the help of a sharp grafting knife. A wedge shaped cut, slanting from both sides is made on the lower side of scion stick.
• The scion stick is then inserted into the saddle-like structure made on the rootstock and press properly so that cambium tissues of the rootstock and scion stick firmly and overlap each other (Fig.7.10).

Fig.7.10: Epicotyl grafting

• The union is then tied with the help of 150 gauge-polyethylene strip. This technique has been commercialized for rapid multiplication of mango in Konkan area of Maharashtra.