Excessive homozygosity in doubled haploids - advantages and disadvantages for plant breeding and fundamental research

The utility of haploids and DH lines for breeding programmes and basic research is discussed here. High effectiveness of haploid induction from random responding gametes and from valuable donor plants is not sufficient to ensure success in breeding. DH lines often appeared inferior to conventionally obtained inbred lines. One of the causes may be a very high level of homozygosity, in this paper referred to as excessive homozygosity. Besides, colchicine treatment as well as gametoclonal and somaclonal variation could have a negative effect on the agronomic performance of DH plants. Lack of natural selection in the first stages of haploid development is another important factor, negatively influencing haploid utility. On the other hand, there is a wide range of possibilities of using haploids as model plants for basic research. Among different applications, including mapping, genetic analysis, mutations, transformation, somatic hybridisation, biochemical and physiological studies, artificial seed production and germplasm storage, the first seems to be explored most effectively and give promising results.