Induced polyploid grapes via in vitro chromosome doubling

Abstract

In vitro chromosome doubling of the 29 diploid-, 3 triploid-, and 1 tetraploid-grape accession, Vitis spp. were performed using the axillary buds of growing shoots. Treatment with 0.05% colchicine for one or two days is suitable to induce tetraploids (4X). Shoots, arising from treated-buds, often exhibited abnormal leaves, and part of them turned out to be cytochimeras (2X+4X). Additional tetraploids were isolated from parts of cytochimeras by three - divided stem cuttings. A different response to colchicine was educed in diploid cultivars, and the percentage acquisition of induced tetraploids was relatively higher in V. vinifera than in the American hybrid. Induced hexaploids (6X) were found to have a less satisfactory root system, but cytochimera, having only 3X cells in root tips, rooted well. No induced octoploids (8X) were obtained, and the growth of cytochimera, partly-having 8X cells, were slow and dwarfed. Induced tetraploids were vigorous, rooted easily, and stable over many years, whereas cytochimera of 3X+6X and 4X+8X were likely to be lost during ex vitro cultivation, reverting to the source triploid and tetraploid, respectively. A comparision of induced tetraploids and the source diploids revealed no significant difference in time of full maturity, cluster find berry shape, skin color, Brix, and acidity. However, depending on the variety, the increase in berry size in the 4X to 2X ranged from 1.1 to 1.5 fold with an average of 1.3.