Successful first and second backcrosses of S. nigrum (+) S. tuberosum somatic hybrids with both Solanum parents

Abstract

Somatic hybrids of Solanum nigrum (+) 2× potato were successfully crossed with S. nigrum and with potato. First and second backcross progeny with S. nigrum could easily be obtained. One of the BC1 genotypes was already self-fertile. Backcrosses with potato had a much lower success rate. Only pollinations with tetraploid potato resulted in seed-containing berries. Two BC1 genotypes were obtained after 4362 pollinations from which 505 ovules were cultured. The first BC1 genotype grew vigorously in vitro and in the greenhouse and flowered abundantly. The second BC1 showed many abnormalities and dropped its flowers before anthesis. The first BC1 was again crossed with tetraploid potato and in this generation also the success rate was low. Over 5000 pollinations resulted in 1750 berries from which over 3000 ovules were obtained. Twelve plants germinated from these ovules and they were not as vigorous in vitro and in vivo as the BC1 parent. Some of the BC2 genotypes were used for further backcrosses but no BC3 plants were obtained. BC1 and BC2 genotypes that resulted from the backcross program with potato were tested for resistance to Phytophthora infestans. The BC1 genotype was as resistant as the S. nigrum fusion parent, but among the eight BC2 genotypes scored six were resistant, whereas two genotypes showing lesions were susceptible.

Epidemiological importance ofSolanum sisymbriifolium,S. nigrumandS. dulcamaraas alternative hosts forPhytophthora infestans

“…One of the tested S. nigrum genotypes (Sn001) appears to carry no R‐genes effective against the P. infestans strains tested. Support for the S. nigrum R‐gene hypothesis is provided by Horsman et al . (1999), who reported on backcrosses between somatic hybrids of S. nigrum and potato to both parental species.…”

Alteration of the genomic composition of Solanum nigrum (+) potato backcross derivatives by somatic hybridization: selection of fusion hybrids by DNA measurements and GISH

“…Plant materials: The two backcross genotypes that were used in the fusion experiments, a BC 1 and a BC 2 plant, were both hybrid derivatives of S. nigrum and S. tuberosum (Horsman et al 2000). The Plant Breeding 120, 201Ð207 (2001) ã 2001 Blackwell Wissenschafts-Verlag, Berlin ISSN 0179-9541 BC 1 -6738 was the result of successful backcross of a somatic hybrid of 6x S. nigrum and a 2x potato genotype, AM10, with a tetraploid potato genotype, AM66-42.…”

“…The Plant Breeding 120, 201Ð207 (2001) ã 2001 Blackwell Wissenschafts-Verlag, Berlin ISSN 0179-9541 BC 1 -6738 was the result of successful backcross of a somatic hybrid of 6x S. nigrum and a 2x potato genotype, AM10, with a tetraploid potato genotype, AM66-42. Over 4000 pollinations and embryo rescue were needed to obtain two hexaploid BC 1 genotypes (Horsman et al 2000) of which one genotype, BC 1 -6738, was vigorous,¯owered profusely and could in turn be crossed with tetraploid potato. Over 5000 pollinations with several potato cultivars resulted in 12 BC 2 genotypes.…”

Resistance to Phytophthora infestans in somatic hybrids of Solanum nigrum L. and diploid potato

“…In 2002, pollinations with 4x cultivars yielded 98 immature seeds that were transferred onto artificial medium for further development. The pollination with potato of S. nigrum (+) S. tuberosum somatic hybrids performed by Horsman et al (2000) resulted in two BC 1 and one BC 2 clones after over 4,000 pollinations with tetraploids and the embryo rescue procedure. However, no progeny was obtained from BC 2 genotypes due to the still strong sexual crossing barrier.…”

“…Both the somatic hybrid and the BC 1 clone were as resistant as the S. nigrum fusion parent, with some necrotic spots observed at the inoculation site. Out of eight BC 2 clones, six were slightly infected with either necrotic spots or slightly necrotic regions formed, while two clones developed lesions (Horsman et al 2000).…”