Generation of pest resistant, diploid potato germplasm with short-day adaptation from diverse genetic stocks

Abstract

A broad range of diploid potato breeding stocks were employed to generate 2x X 2x true seed families, and subsequently, clonal selection was made under short-day conditions. The diploid parental lines used were: 1) (di)haploids from short-day adapted 4x varieties: 2) 2x wild species which are cross-compatible with cultivated diploid potatoes and (di) haploids; 3) their hybrids with 2x breeding lines which were selected under short-day conditions; 4) diploid cultivated species; and 5) long-day adapted breeding lines from programs in North America and Europe. Thirty-three diploid true seed families consisting of a total of 990 seedlings were grown in an irrigated coastal desert at La Molina, Peru in 1990. Occurrence of 2n gametes were surveyed using the seedling plants. Three hundred-fifty plants from a total of 640 evaluated by aceto-carmine glycerol stain, indicated the occurrence of 2n pollen grains at various frequencies. Eighteen of 108 plants, which were crossed by 4x males, had seed sets as female, indicating occurrence of 2n eggs. Resistance to bacterial wilt (Pseudomonas solanacearumi, potato tuber moth (Phthorimaea operculella), root-knot nematode (Meloidogyne incognita, race 3), Potato Virus Y (PVY) and potato leaf roll virus (PLRV) was evaluated. Over 100 diploid clones were identified as having resistance(s). Sixty-five clones were initially selected based on the combined traits of 2n gametes and resistance(s), followed by field evaluation for tuber appearance, stolon length and maturity using 10-hill units without replication. Nineteen clones were further tested for adaptation in terms of yield and general agronomic traits, as well as to verify their resistance(s) and occurrence of 2n gametes, between 1992-1994 at La Molina, Peru. Eleven clones were selected as parental lines which showed resistances and/or potential for use as diploid cultivars, which met the criteria for short-day adaptation, resistance(s) and crossability to tetraploid.