Comparative performance of in vitro multiplication in four grape (Vitis spp.) rootstock genotypes

The magnitude of demand for planting materials in grape, mainly for rootstock genotypes indicates that micropropagation is inevitably necessary for their mass scale propagation. Therefore, the studies on micropropagation of four genetically different grape rootstocks namely Dogridge (Vitis champini), SO4 (V. riparia× V. berlandieri), H-144 (V. vinifera × V. labrusca) and 3309 C (V. riparia × V. rupestris) were conducted to develop an optimized protocol and to compare in vitro behavior of these genotypes. Culture establishment using nodal segements was enhanced using different growth regulators. Though culture establishment increased using either BAP (Benzyl amino purine) or KIN (Kinetin) but the treatment, 2.0 mgl-1 BAP 0.2 mgl-1 NAA (Naphthalene acetic acid) was most effective with regard to enhancement in culture establishment and reduction in time to bud sprouting. Least success (38.31%) in culture establishment was observed for H-144 but it exhibited better vegetative growth and rooting among genotypes, i.e. higher shoot multiplication rate (12 micro-cuttings per culture), highest rooting (87.7%) and early root initiation (11.52 days). Addition of activated charcoal to the rooting medium was found beneficial with respect to enhancement of rooting and minimizing time to root initiation in different genotypes. Among the rootstock genotypes, 3309 C was found most responsive in terms of higher ex vitro plantlet survival (84.95%) during hardening and shorter duration required for ex vitro transfer. These results indicate that multiplication of these grape rootstocks can be performed efficiently by means of direct shoot proliferation using nodal segments from field grown vines. The influence of different factors like culture medium and genotype on the overall micropropagation of grape rootstocks is discussed.