ABSTRACT
In South America, ten Solarium species and/or subspecies, including dip loids, triploids, and tetraploids, are still cultivated (Spooner and Hijmans 2001). However, commercial potatoes are primarily tetraploid in the rest of the world. Objectives in most tetraploid cultivar breeding programs include: improving yield, reducing susceptibility to biotic and abiotic stresses, and enhancing those qualities important to the end-use market. Thus, high specific gravity (SG) and low reducing sugar content are important traits for a cultivar destined for the processing market, whereas more moderate SG, nutritional factors, taste and culinary characteristics are important traits for a cultivar destined for the fresh market. With over 200 potato species from Central and South America, the majority of them diploid (Hawkes 1990), there is a wealth of germplasm that can potentially contribute allelic diversity for traits of economic importance and for the development of new commercial cultivars. Some of the genetic manipulations necessary to incorporate genetic material from these diverse species into a tetraploid form have been discussed in other chapters of this book and are not included here, namely: introgression of genes from wild species; breeding potential and combining ability in 4x-2x crosses; and applications of cell and tissue culture. The purpose of this chapter is to review recent progress in population improvement at the diploid species level per se.
