GENERATION OF A NEW POLYPLOID GRAPE CULTIVAR BY USING HYBRID SEEDS INDUCED WITH COLCHICINE

In this report a new breeding strategy that combines traditional crossbreeding with chemically-induced mutation is described. In this strategy, germinated diploid hybrid grape seeds were treated with colchicine at two temperatures (25°C during day and 20°C at night). After the treated seedlings were planted in the field, they were first examined morphologically to check their ploidy, followed by chromosome counting using the tip-end slicing method to further confirm the ploidy of the meristematic cells of L1, L2, and L2 layers. The confirmation can lay a foundation for selective breeding leading to a new cultivar. This strategy can be used to select multiple breeding groups based on different genotypes which were produced through cross breeding, to cultivate new cultivars of polyploid grapes by chromosome doubling with chemical mutagenesis. This method can overcome the bottleneck of using vegetative induction of mutations in polyploid breeding: only a single genotype can be doubled at a time, and there is difficulty to form populations for selection. It can achieve the integration and innovation of a core technology for excessive expression of the biological effect of polyploidy and utilization of heterosis. It is also able to expand the breeding approach with large berry grapes, improve breeding efficiency and quality, and thus it is worth promoting this approach as a new breeding strategy. Application of this strategy has been successfully used to cultivate tetraploid Eurasian species of the early maturing grape cultivar ?Zaoheibao? (ploidy structure type is 4-4-4).