ABSTRACT
The cultivated potato, Solarium tuberosum L. (2n = 4x = 48), is an autotetraploid species. Asexual propagation is the normal mode of reproduc tion. Almost all genotypes are genetically heterogeneous regardless of cultivars or genetic stocks. The complexity of tetrasomic inheritance and the lack of pure lines add to the difficulty of genetic analysis of even the simplest inherited characteristics. Great progress has been achieved in manipulation of the ploidy level and its genetic consequences in the four decades since the discovery of potato haploids (Hougas and Peloquin 1957; Hougas et al. 1958). This has enabled the transfer of useful genes from related diploid and polyploid species to the cultivated tetraploid genepool. Ploidy manipulation also facilitates the investigation of tetrasomic inheritance and leads to novel strategies of gene mapping. Special mating designs accompanied by ploidy manipulation of chosen parents are used in genetic experiments and breeding for new cultivars. A number of reviews are available on ploidy manipulation and its use fulness in potato genetic and breeding research (e.g. Mendiburu and Peloquin 1976; Hermsen 1984; Iwanaga 1985; Peloquin et al. 1989; Ortiz 1998). This chapter focuses on the consequence and application of ploidy manipulation in association with autotetraploid species. Potential meth ods are examined for gene action and mapping at the tetrasomic level.
