Breeding for polyploidy: examples in horticultural and agricultural crops

First aimed polyploidisation in plant breeding dates back to the 1930s. Since then the technique has been a proven source for innovation in plant breeding, resulting in plants with altered morphological features, increased yield, changed fertility, etc. Recently also improved stress resistances in polyploids gets more attention. The technique of polyploidisation evolved from in vivo colchicine treatments to in vitro application of different types of antimitotic agents and the aimed use of unreduced gametes. We present four examples of polyploidy in breeding practice at ILVO. The first two examples: tetraploid clover and perennial ryegrass, are obtained through classic seedling treatment with colchicine. Tetraploid red clover offers advantages in yield and stress resistances, nevertheless tetraploids have a reduced fertility. In perennial ryegrass tetraploids are the cow’s favorites as the grass is more palatable and the digestibility is better. Therefore the share of tetraploid cultivars has increased on the recommended variety list of perennial ryegrass. A different aim for polyploidisation is found in a third example of garden Hibiscus where tetraploids were obtained by in vitro polyploidisation and by unreduced gametes. Obtained hexaploid plants show sterility which is favorable for longer lasting flowers and also the unwanted spread of seeds in the garden is stopped. As a last example stress resistance through polyploidy is presented as part of a research project. In this project diploids genotypes and tetraploids obtained from the diploid genotypes through polyploidisation are compared for biotic and (a)biotic stress resistance (also see poster: Do ploidy levels play a role in rose for (a)biotic stress resistance?).