The Canon of Potato Science: 5. Diploid/Dihaploid Breeding

摘要

There is a diversity of potato species and their ploidy level varies enormously (i.e. the number of copies of each chromosome that they carry differs from species to species). The commercial European potato (Solatium tuberosum) is a tetraploid and thus has four copies of each chromosome - as opposed to the more frequent situation of diploids with two copies of each chromosome - as in humans. This makes breeding difficult in several ways. Firstly to get any recessive allele (form of the gene) expressed you need to have all four chromosomes having the same allele (rather than the simpler situation in the majority of species which are diploid and hence you require only the two chromosomes to be the same). Secondly when we use a genotype as a parent ifonly one chromosome has the desired allele then only one quarter of the progeny will inherit this. Lastly using many of the wild diploid species in interspecific crosses (to augment the gene pool) is complicated as sexual crossing normally produces triploids. So, one solution is to reduce the tetraploid chromosome level from four copies to the diploid level of two copies, i.e. to produce plants with the sporophytic number of chromosomes. This is possible* in potatoes and the plants can survive with thisnew chromosome level. This reduction in ploidy level can be achieved (although not always easily) by.