Micrografting for Fruit Crop Improvement

Micrografting is an in vitro grafting technique which involves the placement of a meristem or shoot tip explant onto a decapitated rootstock that has been grown aseptically from seed or micropropagated cultures. Following early experiments of micrografting in ivy and chrysanthemum, the technique has been used in woody species, especially fruit trees. Major work was carried out in different Citrus species for the elimination of various viral diseases. In vitro micrografting has been used for improvement and multiplication of fruit trees as the technique has potential to combine the advantages of rapid in vitro multiplication with the increased productivity that results from grafting superior rootstock and scion combinations. Successful micrografting protocols have been developed for various fruit crops including almond, apple, cherry, chestnut, Citrus, grapes, mulberry, olive, peach, pear, pistacio, walnut, etc. Special techniques have been used for increasing the percentage of successful micrografts with the use of growth regulators, etiolation treatments, antioxidants, higher sucrose levels, silicon tubes, etc. The technique has great potential for improvement and large scale multiplication of fruit plants. It has been used on commercial scale for production of virus-free plants in fruit crops and viroid free plants in Citrus. Micrografting has also been used in prediction of incompatibility between the grafting partners, histological studies, disease indexing, production of disease-free plants particularly resistant to soil borne pathogens and multiplication of difficult to root plants.   Key words: Fruit crops, graft incompatibility, crop improvement, micrografting, propagation, shoot tip grafting.