Micrografting in grapevine (Vitis spp.)

Abstract

Grapes are sought after fruit grown for its high nutritional quality and taste and its use in the wine industry. Grapes are mainly cultivated in the temperate regions but some cultivars that are tolerant to high temperatures have been introduced to tropical and subtropical countries. Commercial production of grapes is approximately 60.9 metric tonnes (FAOSTAT, 2004). Over the past decade substantial increases in grapevine plantings have been driven by increasing wine exports (Pathirana & McKenzie, 2005). Amongst the genus Vitis, V. vinifera and its selections are the commercially popular table varieties as well as used in wine making. Most commercial plantations utilize direct planting of selected varieties. However, cultivated varieties of grape are susceptible to microbes, mites, insects, nematodes and more importantly to Phylloxera leading to decline in total crop productivity. Therefore it is necessary that the planting material obtained for the establishment of new vineyards must be free from diseases, especially viral. Since once a vineyard is established, minimizing losses caused by viral infection is difficult to achieve (Martelli, 1993) numerous attempts have been made at generating resistant varieties but have met with limited success. To overcome this, several methods have been developed to index the disease status of vines such as, (a) serological (Monis & Bestwick, 1996), (b) molecular (Goszczynski & Jooste, 2003), (c) woody grafting (Martelli et al., 1993) and (d) immunosorbent electron microscopy, sequential poly-acrylamide gel electrophoresis for viroids, dsRNA analysis and nucleic acid hybridization (Macquaire et al., 1993; Martelli et al., 1993). During this period, the idea has emerged 'to graft fruit-bearing scions onto resistant rootstocks to get infection free vines'.